ADC12048
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ADC12048 12-Bit Plus Sign 216 kHz 8-Channel Sampling Analog-to-Digital Converter
Check for Samples: ADC12048
1FEATURES DESCRIPTION
Operating from a single 5V power supply, the
2• 8-Channel Programmable Differential or ADC12048 is a 12 bit + sign, parallel I/O, self-
Single-Ended Multiplexer calibrating, sampling analog-to-digital converter
• Programmable Acquisition Times and User- (ADC) with an eight input fully differential analog
Controllable Throughput Rates multiplexer. The maximum sampling rate is 216 kHz.
On request, the ADC goes through a self-calibration
• Programmable Data Bus Width (8/13 bits) process that adjusts linearity, zero and full-scale
• Built-in Sample-and-Hold errors.
• Programmable Auto-Calibration and Auto-Zero The ADC12048's 8-channel multiplexer is software
cycles programmable to operate in a variety of combinations
• Low Power Standby Mode of single-ended, differential, or pseudo-differential
• No Missing Codes modes. The fully differential MUX and the 12-bit +
sign ADC allows for the difference between two
signals to be digitized.
APPLICATIONS
• Medical Instrumentation The ADC12048 can be configured to work with many
popular microprocessors/microcontrollers and DSPs
• Process Control Systems including Tl's HPC family, Intel386 and 8051,
• Test Equipment TMS320C25, Motorola MC68HC11/16, Hitachi 64180
• Data Logging and Analog Devices ADSP21xx.
• Inertial Guidance For complementary voltage references see the
LM4040, LM4041 or LM9140.
KEY SPECIFICATIONS
• (fCLK = 12 MHz)
• Resolution: 12-Bits + Sign
• 13-Bit Conversion Time: 3.6 μs, Max
• 13-Bit Throughput Rate: 216 ksamples/s, Min
• Integral Linearity Error (ILE): ±1 LSB, Max
• Single Supply: +5 V ±10%
• VIN Range: GND to VA+
• Power Consumption
– Normal Operation: 34 mW, Max
– Stand-By Mode: 75 μw, Max
1Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Copyright © 2000–2013, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
ADC12048
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Block Diagram
Connection Diagrams
Figure 1. PLCC Package Figure 2. LQFP Package
See Package Number FN0044A See Package Number PGB0044A
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PIN DESCRIPTION
PLCC Pkg. PQFP Pkg. Pin Name Description
Pin Number Pin Number
6 44 CH0 The eight analog inputs to the Multiplexer. Active channels are selected based
on the contents of bits b3–b0 of the Configuration register. Refer to INPUT
7 1 CH1 MULTIPLEXER for more details.
8 2 CH2
9 3 CH3
15 9 CH4
16 10 CH5
17 11 CH6
18 12 CH7
14 8 COM This pin is another analog input pin used as a pseudo ground when the
multiplexer is configured in single-ended mode.
13 7 VREF+ Positive reference input. The operating voltage range for this input is 1V ≤VREF+
≤VA+ (see Figure 7 and Figure 8). This pin should be bypassed to AGND at
least with a parallel combination of a 10 μF and a 0.1 μF (ceramic) capacitors.
The capacitors should be placed as close to the part as possible.
12 6 VREF−Negative reference input. The operating voltage range for this input is 0V ≤
VREF− ≤ VREF+−1 (see Figure 7 and Figure 8). This pin should be bypassed to
AGND at least with a parallel combination of a 10 μF and a 0.1 μF (ceramic)
capacitor. The capacitors should be placed as close to the part as possible.
19 13 MUX OUT−The inverting (negative) and non-inverting (positive) outputs of the multiplexer.
The analog inputs to the MUX selected by bits b3–b0 of the Configuration
21 15 MUX OUT+ register appear at these pins.
20 14 ADCIN−ADC inputs. The inverting (negative) and non-inverting (positive) inputs into the
ADC.
22 16 ADCIN+
24 18 WMODE The logic state of this pin at power-up determines which edge of the write signal
(WR) will latch in data from the data bus. If tied low, the ADC12048 will latch in
data on the rising edge of the WR signal. If tied to a logic high, data will he
latched in on the falling edge of the WR signal. The state of this pin should not
be changed after power-up.
25 19 SYNC The SYNC pin can be programmed as an input or an output. The Configuration
register's bit b8 controls the function of this pin. When programmed as an input
pin (b8 = 1), a rising edge on this pin causes the ADC's sample-and-hold to hold
the analog input signal and begin conversion. When programmed as an output
pin (b8 = 0), the SYNC pin goes high when a conversion begins and returns low
when completed.
26–31 20–25 D0–D5 13-bit Data bus of the ADC12048. D12 is the most significant bit and D0 is the
least significant. The BW (bus width) bit of the Configuration register (b12)
34–40 29–34 D6–D12 selects between an 8-bit or 13-bit data bus width. When the BW bit is cleared
(BW = 0), D7–D0 are active and D12–D8 are always in TRI-STATE. When the
BW bit is set (BW = 1), D12–D0 are active.
43 37 CLK The clock input pin used to drive the ADC12048. The operating range is 0.05
MHz to 12 MHz.
44 38 WR WR is the active low WRITE control input pin. A logic low on this pin and the CS
will enable the input buffers of the data pins D12–D0. The signal at this pin is
used by the ADC12048 to latch in data on D12–D0. The sense of the WMODE
pin at power-up will determine which edge of the WR signal the ADC12048 will
latch in data. See WMODE pin description.
1 39 RD RD is the active low read control input pin. A logic low on this pin and CS will
enable the active output buffers to drive the data bus.
2 40 CS CS is the active low Chip Select input pin. Used in conjunction with the WR and
RD signals to control the active data bus input/output buffers of the data bus.
3 41 RDY RDY is an active low output pin. The signal at this pin indicates when a
requested function has begun or ended. Refer to Functional Description and
Digital Timing Diagrams for more detail.
4 42 STDBY This is the standby active low output pin. This pin is low when the ADC12048 is
in the standby mode and high when the ADC12048 is out of the standby mode
or has been requested to leave the standby mode.
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PIN DESCRIPTION (continued)
PLCC Pkg. PQFP Pkg. Pin Name Description
Pin Number Pin Number
10 4 VA+ Analog supply input pin. The device operating supply voltage range is +5V
±10%. Accuracy is ensured only if the VA+ and VD+ are connected to the same
potential. This pin should be bypassed to AGND with a parallel combination of a
10 μF and a 0.1 μF (ceramic) capacitor. The capacitors should be placed as
close to the supply pins of the part as possible.
11 5 AGND Analog ground pin. This is the device's analog supply ground connection. It
should be connected through a low resistance and low inductance ground return
to the system power supply.
32 and 41 26 and 35 VD+ Digital supply input pins. The device operating supply voltage range is +5V
±10%. Accuracy is ensured only if the VA+ and VD+ are connected to the same
potential. This pin should be bypassed to DGND with a parallel combination of a
10 μF and a 0.1 μF (ceramic) capacitor. The capacitors should be placed as
close to the supply pins of the part as possible.
33 and 42 27 and 36 DGND Digital ground pin. This is the device's digital supply ground connection. It should
be connected through a low resistance and low inductance ground return to the
system power supply.
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings(1)(2)(3)
Supply Voltage (VA+ and VD+) 6.0V
Voltage at all Inputs −0.3V to V++ 0.3V
|VA+−VD+| 300 mV
|AGND −DGND| 300 mV
Input Current at Any Pin(4) ±30 mA
Package Input Current(4) ±120 mA
Power Dissipation at TA= 25°C(5) 875 mW
Storage Temperature −65°C to +150°C
Vapor Phase (60 sec.) 210°C
PGB Package
Lead Temperature Infared (15 sec.) 220°C
FN Package Infared (15 sec.) 300°C
ESD Susceptibility(6) 3.0 kV
(1) All voltages are measured with respect to GND, unless otherwise specified.
(2) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. For ensured specifications and test conditions, see the
Electrical Characteristics. The specified specifications apply only for the test conditions listed. Some performance characteristics may
degrade when the device is not operated under the listed test conditions.
(3) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
(4) When the input voltage (VIN) at any pin exceeds the power supply rails (VIN < GND or VIN > (VA+ or VD+)), the current at that pin should
be limited to 30 mA. The 120 mA maximum package input current limits the number of pins that can safely exceed the power supplies
with an input current of 30 mA to four.
(5) The maximum power dissipation must he derated at elevated temperatures and is dictated by TJmax, (maximum junction temperature),
θJA (package junction to ambient thermal resistance), and TA(ambient temperature). The maximum allowable power dissipation at any
temperature is PDmax = (TJmax −TA)/θJA or the number given in the Absolute Maximum Ratings, whichever is lower. For this device,
TJmax = 150°C, and the typical thermal resistance (θJA) of the ADC12048 in the FN package, when board mounted, is 55°C/W, and in
the PGB package, when board mounted, is 67.8°C/W.
(6) Human body model, 100 pF discharged through 1.5 kΩresistor.
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(7) VREFCM (Reference Voltage Common Mode Range) is defined as
ADC12048
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Operating Ratings(1)(2)(3)(4)(5)(6)
Temperature Range (Tmin ≤TA≤Tmax)−40°C ≤TA≤85°C
Supply Voltage VA+, VD+ 4.5V to 5.5V
|VA+−VD+| ≤100 mV
|AGND −DGND| ≤100 mV
VIN Voltage Range at all Inputs GND ≤VIN ≤VA+
VREF+ Input Voltage 1V ≤VREF+≤VA+
VREF−Input Voltage 0 ≤VREF− ≤ VREF+−1V
VREF+−VREF−1V ≤VREF ≤VA+
VREF Common Mode(7) 0.1 VA+≤VREFCM ≤0.6 VA+
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. For ensured specifications and test conditions, see the
Electrical Characteristics. The specified specifications apply only for the test conditions listed. Some performance characteristics may
degrade when the device is not operated under the listed test conditions.
(2) All voltages are measured with respect to GND, unless otherwise specified.
(3) Each input and output is protected by a nominal 6.5V breakdown voltage zener diode to GND; as shown below, input voltage magnitude
up to 0.3V above VA+ or 0.3V below GND will not damage the ADC12048. There are parasitic diodes that exist between the inputs and
the power supply rails and errors in the A/D conversion can occur if these diodes are forward biased by more than 50 mV. As an
example, if VA+ is 4.50 VDC, full-scale input voltage must be ≤4.55 VDC to ensure accurate conversions. See Figure 3
(4) VA+ and VD+ must be connected together to the same power supply voltage and bypassed with separate capacitors at each V+pin to
assure conversion/comparison accuracy. Refer to POWER SUPPLY CONSIDERATIONS section for a detailed discussion.
(5) Accuracy is ensured when operating at fCLK = 12 MHz.
(6) With the test condition for VREF (VREF+−VREF−) given as +4.096V, the 12-bit LSB is 1.000 mV.
Converter DC Characteristics
The following specifications apply to the ADC12048 for VA+=VD+ = 5V, VREF+ = 4.096V, VREF−= 0.0V, 12-bit + sign
conversion mode, fCLK = 12.0 MHz, RS= 25Ω, source impedance for VREF+ and VREF− ≤ 1Ω, fully differential input with fixed
2.048V common-mode voltage (VINCM), and minimum acquisition time, unless otherwise specified. Boldface limits apply for
TA= TJ= TMIN to TMAX;all other limits TA= TJ= 25°C Unit
Symbol Parameter Conditions Typical(1) Limits(2) (Limit)
Resolution with No Missing Codes After Auto-Cal 13 Bits (max)
ILE Integral Linearity Error After Auto-Cal(3)(4) ±0.6 ±1 LSB (max)
DNL Differential Non-Linearity After Auto-Cal ±1 LSB (max)
Zero Error After Auto-Cal(5)(4)
VINCM = 5.0V ±5.5 LSB (max)
VINCM = 2.048V ±2.5 LSB (max)
VINCM = 0V ±5.5 LSB (max)
Positive Full-Scale Error After Auto-Cal(3)(4) ±1.0 ±2.5 LSB (max)
Negative Full-Scale Error After Auto-Cal(3)(4) ±1.0 ±2.5 LSB (max)
DC Common Mode Error After Auto-Ca (6) ±2 ±5.5 LSB (max)
TUE Total Unadjusted Error After Auto-Cal(7) ±1 LSB
(1) Typicals are at TA= 25°C and represent most likely parametric norm.
(2) Limits are ensured to AOQL (Average Outgoing Quality Level).
(3) Positive integral linearity error is defined as the deviation of the analog value, expressed in LSBs, from the straight line that passes
through positive full-scale and zero. For negative integral linearity error, the straight line passes through negative full-scale and zero.
(4) The ADC12048's self-calibration technique ensures linearity and offset errors as specified, but noise inherent in the self-calibration
process will result in a repeatability uncertainly of ±0.20 LSB.
(5) Zero error is a measure of the deviation from the mid-scale voltage (a code of zero), expressed in LSB. It is the average value of the
code transitions between −1 to 0 and 0 to +1 (see Figure 12).
(6) The DC common-mode error is measured with both inputs shorted together and driven from 0V to 5V. The measured value is referred to
the resulting output value when the inputs are driven with a 2.5V input.
(7) Total Unadjusted Error (TUE) includes offset, full scale linearity and MUX errors.
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Power Supply Characteristics
The following specifications apply to the ADC12048 for VA+=VD+ = 5V, VREF+ = 4.096V, VREF−= 0.0V, 12-bit + sign
conversion mode, fCLK = 12.0 MHz, RS= 25Ω, source impedance for VREF+ and VREF− ≤ 1Ω, fully differential input with fixed
2.048V common-mode voltage, and minimum acquisition time, unless otherwise specified. Boldface limits apply for TA= TJ
= TMIN to TMAX;all other limits TA= TJ= 25°C Unit
Symbol Parameter Conditions Typical(1) Limits(2) (Limit)
PSS Power Supply Sensitivity VD+=VA+ = 5.0V ±10%(3)
Zero Error VREF+ = 4.096V ±0.1 LSB
Full-Scale Error VREF−= 0V ±0.5 LSB
Linearity Error ±0.1 LSB
ID+ VD+ Digital Supply Current Start Command (Performing a conversion)
with SYNC configured as an input and
driven with a 214 kHz signal. Bus width set
to 13.
fCLK = 12.0 MHz, Reset Mode 850 μA
fCLK = 12.0 MHz, Conversion 2.45 2.8 mA (max)
IA+ VA+ Analog Supply Current Start Command (Performing a conversion)
with SYNC configured as an input and
driven with a 214 kHz signal. Bus width set
to 13.
fCLK = 12.0 MHz, Reset Mode 2.3 mA
fCLK = 12.0 MHz, Conversion 2.3 4.0 mA (max)
IST Standby Supply Current Standby Mode
(ID++IA+) fCLK = Stopped 5 15 μA (max)
fCLK = 12.0 MHz 100 120 μA (max)
(1) Typicals are at TA= 25°C and represent most likely parametric norm.
(2) Limits are ensured to AOQL (Average Outgoing Quality Level).
(3) Power Supply Sensitivity is measured after an Auto-Zero and Auto Calibration cycle has been completed with VA+ and VD+ at the
specified extremes.
Analog MUX Inputs Characteristics
The following specifications apply to the ADC12048 for VA+=VD+ = 5V, VREF+ = 4.096V, VREF−= 0.0V, 12-Bit + sign
conversion mode, fCLK = 12.0 MHz, RS= 25Ω, source impedance for VREF+ and VREF+≤1Ω, fully differential input with fixed
2.048V common-mode voltage, and minimum acquisition time, unless otherwise specified. Boldface limits apply for TA= TJ
= TMIN to TMAX;all other limits TA= TJ= 25°C Unit
Symbol Parameter Conditions Typical(1) Limits(2) (Limit)
ION MUX ON Channel Leakage Current ON Channel = 5V, OFF Channel = 0V 0.05 1.0 μA (min)
ON Channel = 0V, OFF Channel = 5V −0.05 −1.0 μA (max)
IOFF MUX OFF Channel Leakage ON Channel = 5V, OFF Channel = 0V 0.05 1.0 μA (min)
Current ON Channel = 0V, OFF Channel = 5V −0.05 −1.0 μA (max)
IADCIN ADCIN Input Leakage Current 0.05 2.0 μA (max)
RON MUX On Resistance VIN = 2.5V 310 500 Ω(max)
MUX Channel-to-Channel RON VIN = 2.5V ±20% Ω
Matching
CMUX MUX Channel and COM Input 10 pF
Capacitance
CADC ADCIN Input Capacitance 70 pF
CMUXOUT MUX Output Capacitance 20 pF
(1) Typicals are at TA= 25°C and represent most likely parametric norm.
(2) Limits are ensured to AOQL (Average Outgoing Quality Level).
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Reference Inputs
The following specifications apply to the ADC12048 for VA+=VD+ = 5V, VREF+ = 4.096V, VREF−= 0.0V, 12-bit + sign
conversion mode, fCLK = 12.0 MHz, RS= 25Ω, source impedance for VREF+ and VREF− ≤ 1Ω, fully differential input with fixed
2.048V common-mode voltage, and minimum acquisition time, unless otherwise specified. Boldface limits apply for TA= TJ
= TMIN to TMAX;all other limits TA= TJ= 25°C Unit
Symbol Parameter Conditions Typical(1) Limits(2) (Limit)
IREF Reference Input Current VREF+ 4.096V, VREF−= 0V
Analog Input Signal: 1 kHz(3) 145 μA
80 kHz 136 μA
CREF Reference Input Capacitance 85 pF
(1) Typicals are at TA= 25°C and represent most likely parametric norm.
(2) Limits are ensured to AOQL (Average Outgoing Quality Level).
(3) The reference input current is a DC average current drawn by the reference input with a full-scale sinewave input. The ADC12048 is
continuously converting with a throughput rate of 206 kHz.
Digital Logic Input/Output Characteristics
The following specifications apply to the ADC12048 for VA+=VD+ = 5V, VREF+ = 4.096V, VREF−= 0.0V, 12-bit + sign
conversion mode, fCLK = 12.0 MHz, RS= 25Ω, source impedance for VREF+ and VREF− ≤ 1Ω, fully differential input with fixed
2.048V common-mode voltage, and minimum acquisition time, unless otherwise specified. Boldface limits apply for TA= TJ
= TMIN to TMAX;all other limits TA= TJ= 25°C Unit
Symbol Parameter Conditions Typical(1) Limits (2) (Limit)
VIH Logic High Input Voltage VA+=VD+ = 5.5V 2.0 V (min)
VIL Logic Low Input Voltage VA+=VD+ = 4.5V 0.8 V (max)
IIH Logic High Input Current VIN = 5V 0.035 2.0 μA (max)
IIL Logic Low Input Current VIN = 0V −0.035 −2.0 μA (max)
VOH Logic High Output Voltage VA+=VD+ = 4.5V IOUT =−1.6 mA 2.4 V (min)
VOL Logic Low Output Voltage VA+=VD+ = 4.5V IOUT = 1.6 mA 0.4 V (max)
IOFF TRI-STATE Output Leakage VOUT = 0V ±2.0 μA (max)
Current VOUT = 5V
CIN D12–D0 Input Capacitance 10 pF
(1) Typicals are at TA= 25°C and represent most likely parametric norm.
(2) Limits are ensured to AOQL (Average Outgoing Quality Level).
Converter AC Characteristics
The following specifications apply to the ADC12048 for VS+=VD+ = 5V, VREF+ = 4.096V, VREF−= 0.0V, 12-bit + sign
conversion mode, fCLK = 12.0 MHz, RS= 25Ω, source impedance for VREF+ and VREF− ≤ 1Ω, fully differential input with fixed
2.048V common-mode voltage, and minimum acquisition time, unless otherwise specified. Boldface limits apply for TA= TJ
= TMIN to TMAX;all other limits TA= TJ= 25°C Unit
Symbol Parameter Conditions Typical(1) Limits(2) (Limit)
tZAuto Zero Time 78 78 clks + 120 ns clks (max)
tCAL Full Calibration Time 4946 4946 clks + 120 ns clks (max)
50 %
CLK Duty Cycle 40 % (min)
60 % (max)
tCONV Conversion Time Sync-Out Mode 44 44 clks (max)
tAcqSYNCOUT Minimum for 13 Bits 9 9 clks + 120 ns clks (max)
Acquisition Time
(Programmable) Maximum for 13 Bits 79 79 clks + 120 ns clks (max)
(1) Typicals are at TA= 25°C and represent most likely parametric norm.
(2) Limits are ensured to AOQL (Average Outgoing Quality Level).
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Digital Timing Characteristics
The following specifications apply to the ADC12048, 13-bit data bus width, VA+=VD+ = 5V, fCLK = 12 MHz, tf= 3 ns and CL=
50 pF on data I/O lines
Symbol Units
Parameter Conditions Typical(1) Limits(2) (Limit)
tTPR Throughput Rate Sync-Out Mode (SYNC Bit =
“0”) 9 Clock Cycles of 222 kHz
Acquisition Time
tCSWR Falling Edge of CS to Falling Edge of WR 0 ns
tWRCS Active Edge of WR to Rising Edge of CS 0 ns
tWR WR Pulse Width 20 30 ns (min)
tWRSETFalling Write Setup Time WMODE = “1” 20 ns (min)
tWRHOLDFalling Write Hold Time WMODE = “1” 5ns (min)
tWRSETRising Write Setup Time WMODE = “0” 20 ns (min)
tWRHOLDRising Write Hold Time WMODE = “0” 5ns (min)
tCSRD Falling Edge of CS to Falling Edge of RD 0 ns
tRDCS Rising Edge of RD to Rising Edge of CS 0 ns
tRDDATA Falling Edge of RD to Valid Data 8-Bit Mode (BW Bit = “0”) 40 58 ns (max)
tRDDATA Falling Edge of RD to Valid Data 13-Bit Mode (BW Bit = “1”) 26 44 ns (max)
tRDHOLD Read Hold Time 23 32 ns (max)
tRDRDY Rising Edge of RD to Rising Edge of RDY 24 38 ns (max)
tWRRDY Active Edge of WR to Rising Edge of RDY WMODE = “1” 42 65 ns (max)
tSTNDBY WMODE = “0”. Writing the
Active Edge of WR to Falling Edge of STDBY Standby Command into the 200 230 ns (max)
Configuration Register
tSTDONE WMODE = “0”. Writing the
Active Edge of WR to Rising Edge of STDBY RESET Command into the 30 45 ns (max)
Configuration Register
tSTDRDY WMODE = “0”. Writing the
Active Edge of WR to Falling Edge of RDY RESET Command into the 1.4 2.5 ms (max)
Configuration Register
tSYNC Minimum SYNC Pulse Width 5 10 ns (min)
(1) Typicals are at TA= 25°C and represent most likely parametric norm.
(2) Limits are ensured to AOQL (Average Outgoing Quality Level).
Digital Timing Diagrams
Figure 3.
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Figure 4. Electrical Characteristics
Figure 5. Output Digital Code vs the Operating Input Voltage Range (General Case)
Figure 6. Output Digital Code vs the Operating Input Voltage Range for VREF = 4.096V
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Figure 9. Transfer Characteristic
Figure 10. Simplified Error vs Output Code without Auto-Calibration or Auto-Zero Cycles
Figure 11. Simplified Error vs Output Code after Auto-Calibration Cycle
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Figure 12. Offset or Zero Error Voltage (3)
Timing Diagrams
Figure 13. Sync-Out Write (WMODE = 1, BW = 1), Read and Convert Cycles
(3) Zero error is a measure of the deviation from the mid-scale voltage (a code of zero), expressed in LSB. It is the average value of the
code transitions between −1 to 0 and 0 to +1 (see Figure 12).
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Figure 14. Sync-In Write (WMODE = 1, BW = 1), Read and Convert Cycles
Figure 15. Sync-Out Write (WMODE = 0, BW = 1), Read and Convert Cycles
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Figure 16. Sync-In Write (WMODE = 0, BW = 1), Read and Convert Cycles
The MUX channel is the channel selected on the most recent write cycle.
Figure 17. Sync-Out Read and Convert Cycles.
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The MUX channel is the channel selected on the most recent write cycle.
Figure 18. Sync-In Read and Convert Cycles.
Figure 19. 8-Bit Bus Read Cycle (Sync-Out)
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Figure 20. 8-Bit Bus Read Cycle (Sync-In)
Figure 21. Write Signal Negates RDY (Writing the Standby, Auto-Cal or Auto-Zero Command)
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Typical Performance Characteristics
See Figure 4(1)
Integral Linearity Error (INL) Change Full-Scale Error Change
vs. Clock Frequency vs. Clock Frequency
Figure 23. Figure 24.
Zero Error Change Integral Linearity Error (INL) Change
vs. Clock Frequency vs. Temperature
Figure 25. Figure 26.
Full-Scale Error Change Zero Error Change
vs. Temperature vs. Temperature
Figure 27. Figure 28.
(1) The ADC12048 parts used to gather the information for these curves were auto-calibrated prior to taking the measurements at each test
condition. The auto-calibration cycle cancels any first order drifts due to test conditions. However, each measurement has a repeatability
uncertainty error of 0.2 LSB. See Note 4 under the Converter DC Characteristics Table.
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Typical Performance Characteristics (continued)
See Figure 4(1)
Integral Linearity Error (INL) Change Full-Scale Error Change
vs. Reference Voltage vs. Reference Voltage
Figure 29. Figure 30.
Zero Error Change Integral Linearity Error (INL) Change
vs. Reference Voltage vs. Supply Voltage
Figure 31. Figure 32.
Full-Scale Error Change Zero Error Change
vs. Supply Voltage vs. Supply Voltage
Figure 33. Figure 34.
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Typical Performance Characteristics
See Figure 4(1)
Supply Currents Reference Currents
vs. Clock Frequency vs. Clock Frequency
Figure 35. Figure 36.
Analog Supply Current Digital Supply Current
vs. Temperature vs. Temperature
Figure 37. Figure 38.
Full Scale Differential 1,099 Hz Full Scale Differential 18,677 Hz
Sine Wave Input Sine Wave Input
Figure 39. Figure 40.
(1) These typical curves were measured during continuous conversions with a positive half-scale DC input. A 240 ns RD pulse was applied
25 ns after the RDY signal went low. The data bus lines were loaded with 2 HC family CMOS inputs (CL∼20 pF).
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Typical Performance Characteristics (continued)
See Figure 4(1)
Full Scale Differential 38,452 Hz Full Scale Differential 79,468 Hz
Sine Wave Input Sine Wave Input
Figure 41. Figure 42.
Half Scale Differential 1 kHz Half Scale Differential 20 kHz
Sine Wave Input, fS= 153.6 kHz Sine Wave Input, fS= 153.6 kHz
Figure 43. Figure 44.
Half Scale Differential 40 kHz Half Scale Differential 75 kHz
Sine Wave Input, fS= 153.6 kHz Sine Wave Input, fS= 153.6 kHz
Figure 45. Figure 46.
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REGISTER BIT DESCRIPTION
CONFIGURATION REGISTER (Write Only)
This is a 13-bit write-only register that is used to program the functionality of the ADC12048. All data written to
the ADC12048 will always go to this register only. The contents of this register cannot be read.
MSB LSB
b12 b11 b10 b9b8b7b6b5b4b3b2b1b0
BW COMMAND FIELD SYNC HB SE ACQ TIME MUX ADDRESS
Power on State: 0100Hex
b3–b0:The MUX ADDRESS bits configure the analog input MUX. They select which input channels of the MUX
will connect to the MUXOUT+ and MUXOUT−pins. (Refer to INPUT MULTIPLEXER for more details on the
MUX.) Power-up value is 0000.
Table 1. MUX Channel Assignment
b3b2b1b0MUXOUT+ MUXOUT−
0 0 0 0 CH0 CH1
0 0 0 1 CH1 CH0
0 0 1 0 CH2 CH3
0 0 1 1 CH3 CH2
0 1 0 0 CH4 CH5
0 1 0 1 CH5 CH4
0 1 1 0 CH6 CH7
0 1 1 1 CH7 CH6
1 0 0 0 CH0 COM
1 0 0 1 CH1 COM
1 0 1 0 CH2 COM
1 0 1 1 CH3 COM
1 1 0 0 CH4 COM
1 1 0 1 CH5 COM
1 1 1 0 CH6 COM
1 1 1 1 CH7 COM
b5–b4:The ACQ TIME bits select one of four possible acquistion times in SYNC-OUT mode. (Refer to
SELECTABLE ACQUISITION TIME.)
b5b4Clocks
0 0 9
0 1 15
1 0 47
1 1 79
b6:When the Single-Ended bit (SE bit) is set, conversion results will be limited to positive values only and any
negative conversion results will appear as a code of zero in the Data register. The SE bit is cleared at power-up.
b7:The High Byte bit (HB) is meaningful only in 8-bit mode (BW bit b12 = “0”) and is a don't care condition in 13-
bit mode (BW bit b12 = “1”). This bit is used to access the upper byte of the Configuration Register in 8-bit mode.
When this bit is set and bit b12 = 0, the next byte written to the ADC12048 will program the upper byte of the
Configuration register. The HB bit will automatically be cleared when data is written to the upper byte of the
Configuration register, allowing the lower byte to be accessed with the next write. The HB bit is cleared at
power-up.
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b8:The SYNC bit. When the SYNC bit is set, the SYNC pin is programmed as an input and the converter is in
synchronous mode. In this mode a rising edge on the SYNC pin causes the ADC to hold the input signal and
begin a conversion. When b15 cleared, the SYNC pin is programmed as an output and the converter is in an
asynchronous mode. In this mode the signal at the SYNC pin indicates the status of the converter. The SYNC
pin is high when a conversion is taking place. The SYNC bit is set at power-up.
b11–b9:The command field. These bits select the mode of operation of the ADC12048. Power-up value is 000.
b11 b1b Command(1)
0 9
0 0 0 Standby command. This puts the ADC in a low power consumption mode
0 0 1 Ful-Cal command. This will cause the ADC to perform a self-calibrating cycle that will correct linearity and zero errors.
0 1 0 Auto-zero command. This will cause the ADC to perform an auto-zero cycle that corrects offset errors.
0 1 1 Reset command. This puts the ADC in an idle mode.
1 0 0 Start command. This will put the converter in a start mode, preparing it to perform a conversion. If in asynchronous mode (b8=
“0”), conversions will immediately begin after the programmed acquisition time has ended. In synchronous mode (b8= “1”),
conversions will begin after a rising edge appears on the SYNC pin.
(1) Any other values placed in the command field are meaningless. However, if a code of 101 or 110 is placed in the command field and the
CS, RD and WR go low at the same time, the ADC12048 will enter a test mode. These test modes are only to be used by the
manufacturer of this device. A hardware power-off and power-on reset must be done to get out of these test modes.
b12:This is the Bus Width (BW) bit. When this bit is a '0' the ADC12048 is configured to interface with an 8-bit
data bus; data pins D7–D0are active and pins D12–D9are in TRI-STATE. When the BW bit is a '1', the
ADC12048 is configured to interface with a 16-bit data bus and data pins D13–D0are all active. The BW bit is a
'0' at power-up.
DATA REGISTER (Read Only)
This is a 13-bit read only register that holds the 12-bit +sign conversion result in two's compliment form. All reads
performed from the ADC12048 will place the contents of this register on the data bus. When reading the data
register in 8-bit mode, the sign bit is extended (b12 through b8all contain the sign bit).
MSB LSB
b12 b11 b10 b9b8b7b6b5b4b3b2b1b0
sign Conversion Data
Power on State: 0000Hex
b11–b0:b11 is the most significant bit and b0is the least significant bit of the conversion result.
b12:This bit contains the sign of the conversion result: 0 for positive results and 1 for negative.
Functional Description
The ADC12048 is programmed through a digital interface that supports an 8-bit or 16-bit data bus. The digital
interface consists of a 13-bit data input/output bus (D12–D0), digital control signals and two internal registers: a
write only 13-bit Configuration register and a read only 13-bit Data register.
The Configuration register programs the functionality of the ADC12048. The 13 bits of the Configuration register
are divided into 7 fields. Each field controls a specific function of the ADC12048: the channel selection of the
MUX, the acquisition time, synchronous or asynchronous conversions, mode of operation and the data bus size.
Features and Operating Modes
SELECTABLE BUS WIDTH
The ADC12048 can be programmed to interface with an 8-bit or 16-bit data bus. The BW bit (b12) in the
Configuration register controls the bus size. The bus width is set to 8 bits (D7–D0are active and D12–D8are in
TRI-STATE) if the BW bit is cleared or 13 bits (D12–D0are active) if the BW bit is set. At power-up the bus width
defaults to 8 bits and any initial programming of the ADC12048 should take this into consideration.
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In 8-bit mode the Configuration register is byte accessible. The HB bit in the lower byte of the Configuration
register is used to access the upper byte. If the HB bit is set with a write to the lower byte, the next byte written
to the ADC will be placed in the upper byte of the Configuration register. After data is written to the upper byte of
the Configuration register, the HB bit will automatically be cleared, causing the next byte written to the ADC to go
to the lower byte of the Configuration register. When reading the ADC in 8-bit mode, the first read cycle places
the lower byte of the Data register on the data bus followed by the upper byte during the next read cycle.
In 13-bit mode the HB bit is a don't care condition and all bits of the data register and Configuration register are
accessible with a single read or write cycle. Since the bus width of the ADC12048 defaults to 8 bits after power-
up, the first action when 13-bit mode is desired must be set to the bus width to 13 bits.
WMODE
The WMODE pin is used to determine the active edge of the write pulse. The state of this pin determines which
edge of the WR signal will cause the ADC to latch in data. This is processor dependent. If the processor has
valid data on the bus during the falling edge of the WR signal, the WMODE pin must be tied to VD+. This will
cause the ADC to latch the data on the falling edge of the WR signal. If data is valid on the rising edge of the WR
signal, the WMODE pin must be tied to DGND causing the ADC to latch in the data on the rising edge of the WR
signal.
INPUT MULTIPLEXER
The ADC12048 has an eight channel input multiplexer with a COM input that can be used in a single-ended,
pseudo-differential or fully-differential mode. The MUX select bits (b3–b0) in the Configuration register determine
which channels will appear at the MUXOUT+ and MUXOUT−multiplexer output pins. (Refer to Register Bit
Description.) Analog signal conditioning with fixed-gain amplifiers, programmable-gain amplifiers, filters and other
processing circuits can be used at the output of the multiplexer before being applied to the ADC inputs. The
ADCIN+ and ADCIN−are the fully differential non-inverting (positive) and inverting (negative) inputs to the
analog-to-digital converter (ADC) of the ADC12048. If no external signal conditioning is required on the signal
output of the multiplexer, MUXOUT+ should be connected to ADCIN+ and MUXOUT−should be connected to
ADCIN−.
The analog input multiplexer can be set up to operate in either one of eight differential or eight single-ended (the
COM input as the zero reference) modes. In the differential mode, the analog inputs are paired as follows: CH0
with CH1, CH2 with CH3, CH4 with CH5 and CH6 with CH7. The input channel pairs can be connected to the
MUXOUT+ and MUXOUT−pins in any order. In the single-ended mode, one of the input channels, CH0 through
CH7, can be assigned to MUXOUT+ while the MUXOUT−is always assigned to the COM input.
STANDBY MODE
The ADC12048 has a low power consumption mode (75 μW @5V). This mode is entered when a Standby
command is written in the command field of the Configuration register. A logic low appearing on the STDBY
output pin indicates that the ADC12048 is in the Standby mode. Any command other than the Standby command
written to the Configuration register will get the ADC12048 out of the Standby mode. The STDBY pin will
immediately switch to a logic “1” as soon as the ADC12048 is requested to get out of the standby mode. The
RDY pin will then be asserted low when the ADC is actually out of the Standby mode and ready for normal
operation. The ADC12048 defaults to the Standby mode following a hardware power-up. This can be verified by
examining the logic low status of the STDBY pin.
SYNC/ASYNC MODE
The ADC12048 may be programmed to operate in synchronous (SYNC-IN) or asynchronous (SYNC-OUT)
mode. To enter synchronous mode, the SYNC bit in the Configuration register must be set. The ADC12048 is in
synchronous mode after a hardware power-up. In this mode, the SYNC pin is programmed as an input and
conversions are synchronized to the rising edges of the signal applied at the SYNC pin. Acquisition time can also
be controlled by the SYNC signal when in synchronous mode. Refer to Figure 14 and Figure 18. When the
SYNC bit is cleared, the ADC is in asynchronous mode and the SYNC pin is programmed as an output. In
asynchronous mode, the signal at the SYNC pin indicates the status of the converter. This pin is high when the
converter is performing a conversion. Refer to Figure 17 and Figure 15.
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SELECTABLE ACQUISITION TIME
The ADC12048's internal sample/hold circuitry samples an input voltage by connecting the input to an internal
sampling capacitor (approximately 70 pF) through an effective resistance equal to the multiplexer “On” resistance
(300Ωmax) plus the “On” resistance of the analog switch at the input to the sample/hold circuit (2500Ωtypical)
and the effective output resistance of the source. For conversion results to be accurate, the period during which
the sampling capacitor is connected to the source (the “acquisition time”) must be long enough to charge the
capacitor to within a small fraction of an LSB of the input voltage. An acquisition time of 750 ns is sufficient when
the external source resistance is less than 1 kΩand any active or reactive source circuitry settles to 12 bits in
less than 500 ns. When source resistance or source settling time increase beyond these limits, the acquisition
time must also be increased to preserve precision.
In asynchronous (SYNC-OUT) mode, the acquisition time is controlled by an internal counter. The minimum
acquisition period is 9 clock cycles, which corresponds to the nominal value of 750 ns when the clock frequency
is 12 MHz. Bits b4and b5of the Configuration Register are used to select the acquisition time from among four
possible values (9, 15, 47, or 79 clock cycles). Since acquisition time in the asynchronous mode is based on
counting clock cycles, it is also inversely proportional to clock frequency:
(1)
Note that the actual acquisition time will be longer than TACQ because acquisition begins either when the
multiplexer channel is changed or when RDY goes low, if the multiplexer channel is not changed. After a read is
performed, RDY goes high, which starts the TACQ counter (see Figure 13).
In synchronous (SYNC-IN) mode, bits b4and b5are ignored, and the acquisition time depends on the sync signal
applied at the SYNC pin. If a new MUX channel is selected at the start of the conversion, the acquisition period
begins on the active edge of the WR signal that latches in the new MUX channel. If no new MUX channel is
selected, the acquisition period begins on the falling edge of RDY, which occurs at the end of the previous
conversion (or at the end of an autozero or autocalibration procedure). The acquisition period ends when SYNC
goes high.
To estimate the acquisition time necessary for accurate conversions when the source resistance is greater than
1 kΩ, use the following expression:
where
• RSis the source resistance
• RMis the MUX “On” resistance
• RS/H is the sample/hold “On” resistance (2)
If the settling time of the source is greater than 500 ns, the acquisition time should be about 300 ns longer than
the settling time for a “well-behaved”, smooth settling characteristic.
FULL CALIBRATION CYCLE
A full calibration cycle compensates for the ADC's linearity and offset errors. The converter's DC specifications
are specified only after a full calibration has been performed. A full calibration cycle is initiated by writing a Ful-
Cal command to the ADC12048. During a full calibration, the offset error is measured eight times, averaged and
a correction coefficient is created. The offset correction coefficient is stored in an internal offset correction
register.
The overall Iinearity correction is achieved by correctng the internal DAC's capacitor mismatches. Each capacitor
is compared eight times against all remaining smaller value capacitors. The errors are averaged and correction
coefficients are created.
Once the converter has been calibrated, an arithmetic logic unit (ALU) uses the offset and linearity correction
coefficients to reduce the conversion offset and linearity errors to within specified limits.
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AUTO-ZERO CYCLE
During an auto-zero cycle, the offset is measured only once and a correction coefficient is created and stored in
an internal offset register. An auto-zero cycle is initiated by writing an Auto-Zero command to the ADC12048.
DIGITAL INTERFACE
The digital control signals are CS, RD, WR, RDY and STDBY. Specific timing relationships are associated with
the interaction of these signals. Refer to Digital Timing Diagrams for detailed timing specifications. The active low
RDY signal indicates when a certain event begins and ends. It is recommended that the ADC12048 should only
be accessed when the RDY signal is low. It is in this state that the ADC12048 is ready to accept a new
command. This will minimize the effect of noise generated by a switching data bus on the ADC. The only
exception to this is when the ADC12048 is in the standby mode at which time the RDY is high and the STDBY
signal is low. The ADC12048 is in the standby mode at power up or when a STANDBY command is issued. A
Ful-Cal, Auto-Zero, Reset or Start command will get the ADC12048 out of the standby mode. This may be
observed by monitoring the status of the RDY and STDBY signals. The RDY signal will go low and the STDBY
signal high when the ADC12048 leaves the standby mode.
The following describes the state of the digital control signals for each programmed event in both 8-bit and 13-bit
mode. RDY should be low before each command is issued except for the case when the device is in standby
mode.
FUL-CAL OR AUTO-ZERO COMMAND
8-bit mode: The first write to the ADC12048 will place the data in the lower byte of the Configuration register.
This byte must set the HB bit (b7) to allow access to the upper byte of the Configuration register during the next
write cycle. During the second write cycle, the Ful-Cal or Auto-Zero command must be issued. The edge of the
second write pulse on the WR pin will force the RDY signal high. At this time the converter begins executing a
full calibration or auto-zero cycle. The RDY signal will automatically go low when the full calibration or auto-zero
cycle is done.
13-bit mode: In a single write cycle the Ful-Cal or Auto-Zero command must be written to the ADC12048. The
edge of the WR signal will force the RDY high. At this time the converter begins executing a full calibration or
auto-zero cycle. The RDY signal will automatically go low when the full calibration or auto-zero cycle is done.
STARTING A CONVERSION: START COMMAND
In order to completely describe the events associated with the Start command, both the SYNC-OUT and SYNC-
IN modes must be considered.
SYNC-OUT/Asynchronous
8-bit mode: The first byte written to the ADC12048 should set the MUX channel, the acquisition time and the HB
bit. The second byte should clear the SYNC bit, write the START command and clear the BW bit. In order to
initiate a conversion, two reads must be performed from the ADC12048. The rising edge of the second read
pulse will force the RDY pin high and begin the programmed acquisition time selected by bits b5and b4of the
configuration register. The SYNC pin will go high indicating that a conversion sequence has begun following the
end of the acquisition period. The RDY and SYNC signal will fall low when the conversion is done. At this time
new information, such as a new MUX channel, acquisition time and operational command can be written into the
configuration register or it can remain unchanged. Assuming that the START command is in the Configuration
register, the previous conversion can be read. The first read places the lower byte of the conversion result
contained in the Data register on the data bus. The second read will place the upper byte of the conversion result
stored in the Data register on the data bus. The rising edge on the second read pulse will begin another
conversion sequence and raise the RDY and SYNC signals appropriately.
13-bit mode: The MUX channel and the acquisition time should be set, the SYNC bit cleared and the START
command issued with a single write to the ADC12048. In order to initiate a conversion, a single read must be
performed from the ADC12048. The rising edge of the read signal will force the RDY signal high and begin the
programmed acquisition time selected by bits b5and b4of the configuration register. The SYNC pin will go high
indicating that a conversion sequence has begun following the end of the acquisition period. The RDY and SYNC
signal will fall low when the conversion is done. At this time new information, such as a new MUX channel,
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acquisition time and operational command can be written into the configuration register or it can remain
unchanged. With the START command in the Configuration register, a read from the ADC12048 will place the
entire 13-bit conversion result stored in the data register on the data bus. The rising edge of the read pulse will
immediately force the RDY output high. The SYNC will then go high following the elapse of the programmed
acquisition time in the configuration register's bits b5and b4.
SYNC-IN/Synchronous
For the SYNC-IN case, it is assumed that a series of SYNC pulses at the desired sampling rate are applied at
the SYNC pin of the ADC12048.
8-bit mode: The first byte written to the ADC12048 should set the MUX channel and the HB bit. The second byte
should set the SYNC bit, write the START command and clear the BW bit.
A rising edge on the SYNC pin or the second rising edge of two consecutive reads from the ADC12048 will force
the RDY signal high. It is recommended that the action of reading from the ADC12048 (not the rising edge of the
SYNC signal) be used to raise the RDY signal. In the SYNC-IN mode, only the rising edge of the SYNC signal
will begin a conversion cycle. The rising edge of the SYNC also ends the acquisition period. The acquisition
period begins following a write cycle containing MUX channel information. The selected MUX channel is sampled
after the rising edge of the WR signal until the rising edge of the SYNC pulse, at which time the signal will be
held and conversion begins. The RDY signal will go low when the conversion is done. A new MUX channel
and/or operational command may be written into the Configuration register at this time, if needed. Two
consecutive read cycles are required to retrieve the entire 13-bit conversion result from the ADC12048's data
register. The first read will place the lower byte of the conversion result contained in the Data register on the data
bus. The second read will place the upper byte of the conversion result stored in the Data register on the data
bus. With the START command in the configuration register, the rising edge of the second read pulse will raise
the RDY signal high and begin a conversion cycle following a rising edge on the SYNC pin.
13-bit mode: The MUX channel should be selected, the SYNC bit should be set and the START command
issued with a single write to the ADC12048. A rising edge on the SYNC pin or on the RD pin will force the RDY
signal high. It is recommended that the action of reading from the ADC12048 (not the rising edge of the SYNC
signal) be used to raise the RDY signal. This will ensure that the conversion result is read during the acquisition
period of the next conversion cycle, eliminating a read from the ADC12048 while it is performing a conversion.
Noise generated by accessing the ADC12048 while it is converting may degrade the conversion result. In the
SYNC-IN mode, only the rising edge of the SYNC signal will begin a conversion cycle. The RDY signal will go
low when the conversion cycle is done. The acquisition time is controlled by the SYNC signal. The acquisition
period begins following a write cycle containing MUX channel information. The selected MUX channel is sampled
after the rising edge of the WR signal until the rising edge of the SYNC pulse, at which time the signal will be
held and conversion begins. A new MUX channel and/or operational command may be written into the
Configuration register at this time, if needed. With the START command in the Configuration register, a read from
the ADC12048 will place the entire conversion result stored in the Data register on the data bus and the rising
edge of the read pulse will force the RDY signal high. The selected MUX channel will be sampled until a rising
edge appears on the SYNC pin, at which the time sampled signal will be held and a conversion cycle started.
STANDBY COMMAND
8-bit mode: The first byte written to the ADC12048 should set the HB bit in the Configuration register (bit b7). The
second byte must issue the Standby command (bits b11, b10, b9= 0, 0, 0).
13-bit mode: The Standby command must be issued to the ADC12048 in single write (bits b11, b10, b9= 0, 0, 0).
RESET
The RESET command places the ADC12048 into a ready state and forces the RDY signal low. The RESET
command can be used to interrupt the ADC12048 while it is performing a conversion, full-calibration or auto-zero
cycle. It can also be used to get the ADC12048 out of the standby mode.
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Analog Application Information
REFERENCE VOLTAGE
The ADC12048 has two reference inputs, VREF+ and VREF−. They define the zero to full-scale range of the
analog input signals over which 4095 positive and 4096 negative codes exist. The reference inputs can be
connected to span the entire supply voltage range (VREF−= AGND, VREF+=VA+) or they can be connected to
different voltages when other input spans are required. The reference inputs of the ADC12048 have transient
capacitive switching currents. The voltage sources driving VREF+ and VREF−must have very low output
impedance and noise and must be adequately bypassed. The circuit in Figure 48 is an example of a very stable
reference source.
The ADC12048 can be used in either ratiometric or absolute reference applications. In ratiometric systems, the
analog input voltage is proportional to the voltage used for the ADC's reference voltage. This technique relaxes
the system reference requirements because the analog input voltage moves with the ADC's reference. The
system power supply can be used as the reference voltage by connecting the VREF+ pin to VA+ and the VREF−
pin to AGND. For absolute accuracy, where the analog input voltage varies between very specific voltage limits,
a time and temperature stable voltage source can be connected to the reference inputs. Typically, the reference
voltage's magnitude will require an initial adjustment to null reference voltage induced full-scale errors.
The reference voltage inputs are not fully differential. The ADC12048 will not generate correct conversions if
(VREF+) – (VREF−) is below 1V. Figure 47 shows the allowable relationship between VREF+ and VREF−.
Figure 47. VREF Operating Range
*Tantalum
**Ceramic
Figure 48. Low Drift Extremely Stable Reference Circuit
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Part Number Output Voltage Temperature
Tolerance Coefficient
LM4041CI-Adj ±0.5% ±100ppm/°C
LM4040AI-4.1 ±0.1% ±100ppm/°C
LM4050 ±0.2% ±50ppm/°C
LM4121 ±0.1% ±50ppm/°C
LM9140BYZ-4.1 ±0.5% ±25ppm/°C
Circuit of Figure 48 Adjustable ±2ppm/°C
OUTPUT DIGITAL CODE VERSUS ANALOG INPUT VOLTAGE
The ADC12048's fully differential 12-bit + sign ADC generates a two's complement output that is found by using
the equation shown below:
(3)
Round off the result to the nearest integer value between −4096 and 4095.
INPUT CURRENT
At the start of the acquisition window (tAcqSYNOUT) a charging current (due to capacitive switching) flows through
the analog input pins (CH0–CH7, ADCIN+ and ADCIN−, and the COM). The peak value of this input current will
depend on the amplitude and frequency of the input voltage applied, the source impedance and the input switch
ON resistance. With the MUXOUT+ connected to the ADCIN+ and the MUXOUT−connected to the ADCIN−the
on resistance is typically 2800Ω. Bypassing the MUX and using just the ADCIN+ and ADCIN−inputs the on
resistance is typically 2500Ω.
For low impedance voltage sources (<1000Ωfor 12 MHz operation), the input charging current will decay to a
value that will not introduce any conversion errors before the end of the default sample-and-hold (S/H)
acquisition time (9 clock cycles). For higher source impedances (>1000Ωfor 12 MHz operation), the S/H
acquisition time should be increased to allow the charging current to settle within specified limits. In
asynchronous mode, the acquisition time may be increased to 15, 47 or 79 clock cycles. If different acquisition
times are needed, the synchronous mode can be used to fully control the acquisition time.
INPUT BYPASS CAPACITANCE
External capacitors (0.01 μF–0.1 μF) can be connected between the analog input pins (CH0–CH7) and the
analog ground to filter any noise caused by inconductive pickup associated with long leads.
POWER SUPPLY CONSIDERATIONS
Decoupling and bypassing the power supply on a high resolution ADC is an important design task. Noise spikes
on the VA+ (analog supply) or VD+ (digital supply) can cause conversion errors. The analog comparator used in
the ADC will respond to power supply noise and will make erroneous conversion decisions. The ADC is
especially sensitive to power supply spikes that occur during the auto-zero or linearity calibration cycles.
The ADC12048 is designed to operate from a single +5V power supply. The separate supply and ground pins for
the analog and digital portions of the circuit allow separate external bypassing. To minimize power supply noise
and ripple, adequate bypass capacitors should be placed directly between power supply pins and their
associated grounds. Both supply pins should be connected to the same supply source. In systems with separate
analog and digital supplies, the ADC should be powered from the analog supply. At least a 10 μF tantalum
electrolytic capacitor in parallel with a 0.1 μF monolithic ceramic capacitor is recommended for bypassing each
power supply. The key consideration for these capacitors is to have low series resistance and inductance. The
capacitors should be placed as close as physically possible to the supply and ground pins with the smaller
capacitor closer to the device. The capacitors also should have the shortest possible leads in order to minimize
series lead inductance. Surface mount chip capacitors are optimal in this respect and should be used when
possible.
Copyright © 2000–2013, Texas Instruments Incorporated Submit Documentation Feedback 29
Product Folder Links: ADC12048
ADC12048
SNAS105B –APRIL 2000–REVISED MARCH 2013
www.ti.com
When the power supply regulator is not local on the board, adequate bypassing (a high value electrolytic
capacitor) should be placed at the power entry point. The value of the capacitor depends on the total supply
current of the circuits on the PC board. All supply currents should be supplied by the capacitor instead of being
drawn from the external supply lines, while the external supply charges the capacitor at a steady rate.
The ADC has two VD+ and DGND pins. It is recommended that each of these VD+ pins be separately bypassed
to DGND with a 0.1 μF plus a 10 μF capacitor. The layout diagram of Figure 49 shows the recommended
placement for the supply bypass capacitors.
PC BOARD LAYOUT AND GROUNDING
CONSIDERATlONS
To get the best possible performance from the ADC12048, the printed circuit boards should have separate
analog and digital ground planes. The reason for using two ground planes is to prevent digital and analog ground
currents from sharing the same path until they reach a very low impedance power supply point. This will prevent
noisy digital switching currents from being injected into the analog ground.
Figure 49 illustrates a favorable layout for ground planes, power supply and reference input bypass capacitors. It
shows a layout using a 44-pin PLCC socket and through-hole assembly. A similar approach should be used for
the PQFP package.
The analog ground plane should encompass the area under the analog pins and any other analog components
such as the reference circuit, input amplifiers, signal conditioning circuits, and analog signal traces.
The digital ground plane should encompass the area under the digital circuits and the digital input/output pins of
the ADC12048. Having a continuous digital ground plane under the data and clock traces is very important. This
reduces the overshoot/undershoot and high frequency ringing on these lines that can be capacitively coupled to
analog circuitry sections through stray capacitances.
The AGND and DGND in the ADC12048 are not internally connected together. They should be connected
together on the PC board right at the chip. This will provide the shortest return path for the signals being
exchanged between the internal analog and digital sections of the ADC.
It is also a good design practice to have power plane layers in the PC board. This will improve the supply
bypassing (an effective distributed capacitance between power and ground plane layers) and voltage drops on
the supply lines. However, power planes are not as essential as ground planes are for satisfactory performance.
If power planes are used, they should be separated into two planes and the area and connections should follow
the same guidelines as mentioned for the ground planes. Each power plane should be laid out over its
associated ground planes, avoiding any overlap between power and ground planes of different types. When the
power planes are not used, it is recommended to use separate supply traces for the VA+ and VD+ pins from a
low impedance supply point (the regulator output or the power entry point to the PC board). This will help ensure
that the noisy digital supply does not corrupt the analog supply.
30 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated
Product Folder Links: ADC12048
ADC12048
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SNAS105B –APRIL 2000–REVISED MARCH 2013
Figure 49. Top View of Printed Circuit Board for a 44-Pin PLCC ADC12048
When measuring AC input signals, any crosstalk between analog input/output lines and the reference lines
(CH0–CH7, MUXOUT±, ADC IN±, VREF±) should be minimized. Crosstalk is minimized by reducing any stray
capacitance between the lines. This can be done by increasing the clearance between traces, keeping the traces
as short as possible, shielding traces from each other by placing them on different sides of the AGND plane, or
running AGND traces between them.
Figure 49 also shows the reference input bypass capacitors. Here the reference inputs are considered to be
differential. The performance improves by having a 0.1 μF capacitor between the VREF+ and VREF−, and by
bypassing in a manner similar to that described for the supply pins. When a single ended reference is used,
VREF−is connected to AGND and only two capacitors are used between VREF+ and VREF−(0.1 μF + 10 μF). It is
recommended to directly connect the AGND side of these capacitors to the VREF−instead of connecting VREF−
and the ground sides of the capacitors separately to the ground planes. This provides a significantly lower-
impedance connection when using surface mount technology.
Copyright © 2000–2013, Texas Instruments Incorporated Submit Documentation Feedback 31
Product Folder Links: ADC12048
ADC12048
SNAS105B –APRIL 2000–REVISED MARCH 2013
www.ti.com
REVISION HISTORY
Changes from Revision A (March 2013) to Revision B Page
• Changed layout of National Data Sheet to TI format .......................................................................................................... 31
32 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated
Product Folder Links: ADC12048
PACKAGE OPTION ADDENDUM
www.ti.com 1-Nov-2013
Addendum-Page 1
PACKAGING INFORMATION
Orderable Device Status
(1)
Package Type Package
Drawing Pins Package
Qty Eco Plan
(2)
Lead/Ball Finish
(6)
MSL Peak Temp
(3)
Op Temp (°C) Device Marking
(4/5)
Samples
ADC12048CIV NRND PLCC FN 44 25 TBD Call TI Call TI -40 to 85 ADC12048CIV
ADC12048CIV/NOPB ACTIVE PLCC FN 44 25 Green (RoHS
& no Sb/Br) SN Level-3-245C-168 HR -40 to 85 ADC12048CIV
ADC12048CIVF NRND QFP PGB 44 96 TBD Call TI Call TI -40 to 85 ADC12048
CIVF
>R
ADC12048CIVF/NOPB ACTIVE QFP PGB 44 96 Green (RoHS
& no Sb/Br) SN Level-3-260C-168 HR -40 to 85 ADC12048
CIVF
>R
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
PACKAGE OPTION ADDENDUM
www.ti.com 1-Nov-2013
Addendum-Page 2
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
MECHANICAL DATA
MPLC004A – OCTOBER 1994
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
FN (S-PQCC-J**) PLASTIC J-LEADED CHIP CARRIER
4040005/B 03/95
20 PIN SHOWN
0.026 (0,66)
0.032 (0,81)
D2/E2
0.020 (0,51) MIN
0.180 (4,57) MAX
0.120 (3,05)
0.090 (2,29)
D2/E2
0.013 (0,33)
0.021 (0,53)
Seating Plane
MAX
D2/E2
0.219 (5,56)
0.169 (4,29)
0.319 (8,10)
0.469 (11,91)
0.569 (14,45)
0.369 (9,37)
MAX
0.356 (9,04)
0.456 (11,58)
0.656 (16,66)
0.008 (0,20) NOM
1.158 (29,41)
0.958 (24,33)
0.756 (19,20)
0.191 (4,85)
0.141 (3,58)
MIN
0.441 (11,20)
0.541 (13,74)
0.291 (7,39)
0.341 (8,66)
18
19
14
13
D
D1
13
9
E1E
4
8
MINMAXMIN
PINS
**
20
28
44
0.385 (9,78)
0.485 (12,32)
0.685 (17,40)
52
68
84 1.185 (30,10)
0.985 (25,02)
0.785 (19,94)
D/E
0.395 (10,03)
0.495 (12,57)
1.195 (30,35)
0.995 (25,27)
0.695 (17,65)
0.795 (20,19)
NO. OF D1/E1
0.350 (8,89)
0.450 (11,43)
1.150 (29,21)
0.950 (24,13)
0.650 (16,51)
0.750 (19,05)
0.004 (0,10)
M
0.007 (0,18)
0.050 (1,27)
NOTES: A. All linear dimensions are in inches (millimeters).
B. This drawing is subject to change without notice.
C. Falls within JEDEC MS-018
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