General Description
The MAX6330/MAX6331 combine a precision shunt regu-
lator with a power-on reset function in a single SOT23-3
package. They offer a low-cost method of operating small
microprocessor (µP)-based systems from high-voltage
sources, while simultaneously protecting µPs from power-
up, power-down, and brownout conditions.
Both active-low (MAX6330) and active-high (MAX6331)
push/pull output versions are available. The output
voltage has ±1.5% tolerance. The MAX6330/MAX6331
operate over a wide shunt current range from 100µA to
50mA, and offer very good transient immunity.
A 3-pin SOT23 package allows for a significant reduc-
tion in board space and improves reliability compared
to multiple-IC/discrete solutions. These devices have a
minimum order increment of 2,500 pieces.
Applications
●Controllers
●Household Appliances
●Intelligent Instruments
●Critical µP and µC Power Monitoring
●Portable/Size-Sensitive Equipment
Features
●100µA to 50mA Shunt Current Range
●Low Cost
●3-Pin SOT23 Package
●±1.5% Tolerance on Output Voltage
●Three Shunt Voltages Available: 5V, 3.3V, 3.0V
●Precision Power-On Reset Threshold:
1.5% Tolerance Available with Either
RESET (MAX6331) or RESET (MAX6330)
Outputs
●140ms Reset Timeout Period—No External
Components Required
*Insert the desired suffix letter (from the table below) into the
blank to complete the part number. These devices have a mini-
mum order increment of 2,500 pieces.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
PART* TEMP RANGE PIN-PACKAGE
MAX6330_UR-T -40°C to +85°C 3 SOT23-3
MAX6331_UR-T -40°C to +85°C 3 SOT23-3
SUFFIX
RESET
THRESHOLD
(V)
SHUNT
REGULATOR
VOLTAGE
(V)
SOT
TOP MARK
MAX6330 MAX6331
L 4.63 5.0 EKAA ELAA
T 3.06 3.3 EMAA ENAA
S 2.78 3.0 EDAA EPAA
TOP VIEW
RESET
(RESET)
1
GND
( ) ARE FOR THE MAX6331
SHUNT
MAX6330
MAX6331
SOT23-3
2
3
MAX6330
MAX6331
SHUNT
VSHUNT
ISHUNT
ILOAD
VIN
RESET
(RESET)
RESET
INPUT
GND
VCC
CL
0.1µF*
GND
µP
*SEE THE SECTION CHOOSING THE BYPASS CAPACITOR (CL)
IIN
RS
MAX6330/MAX6331 Precision Shunt Regulators with
Reset in SOT23-3
19-1348; Rev 2; 4/14
Pin Conguration
Ordering Information
Typical Operating Circuit
Terminal Voltage (with respect to GND),
All Pins Except SHUNT ..................-0.3V to (VSHUNT + 0.3V)
Input Current (ISHUNT) .......................................................60mA
Output Current (RESET/RESET) .......................................20mA
Short-Circuit Duration ................................................ Continuous
Continuous Power Dissipation
SOT23-3 (derate 4mW/°C above +70°C) .................... 320mW
Operating Temperature Range ........................... -40°C to +85°C
Storage Temperature Range ............................ -65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
(ISHUNT = 1mA, CL = 0.1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VSHUNT Regulation
Voltage
(Note 1) VSHUNT
ISHUNT =
0.1mA
to
50mA
MAX633_L
TA = +25°C 4.93 5.0 5.07
V
TA = -40°C to +85°C 4.85 5.15
MAX633_T
TA = +25°C 3.25 3.3 3.35
TA = -40°C to +85°C 3.20 3.40
MAX633_S
TA = +25°C 2.96 3.0 3.04
TA = -40°C to +85°C 2.91 3.09
Minimum VSHUNT for which
RESET is Valid (MAX6330)
TA = 0°C to +70°C 1.0 V
TA = -40°C to +85°C 1.2
VSHUNT Tempco 40 ppm/°C
Minimum Shunt Current
(Note 2)
ISHUNT(min) 100 60 µA
Maximum Shunt Current
(Note 3)
ISHUNT(max)
50
mA
Reset Threshold Voltage VTH
MAX633_L TA = +25°C 4.56 4.63 4.69
V
TA = -40°C to +85°C
4.50 4.75
MAX633_T
TA = +25°C
3.01 3.06 3.11
TA = -40°C to +85°C
2.97 3.15
MAX633_S
TA = +25°C
2.74 2.78 2.82
TA = -40°C to +85°C 2.70 2.86
Reset Threshold Tempco
40
ppm/°C
VSHUNT to Reset Delay 100mV overdrive, CL = 15pF 20 µs
Reset Pulse Width 100 140 200 ms
MAX6330/MAX6331 Precision Shunt Regulators with
Reset in SOT23-3
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Electrical Characteristics
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Absolute Maximum Ratings
(ISHUNT = 1mA, CL = 0.1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
RESET/RESET Output
Voltage Low (Note 4)
VOL
ISINK = 3.2mA
MAX6330L, VTH(min) 0.4
V
MAX6331L, VTH(max)
ISINK = 1.2mA MAX6330T/S, VTH(min)
0.3
MAX6331T/S, VTH(max)
MAX6330, VSHUNT = 1V, ISINK =
50µA,
TA = 0°C to +70°C 0.3
MAX6330, VSHUNT = 1.2V, ISINK =
50µA,
TA = -40°C to +85°C 0.3
RESET/RESET Output
Voltage High (Note 4)
VOH
ISOURCE = 800µA
MAX6331L, VTH(min)
0.8 x VSHUNT
V
MAX6330L, VTH(max)
ISOURCE = 500µA MAX6331T/S, VTH(min) 0.8 x VSHUNT
MAX6330T/S, VTH(max)
MAX6331, 1.8V < VSHUNT < VTH(min),
ISOURCE = 150µA 0.8 x VSHUNT
Note 1: It is recommended that the regulation voltage be measured using a 4-wire force-sense technique when operating at high
shunt currents. For operating at elevated temperatures, the device must be derated based on a +150°C maximum allowed
junction temperature and a maximum thermal resistance of 0.25°C/mW junction to ambient when soldered on a printed cir-
cuit board. The TA = +25°C specification over load is measured using a pulse test at 50mA with less than 5ms on time.
Note 2: Minimum shunt current required for regulated VSHUNT.
Note 3: Maximum shunt current required for regulated VSHUNT.
Note 4: In a typical application where SHUNT serves as the system voltage regulator, note that both ISOURCE for VOH and ISINK
for VOL come from VSHUNT (see the Typical Operating Circuit).
MAX6330/MAX6331 Precision Shunt Regulators with
Reset in SOT23-3
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Electrical Characteristics (continued)
(Typical Operating Circuit, CL = 0.1µF, ILOAD = 0mA, TA = +25°C, unless otherwise noted.)
VIN
50V/div
VSHUNT
2V/div
0
START-UP TRANSIENT
MAX6330 TOC07
RS = 15kΩ
50
1
0.001 1
0.10.01
STABILITY BOUNDARY CONDITIONS
10
20
30
40
MAX6330 TOC06
LOAD CAPACITANCE (µF)
SHUNT CURRENT (mA)
UNSTABLE REGION
RECOMMENDED
CAPACITOR
OPERATING
REGION
RECOMMENDED
CAPACITANCE
RECOMMENDED
CAPACITOR
0
0.0047 10.10.01
SHUNT VOLTAGE OVERSHOOT
vs. BYPASS CAPACITANCE (CL)
15
5
35
25
40
20
10
30
MAX6330 TOC5
LOAD CAPACITANCE (µF)
SHUNT VOLTAGE OVERSHOOT (mV)
ISHUNT = 5mA TO 50mA
ISHUNT = 0.1mA TO 5mA
ISHUNT = 1mA TO 1mA
0.990
0.995
1.005
1.000
1.010
-40 0-20 20 40 60 80
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
MAX6330 TOC04
TEMPERATURE (°C)
NORMALIZED RESET THRESHOLD
100
110
120
130
150
140
160
-40 0-20 20 40 60 80
POWER-UP RESET TIMEOUT
vs. TEMPERATURE
MAX6330 TOC03
TEMPERATURE (°C)
POWER-UP RESET TIMEOUT (ms)
0.990
0.995
1.000
1.005
-40 0-20 20 40 60 80
NORMALIZED SHUNT VOLTAGE
vs. TEMPERATURE
MAX6330 TOC02
TEMPERATURE (°C)
NORMALIZED SHUNT VOLTAGE
ISHUNT = 50mA
ISHUNT = 25mA
ISHUNT = 1mA
0.990
0.995
1.000
1.005
0.01 10.1 10 50
NORMALIZED SHUNT VOLTAGE
vs. SHUNT CURRENT
MAX6330 TOC01
SHUNT CURRENT (mA)
NORMALIZED SHUNT VOLTAGE
TA = +85°C
TA = -40°C
TA = +25°C
MAX6330/MAX6331 Precision Shunt Regulators with
Reset in SOT23-3
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Typical Operating Characteristics
Detailed Description
Reset Output
A microprocessor’s (µP’s) reset input starts the µP in a
known state. The MAX6330/MAX6331 µP supervisory cir-
cuits assert reset to prevent code-execution errors during
power-up, power-down, or brownout conditions.
RESET is guaranteed to be a logic low for VSHUNT > 1V.
Once VSHUNT exceeds the reset threshold, an internal
timer keeps RESET low for the reset timeout period; after
this interval, RESET goes high.
If a brownout condition occurs (VSHUNT dips below the
reset threshold), RESET goes low. When VSHUNT falls
below the reset threshold, the internal timer resets to
zero and RESET goes low. The internal timer starts after
VSHUNT returns above the reset threshold, and RESET
then remains low for the reset timeout period.
The MAX6331 has an active-high RESET output that is
the inverse of the MAX6330’s RESET output.
Shunt Regulator
The shunt regulator consists of a pass device and a
controlling circuit, as illustrated in Figure 1. The pass
device allows the regulator to sink current while regu-
lating the desired output voltage within a ±1.5% toler-
ance. The shunt current range (ISHUNT) is 100µA to
50mA.
The pass transistor in the MAX6330/MAX6331 maintains
a constant output voltage (VSHUNT) by sinking the neces-
sary amount of shunt current. When ILOAD (see Typical
Operating Circuit) is at a maximum, the shunt current is
at a minimum, and vice versa:
IIN = ISHUNT + ILOAD = (VIN - VSHUNT) / RS
Consider the following information when choosing the
external resistor RS:
1) The input voltage range, (VIN)
2) The regulated voltage, (VSHUNT)
3) The output current range, (ILOAD)
Choose RS as follows:
(VIN(max) - VSHUNT (min)) / (50mA + ILOAD(min)) ≤ RS ≤
(VIN(min) - VSHUNT (max)) / (100µA + ILOAD(max))
Choose the largest nominal resistor value for RS that
gives the lowest current consumption. Provide a safety
margin to incorporate the worst-case tolerance of the
Figure 1. Functional Diagram
PIN
NAME FUNCTION
MAX6330 MAX6331
1 1 GND Ground
2 —
RESET
Inverting Reset Output. RESET remains low while VSHUNT is below the reset threshold and
for 140ms after VSHUNT rises above the threshold.
— 2 RESET
Noninverting Reset Output. RESET remains high while VSHUNT is below the reset threshold
and for 140ms after VSHUNT rises above the threshold.
3 3 SHUNT Regulated Shunt Voltage (+5V, +3.3V, or +3.0V)
MAX6330
MAX6331
VIN
RSVSHUNT ILOAD
ISHUNT
IIN
CL
SHUNT
RESET
GENERATOR
140ms
TIMEOUT
RESET
(RESET)
1.2V
GND
( ) ARE FOR MAX6331
MAX6330/MAX6331 Precision Shunt Regulators with
Reset in SOT23-3
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Pin Description
resistor used. Ensure that the resistor’s power rating is
adequate, using the following general power equation:
PR = IIN(VIN(max) - VSHUNT)
= I2INRS
= (VIN(max) - VSHUNT)2 / RS
Applications Information
Negative-Going VSHUNT Transients
In addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, the MAX6330/
MAX6331 are relatively immune to short-duration neg-
ative-going VSHUNT transients (glitches). Additional
bypass filter capacitance mounted close to the SHUNT
pin provides additional transient immunity.
Choosing the Bypass Capacitor, CL
The bypass capacitor (CL) on the SHUNT pin can sig-
nificantly affect the device’s load-transient response, so
choose it carefully. When a load transient occurs, the
current for this load is diverted from the shunt regulator.
The maximum load current that can be diverted from the
regulator is:
ILOAD (diverted from regulator)
= ISHUNT(max) - ISHUNT(min)
= 50mA - 100µA
= 49.9mA
The shunt regulator has a finite response to this tran-
sient. The instantaneous requirements of the load
change are met by the charge on CL, resulting in over-
shoot/undershoot on VSHUNT. The magnitude of this
overshoot/undershoot increases with ISHUNT and
decreases with CL. When VSHUNT undershoots, the
shunt current decreases to where it will only draw qui-
escent current (IQ), and the shunt element turns off. At
this point, VSHUNT will slew toward VIN at the following
rate:
∆VSHUNT / ∆t = (IIN - ILOAD - 60µA) / CL
As VSHUNT rises, it will turn on the shunt regulator when
it can sink 100µA of current. A finite response time for
the shunt regulator to start up will result in a brief over-
shoot of VSHUNT before it settles into its regulation
voltage. Therefore, ILOAD should always be 100µA or
more below IIN, or VSHUNT will not recover to its regu-
lation point. To prevent this condition, be sure to select
the correct series-resistor RS value (see the Shunt
Regulator section).
Figures 2, 3, and 4 show load-transient responses for
different choices of bypass capacitors on VSHUNT.
These photos clearly illustrate the benefits and draw-
backs of the capacitor options. A smaller bypass Figure 4. Load-Transient Response with CL = 0.0047µF
Figure 3. Load-Transient Response with CL = 0.033µF
Figure 2. Load-Transient Response with CL = 0.22µF
ILOAD
2mA/div
VSHUNT
20mV/div
0
0
MAX6330 FIG 04
IIN = 2mA, ILOAD = 0 to 1.9mA
VSHUNT IS AC COUPLED
ILOAD
2mA/div
VSHUNT
20mV/div
0
0
MAX6330 FIG 03
IIN = 2mA, ILOAD = 0 to 1.9mA,
VSHUNT IS AC COUPLED
ILOAD
2mA/div
VSHUNT
20mV/div
0
0
MAX6330 FIG 02
IIN = 2mA, ILOAD = 0 to 1.9mA
VSHUNT IS AC COUPLED
MAX6330/MAX6331 Precision Shunt Regulators with
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capacitor allows a sharper drop in VSHUNT when the load
transient occurs, and will suffer from a steeper overshoot
when the device re-enters regulation. On the other hand,
the increased compensation on a larger bypass capaci-
tor will lead to a longer recovery time to regulation. The
Typical Operating Characteristics graph Overshoot vs.
Bypass Capacitance (CL) illustrates this trade-off.
If the compensation of the bypass capacitor chosen is
insufficient, the output (VSHUNT) can oscillate. Before
choosing a bypass capacitor for the desired shunt cur-
rent, observe the stability boundary conditions indicated
in the Typical Operating Characteristics. The minimum
output capacitance is 0.03µF to ensure stability over the
full load-current range.
Adding Hysteresis
In certain circumstances, the MAX6330 can be trapped
in a state that forces it to enter into and exit from a reset
condition indefinitely. This usually occurs in systems
where VSHUNT is just below the device’s trip threshold
and the system draws less quiescent current under reset
conditions than when operating out of reset. The differ-
ence in supply current when the device is in or out of reset
can translate to a significant change in the voltage drop
across RS, which the MAX6330’s built-in hysteresis may
not overcome. A 100kΩ pull-up resistor will overcome this
condition and add hysteresis (Figure 5).
Note that adding this pull-up resistor to the MAX6330 will
render RESET invalid with VSHUNT < 1V, since this out-
put loses sinking capability at this point, and the pull-up
resistor would invalidate the signal. This does not present
a problem in most applications, since most µPs and other
circuitry are inoperative when VSHUNT is below 1V.
Interfacing to µPs with
Bidirectional Reset Pins
Microprocessors with bidirectional reset pins (such as
the Motorola 68HC11 series) can contend with
MAX6330’s reset output. If, for example, the MAX6330’s
RESET output is asserted high and the µP wants to pull
it low, indeterminate logic levels may result. To correct
this, connect a 4.7kΩ resistor between the RESET output
and the µP reset I/O (Figure 6). Buffer the RESET output
to other system components. Also, RS must be sized to
compensate for additional current drawn by the µP during
the fault condition.
Shunt Current Effects
on VSHUNT and VTH
When sinking large shunt currents, power dissipation
heats the die to temperatures greater than ambient. This
may cause the VSHUNT and VTH tolerances to approach
±3% at high ambient temperatures and high shunt cur-
rents. Limit the die temperature to less than +150°C using
ΘJA = 0.25°C/mW.
Figure 6. Interfacing to µPs with Bidirectional Reset I/OFigure 5. Adding Hysteresis to the MAX6330
MAX6330
MAX6331
SHUNT
VIN
RESET
(RESET)
TO OTHER SYSTEM
COMPONENTS
CL
4.7k
RSVSHUNT
GND
VCC
GND
µP
( ) ARE FOR MAX6331
MAX6330
SHUNT
VIN
RESET RESET
INPUT
RHYST
100k
CL
RS
GND
VCC
GND
µP
MAX6330/MAX6331 Precision Shunt Regulators with
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PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
3 SOT23 U3+1 21-0151 90-0179
MAX6330/MAX6331 Precision Shunt Regulators with
Reset in SOT23-3
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Chip Information
TRANSISTOR COUNT: 283
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
2 4/14 No /V OPNs; Removed Automotive reference from Applications section 1
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAX6330/MAX6331 Precision Shunt Regulators with
Reset in SOT23-3
© 2014 Maxim Integrated Products, Inc.
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Revision History
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
