MIC2807
RF PA Power Management IC
2MHz, 500mA DC/DC w/DAC Input and
Bypass Switch, Dual Low Noise
200mA/30mA LDO Regulators
MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
January 2007 1 M9999-013007-A
General Description
The MIC2807 integrates a high performance DC/DC
converter intended for powering a power amplifier (PA) in
a mobile phone with dual low noise low dropout (LDO)
regulators for the rest of the RF section. Optimized for low
noise performance, the MIC2807 improves efficiency in the
handset without compromising quality.
The MIC2807 has a 2MHz, constant frequency pulse width
modulated (PWM) DC/DC converter designed for low
noise operation and high efficiency. The output voltage
(V
OUT
) is variable from 0.3V to the input voltage (V
IN
),
adjustable from 0.3V to 3.6V through a DAC input when
V
IN
> V
OUT
. The converter will work in a 100% duty cycle
mode to offer maximum power and efficiency in the
application. In addition to 100% duty cycle, the DC/DC
converter has a bypass mode of operation where the input
voltage node (PVIN pin) is shorted to the output voltage
node (OUT pin) through a 95m switch.
The integrated dual low noise low dropout regulators are
optimized for high PSRR capability and fast turn-on times.
The constant frequency DC/DC converter along with dual
low noise LDO regulators enables a very quiet and
efficient solution for mobile applications.
The MIC2807 is a µCap design, operating with small
ceramic output capacitors and inductors for stability,
reducing required board space and component cost and it
is available in the tiny 2.5mm x 2.8mm MLF
®
package.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
• 2.7V to 5.5V input voltage range
• Stable with ceramic output capacitors
• Tiny 17-pin 2.5mm x 2.8mm MLF
®
Package
• Thermal shutdown protection
• Current limit protection
RF PA Power Supply DC/DC Converter
• Adjustable output power supply – DAC controlled
– V
OUT
= V
DAC
x 3
• Bypass mode operation
– Internal 95m switch between PVIN and OUT pins
– V
DAC
> 1.2V
• Up to 500mA output current in PWM mode
• 100% duty cycle operation for maximum efficiency
• Tiny 4.7µH, 1µF output inductor and capacitor
• Low-noise 2MHz PWM operation
• >90% efficiency
Dual Low Noise Low Dropout Regulators
• High accuracy – ±2% over temperature
• High PSRR – greater than 70dB
• Very low output noise – 32µVrms
• LDO1 – 200mA output current capability
• LDO2 – 30mA output current capability
Applications
• CDMA2000 mobile phones
• UMTS/WCDMA mobile phones
• Wibro modules
• WiFi modules
• Power amplifier modules (PAMs) with linear PAs
Typical Application
CDMA2000/WCDMA RF Power Supply Circuit
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5
DAC VOLTAGE (V)
DC/DC Output Voltage
vs. DAC Voltage
I
OUT
= 100mA
V
IN
= 4.2V
Bypass Mode
V
OUT
= V
DAC
x 3
Micrel, Inc. MIC2807
January 2007 2 M9999-013007-A
Ordering Information
Part Number Manufacturing
Part Number LDO1/LDO2
Voltage Junction
Temp. Range
Package
Lead Finish
MIC2807-2.8/2.8YML MIC2807-MMYML 2.8V/2.8V –40°C to +125°C 17-Pin 2.5mm x 2.8mm MLF
®
Pb-Free
MIC2807-2.85/2.85YML MIC2807-NNYML 2.85V/2.85V –40°C to +125°C 17-Pin 2.5mm x 2.8mm MLF
®
Pb-Free
MIC2807-2.9/2.9YML MIC2807-OOYML 2.9V/2.9V –40°C to +125°C 17-Pin 2.5mm x 2.8mm MLF
®
Pb-Free
MIC2807-3.0/3.0YML MIC2807-PPYML 3.0V/3.0 –40°C to +125°C 17-Pin 2.5mm x 2.8mm MLF
®
Pb-Free
Pin Configur ation
17-Pin 2.5mm x 2.8mm MLF
®
(ML)
(Top View)
Pin Description
Pin Number Pin Name Pin Function
1 DAC
DAC Control Input (Analog Voltage Input). Provides control of output voltage of DC/DC converter.
The output voltage is 3x’s the DAC voltage (Ex. 0.5V
DAC
= 1.5V
OUT
) when V
IN
> V
OUT
. Bypass mode is
enabled when the DAC voltage exceeds 1.2V or V
IN
V
OUT
. V
OUT
= V
DAC
x 3.
2 BYP Filter capacitor for LDO1 and LDO2 internal voltage reference, connect capacitor to ground.
3 AGND Signal ground of chip.
4 EN2 Enables the LDO2 regulator.
5 VIN LDO1 and LDO2 Supply Voltage. Must be connected to PIN 15.
6 LDO1 Output of the LDO1.
7 LDO2 Output of the LDO2.
8, 9 OUT Drain of internal bypass switch, also serves as feedback for the internal regulator.
10 PGND Power ground.
11 SW Switch: Internal power MOSFET output switches of DC/DC converter.
12 PVIN Supply Voltage: Requires bypass capacitor to ground.
13 EN1 Enables LDO1 Regulator.
14 EN Enables the DC/DC Converter.
15 AVIN
Supply voltage for DC/DC converter control circuitry and reference voltage circuit. Must be connected
to PIN 5.
16, 17 NC No Connect.
Micrel, Inc. MIC2807
January 2007 3 M9999-013007-A
Absolute Maximum Ratings(1)
Supply Voltage (PV
IN
, AV
IN
, V
IN
) ............................ 0V to 6V
Output Switch Voltage (V
SW
). ...........................................6V
DAC Input Voltage (V
DAC
)....................................... 0V to V
IN
Logic Input Voltage (V
EN
, V
EN1
, V
EN2
) ..................... 0V to V
IN
Power Dissipation
(3)
...................................Internally Limited
Storage Temperature (T
s
) .........................–65°C to +150°C
ESD Rating
(4)
................................................................ ±2kV
Operating Ratings(2)
Supply Voltage (PV
IN
, AV
IN
, V
IN
) ...................... 2.7V to 5.5V
Output Voltage (V
OUT
) ............................................ 0V to V
IN
Enable Voltage (V
EN
, V
EN1
, V
EN2
)............................ 0V to V
IN
DAC Input Voltage (V
DAC
).................................... 0.1V to V
IN
Junction Temperature (T
J
) ........................–40°C to +125°C
Thermal Resistance
2.5x2.8mm MLF-17 (θ
JA
) ...................................70°C/W
Electrical Characteristics(5)
DC/DC Converter
V
IN
= PV
IN
= AV
IN
= V
EN
= 3.6V; V
DAC
= 0.6V; V
EN1
= V
EN2
= 0V; L = 4.7µH; C
OUT
= 1µF; T
A
= 25°C, bold values indicate
–40°C< T
J
< +125°C, unless noted.
LDO1/LDO2
V
IN
= V
EN1
= V
EN2
= 3.6V; C
OUTLDO1
= 2.2µF; V
EN
= 0V; C
OUTLDO2
= 1µF; I
OUT
= 100µA; T
A
= 25°C, bold values indicate
–40°C< T
J
< +125°C, unless noted.
Parameter Condition Min Typ Max Units
MIC2807
Supply Voltage Range 2.7 5.5
V
Total Quiescent Current V
EN
= V
EN1
= V
EN2
= 3.6V
V
DAC
= 0.6V (DC/DC: not switching) 480 µA
Logic Low 0.4 V Enable Pin Threshold
Logic High 1.3 V
Enable Pin Hysteresis 30 mV
Enable Pin Input Current 0.01 1 µA
Under-Voltage
Lockout Threshold
(turn-on) 2.6
2.7 V
UVLO Hysteresis 85 mV
Shutdown Temperature 160 ºC
Shutdown Temperature
Hysteresis
20 ºC
Total Shutdown Current V
EN
= V
EN1
= V
EN2
= 0V 1 5 µA
DC/DC Converter [V
EN1
= V
EN2
= 0V]
Maximum Duty Cycle 100 %
Bypass Quiescent
Current
V
DAC
= 1.3V 490 650 µA
Quiescent Current V
DAC
= 0.6V (regulator on, not switching) 360 450 µA
Output Voltage V
DAC
= 0.6V, I
LOAD
= 0mA 1.746 1.8 1.854 V
Output Voltage
Line Regulation
3.0V< V
IN
< 4.5, I
LOAD
= 10mA 0.05 0.5 %/V
Output Voltage
Load Regulation
0mA < I
OUT
< 400mA 0.2 1 %
Switch On-Resistance I
SW
= -100mA, High-Side Switch
I
SW
= 100mA, Low-Side Switch
0.55
0.6
0.75
0.85
Current Limit
(Peak SW Current)
0.65 0.85 1.6 A
Frequency 1.8 2 2.2 MHz
Micrel, Inc. MIC2807
January 2007 4 M9999-013007-A
Parameter Condition Min Typ Max Units
Turn-On Time I
OUT
= 100µA 25 50 µs
DAC Input Current 0.15 2 µA
Output Voltage/
DAC Voltage
(internally set) 3 V/V
Bypass Switch
Threshold
DAC Voltage required to enable bypass mode 1.176 1.2 1.224 V
Bypass Switch
Hysteresis
35 mV
Bypass Transition Time Delay from V
DAC
= 1.3V to V
OUT
= 0.90V
IN
10
40 µs
Bypass Switch
On-Resistance
V
IN
= 3.0V, I
BYPASS
= 100mA 95 150 m
Bypass Switch Leakage 5 µA
Bypass Over-Current
Limit
1 1.4 2.5 A
Current Limit Retry Time 32 µs
Current Limit Retry
Duty Cycle
12.5 %
LDO1/LDO2 [V
EN
= 0V]
Total Ground Current
(8)
V
EN1
= V
EN2
= 3.6V 220 µA
Turn-on Time LDO1 or LDO2; C
BYP
= 0.1µF 30 100 µs
LDO1 [V
EN
= 0V]
Variation from nominal V
OUT
–1 +1 % Output Voltage Accuracy
–40°C to +125°C –2 +2 %
Line Regulation V
IN
= V
OUT
+1V to 5.5V 0.02 0.3 %/V
Load Regulation
(6)
I
OUT
= 100µA to 200mA 0.2 0.5 %
Dropout Voltage
(7)
I
OUT
= 50mA; V
OUT
> 2.8V
I
OUT
= 150mA; V
OUT
> 2.8V
I
OUT
= 200mA; V
OUT
> 2.8V
20
55
70
120
mV
mV
mV
Ground Pin Current
(8)
I
OUT
= 0mA; EN2 = GND 190 300 µA
Ripple Rejection f = up to 1kHz; C
BYP
= 0.1µF
f = 1kHz – 20kHz; C
BYP
= 0.1µF
70
45
dB
dB
Current Limit V
OUT
= 0V 225 300 700 mA
Output Voltage Noise C
BYP
=0.1µF, 10Hz to 100kHz 32 µV
RMS
LDO2 [V
EN
= 0V]
Variation from nominal V
OUT
–1 +1 % Output Voltage Accuracy
–40°C to +125°C –2 +2 %
Line Regulation V
IN
= V
OUT
+1V to 5.5V 0.02 0.3 %/V
Load Regulation
(6)
I
OUT
= 100µA to 30mA 0.2 0.5 %
Dropout Voltage
(7)
I
OUT
= 10mA; V
OUT
> 2.8V
I
OUT
= 30mA; V
OUT
> 2.8V
10
30
70 mV
mV
Ground Pin Current
(8)
I
OUT
= 0mA; EN1 = GND 190 300 µA
Ripple Rejection f = up to 1kHz; C
BYP
= 0.1µF
f = 1kHz – 20kHz; C
BYP
= 0.1µF
65
40
dB
dB
Current Limit V
OUT
= 0V 40 60 150 mA
Output Voltage Noise C
BYP
= 0.1µF, 10Hz to 100kHz 32 µV
RMS
Micrel, Inc. MIC2807
January 2007 5 M9999-013007-A
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. The maximum allowable power dissipation of any T
A
(ambient temperature) is P
D(max)
= (T
J(max)
- T
A
) / θ
JA
. Exceeding the maximum allowable power
dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.
4. Devices are ESD sensitive. Handling precautions recommended.
5. Specification for packaged product only.
6. Regulation is measured at constant junction temperature using low duty cycle pulse testing, changes in output voltage due to heating effects are
covered by the thermal regulation specification.
7. Dropout voltage is defined as the input-to-output differential at which the output voltage drops 2% below its nominal value measured at 1V differential.
8. Ground pin current is the regulator quiescent current.
Micrel, Inc. MIC2807
January 2007 6 M9999-013007-A
Typical Characteristics (DC/DC)
0
10
20
30
40
50
60
70
80
90
100
OUTPUT CURRENT (A)
1VOUT DC/DC Efficiency
0 0.1 0.2 0.3 0.4 0.5
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 3V
0
10
20
30
40
50
60
70
80
90
100
OUTPUT CURRENT (A)
1.2VOUT DC/DC Efficiency
0 0.1 0.2 0.3 0.4 0.5
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 3V
0
10
20
30
40
50
60
70
80
90
100
OUTPUT CURRENT (A)
1.5VOUT DC/DC Efficiency
0 0.1 0.2 0.3 0.4 0.5
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 3V
0
10
20
30
40
50
60
70
80
90
100
OUTPUT CURRENT (A)
1.8V
OUT
DC/DC Efficienc y
0 0.1 0.2 0.3 0.4 0.5
VIN = 4.2V
VIN = 3.6V
VIN = 3V
0
10
20
30
40
50
60
70
80
90
100
OUTPUT CURRENT (A)
2.5V
OUT
DC/DC Efficienc y
0 0.1 0.2 0.3 0.4 0.5
VIN = 4.2V
VIN = 3.6V
VIN = 3V
1.200
1.205
1.210
1.215
1.220
DC/DC Line Regu lation
INPUT VOLTAGE (V)
2.7 3.1 3.5 4.3 4.7 5.1 5.5
V
OUT
= 1.2V
I
OUT
= 100mA
V
DAC
= 0.4V
3.9
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
2.7
INPUT VOLTAGE (V)
DC/DC Sw itching Frequenc y
vs. Input Voltage
3.1 3.5 3.9 4.3 4.7 5.55.1
IOUT = 300mA
VOUT = 1.5V
VDAC = 0.5V
0.7
0.9
1.1
1.3
1.5
2.7
INPUT VOLTAGE (V)
DC/DC Current Limit
vs. Input Voltage
3.1 3.5 3.9 4.3 4.7 5.55.1
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5
DAC VOLTAGE (V)
DC/DC Output Voltage
vs. DAC Voltage
I
OUT
= 100mA
V
IN
= 4.2V
Bypass Mode
VOUT = VDAC x 3
1.815
1.817
1.819
1.821
1.823
1.825
DC/DC Load Reg ulation
VIN = 3.6V
0
OUTPUT CURRENT (A)
0.1 0.2 0.3 0.50.4
0.5
1.0
1.5
2.0
2.5
3.0
3.5
-40
TEMPERATURE (°C)
DC/DC Sw itching Frequenc y
vs. Temperature
-20 0 20 40 60 12010080
IOUT = 300mA
VOUT = 1.5V
VDAC = 0.5V
VIN = 3.6V
Micrel, Inc. MIC2807
January 2007 7 M9999-013007-A
Typical Characteristics ( LDO1/LDO2)
0
5
10
15
20
25
30
35
3 6 9 12151821242730
OUTPUT CURRENT (mA)
LDO2 D ropout Volt age
vs. Output Current
V
OUT
= 2.8V
2.800
2.802
2.804
2.806
2.808
0 5 10 15 20 25 30
OUTPUT CURRENT (mA)
LDO2 Load Regulation
VIN = 3.6V
COUT = 1µF
2.790
2.795
2.800
2.805
2.810
LDO2 Line Regulation
INPUT VOLTAGE (V)
2.7
IOUT = 15mA
COUT = 1µF
3.1 3.5 3.9 4.3 4.7 5.55.1
0
10
20
30
40
50
60
70
80
90
0.01 0.1 1 10 100 1000
FREQUENCY (kHz)
Power Supply Rejection
Ratio LDO2 [I
OUT
=20mA]
IOUT = 20mA
VOUT = 2.8V
VIN = 3.6V
COUT = 1µF
0
10
20
30
40
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
FREQUENCY (kHz)
Power Supply Rejection
Ratio LDO2 [IOUT=1mA]
I
OUT
= 1mA
V
OUT
= 2.8V
V
IN
= 3.6V
C
OUT
= 1µF
45
50
55
60
65
-40
TEMPERATURE (°C)
LDO1 Dropout Voltage
vs. Temperatu re
-20 0 20 40 60 12010080
IOUT = 150mA
VOUT = 2.8V
VIN = 3.6V
200
210
220
230
240
250
0 30 60 90 120 150
OUTPUT CURRENT (mA)
LDO1 Ground Current
vs. Output Current
VOUT = 2.8V
VIN = 3.6V
150
170
190
210
230
250
270
290
310
-40
TEMPERATURE (°C)
LDO1 Ground Current
vs. Temperatu re
-20 0 20 40 60 12010080
IOUT = 150mA
VOUT = 2.8V
VIN = 3.6V
2.76
2.77
2.78
2.79
2.80
2.81
LDO1 Line Regulation
INPUT VOLTAGE (V)
2.7 3.1 3.5 3.9 4.3 4.7 5.5
I
OUT
= 100mA
C
OUT
= 2.2µF
5.1
0
10
20
30
40
50
60
70
80
90
0.01 0.1 1 10 100 1000
FREQUENCY (kHz)
Power Supply Rejection
Ratio LDO1 [I
OUT
=5mA]
I
OUT
= 5mA
V
OUT
= 2.8V
V
IN
= 3.6V
C
OUT
= 2.2µF
0
10
20
30
40
50
60
70
90
100
0.1 1 10 100 1000
FREQUENCY (kHz)
Power Supply Rejection
Ratio LDO1 [I
OUT
=100mA]
COUT = 2.2µF
VOUT = 2.8V
VIN = 3.6V
80
10
20
30
40
50
60
70
80
5 45 85 125 165 205
OUTPUT CURRENT (mA)
LDO1 Dropout Voltage
vs. Output Current
VOUT = 2.8V
0
Micrel, Inc. MIC2807
January 2007 8 M9999-013007-A
Typical Characteristics (LDO1/LDO2 cont.)
0.001
0.01
0.1
1
10
0.01 0.1 1 10 100 1000
FREQUENCY (kHz)
LDO1/LDO2 Output Noise
Spectral De nsity
VOUT = 2.8V
VIN = 4.2V
COUT = 1µF
10000
Micrel, Inc. MIC2807
January 2007 9 M9999-013007-A
Functional Characteristics
DC/DC PWM Waveforms
Time (400ns/div)
V
IN
= 3.6V
V
OUT
= 1.8V
C
OUT
= 1µFI
OUT
= 100mA
L = 4.7µH
DC Coupled
(100mA/div)
Inductor Current
AC Coupled
(50mV/div)
Output Voltage
DC Coupled
(2V/div)
Switch Voltage
DC/DC Start-Up Waveforms
Time (10µs/div)
DC Coupled
(1V/div)
Outpu
t
Voltage
DC Coupled
(1V/div)
Enable Volta
g
e
I
OUT
= 300mA
V
IN
= 3.6V
V
OUT
= 1.8V
L = 4.7µH
C
OUT
= 1µF
DC/DC Load Transient
Time (20µs/div)
DC Coupled
(100mA/div)
Output Current
AC Coupled
(200mV/div)
Output Volta
g
e
L = 4.7µH
V
IN
= 3.6V
V
OUT
= 1.8V
C
OUT
= 1µF
300mA
10mA
Micrel, Inc. MIC2807
January 2007 10 M9999-013007-A
Functional Characteristics (cont.)
LDO1 Start-Up
W
aveforms
Time (10µs/div)
DC Coupled
(2V/div)
Output Volta
g
e
DC Coupled
(2V/div)
Enable Volta
g
e
I
OUT
= 200mA
V
IN
= 3.6V
V
OUT
= 2.8V
C
OUT
= 2.2µF
LDO1 Load Transient
Time (20µs/div)
DC Coupled
(200mV/div)
Output Current
AC Coupled
(50mV/div)
Output Volta
g
e
C
OUT
= 2.2µF
V
IN
= 3.6V
V
OUT
= 2.8V
200mA
10mA
Micrel, Inc. MIC2807
January 2007 11 M9999-013007-A
Functional Diagram
MIC2807 Block Diagram
Micrel, Inc. MIC2807
January 2007 12 M9999-013007-A
Device Functional Description
The MIC2807 is a power management IC with a single
integrated step-down regulator and two low dropout
regulators. LDO1 is a 200mA low dropout regulator and
LDO2 is a 30mA low dropout regulator. The 500mA
pulse-width-modulated (PWM) step-down regulator
utilizes a dynamically adjustable output voltage for
powering RF power amplifiers. By dynamically adjusting
the output power as necessary, battery life can be
dramatically improved in battery powered RF power
amplifier applications. Also where high power is
required, the step-down PWM regulator has a bypass
mode where an internal 95m switch shorts the OUT
and PVIN pins together.
Pin Functional Description
PVIN
PVIN (Power VIN) provides power to the MOSFETs for
the step-down switching regulator section of the
MIC2807, along with the current limit sensing circuitry.
Due to the high switching speeds, a minimum 1µF
capacitor is recommended close to PVIN and the power
ground (PGND) pin for bypassing*.
AVIN
AVIN (Analog VIN) provides power to the internal
reference and control section of the step-down regulator.
AVIN, VIN, and PVIN must all be tied together. Careful
layout should be considered to ensure high frequency
switching noise caused by PVIN is reduced before
reaching AVIN*.
DAC
The DAC pin is the control pin that sets the output
voltage of the step-down regulator. The Output voltage is
3X the voltage set on the DAC pin (V
OUT
= V
DAC
x 3).
When 1.2V or greater is applied to the DAC pin, the
MIC2807’s step-down regulator enters bypass mode. In
bypass mode, the input supply is connected to the
output through a 95m P-Channel MOSFET.
EN/EN1/EN2
The EN pin provides a logic level control of the step-
down regulator output. In the off state, supply current of
the device is greatly reduced (typically 1µA). Also, in
the off state, the output drive and bypass switch are
placed in a "tri-stated" condition, where both the high
side P-channel MOSFET and the low-side N-channel are
in an off or non-conducting state. EN1 provides logic
control for LDO1, and EN2 provides logic control for
LDO2. Placing a logic high voltage on any one of the
respective enable pins (EN, EN1 or EN2) will turn-on
(powering up the bias and control circuitry) that
respective regulator (DC/DC, LDO1 or LDO2). Do not
drive the enable pins above the supply voltage (AVIN
and VIN).
VIN
VIN provides power to the LDO1 and the LDO2 control
sections of the MIC2807. A minimum 1µF capacitor,
2.2µF recommended, should be placed as close as
possible between the VIN and AGND pins. VIN must
have the same voltage as AVIN*.
OUT
The OUT pin connects the internal bypass drain and the
feedback signal to the output. The bypass applies the
input voltage through a low resistance (95m typical) P-
Channel MOSFET switch. The feedback signal provides
the control path to set the output at 3 times the DAC
voltage.
SW
The SW pin connects directly to the inductor and
provides the switching current necessary to operate in
PWM mode. Due to the high speed switching on this pin,
the switch node should be routed away from sensitive
nodes.
PGND
PGND (Power GND) is the ground path for the
MOSFETs in the step-down regulator section. The
current loop for the power ground should be as small as
possible and separate from the analog ground (AGND)
loop*.
AGND
AGND (Analog GND) is the ground path for the biasing
and control circuitry. The current loop for the signal
ground should be separate from the Power ground
(PGND) loop*.
LDO1
Regulated output voltage of the LDO1. Power is
provided by VIN. Recommended output capacitance is
2.2µF.
LDO2
Regulated output voltage of the LDO2. Power is
provided by VIN. Recommended output capacitance is
1µF.
BYP
Filter capacitor for the voltage reference for the LDO1
and the LDO2. A 100nF capacitor is recommended from
the BYP pin to ground.
* Refer to PCB layout section of this data sheet for optimal layout
principles.
Micrel, Inc. MIC2807
January 2007 13 M9999-013007-A
Component Selection
Output Capacitor
LDO1 output requires a 2.2µF ceramic capacitor, while
the LDO2 and DC/DC regulator outputs require a 1µF
ceramic capacitor. All output capacitor values can be
increased to improve transient response, but perform-
ance has been optimized for a 2.2µF ceramic capacitor
for LDO1 and 1µF ceramic capacitors for both the
DC/DC regulator and LDO2. X7R/X5R dielectric-type
ceramic capacitors are recommended because of their
temperature performance. X5R/X7R-type capacitors
change capacitance by 15% over their operating
temperature range and are the most stable type of
ceramic capacitors. Z5U and Y5V dielectric capacitors
change value by as much as 50% to 60% respectively
over their operating temperature ranges.
Input Capacitor
For optimal bypassing a minimum 1µF ceramic, 2.2µF
recommended, should be placed as close as possible to
the VIN pin. X5R or X7R dielectrics are recommended
for the input capacitor. Y5V dielectrics lose most of their
capacitance over temperature and are therefore, not
recommended. For high frequency filtering a minimum
1µF is recommended close to the VIN and PGND pins.
Smaller case size capacitors are recommended due to
their lower ESR and ESL. Please refer to the PCB layout
section for an example of an appropriate circuit layout.
Inductor Selection
The MIC2807 is designed for use with a 4.7µH inductor.
Proper selection should ensure that the inductor can
handle the maximum average and peak currents
required by the load. Maximum current ratings of the
inductor are generally given in two methods; permissible
DC current and saturation current. Permissible DC
current can be rated either for a 40°C temperature rise
or a 10% to 20% loss in inductance. Ensure that the
inductor selected can handle the maximum operating
current. When saturation current is specified, make sure
that there is enough margin, so that the peak current will
not saturate the inductor. Peak inductor current can be
calculated as follows:
Lf2
V
V
1V
II IN
OUT
OUT
OUTPK ××
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−
+=
IPK: Peak Inductor Current
IOUT: Output/Load Current
VIN: Input Voltage
VOUT: Output Voltage
f: Switching Frequency of PWM Regulator
L: Inductor Value
Micrel, Inc. MIC2807
January 2007 14 M9999-013007-A
PCB Layout
Layout Schematic
Micrel, Inc. MIC2807
January 2007 15 M9999-013007-A
Top Layer
Micrel, Inc. MIC2807
January 2007 16 M9999-013007-A
Bottom Layer
Micrel, Inc. MIC2807
January 2007 17 M9999-013007-A
Package Information
17-Pin 2.5mm x 2.8mm MLF
®
(ML)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2006 Micrel, Incorporated.
