MICREL MIC2808

MIC2808
RF PA Power Management IC
2MHz, 600mA DC/DC w/DAC Input and
Bypass Switch, Dual Low Noise
200mA/30mA LDO Regulators
General Description
Features
The MIC2808 integrates a high performance 600mA
DC/DC step down regulator 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 MIC2808
improves efficiency in the handset without compromising
quality.
The MIC2808 has a 2MHz, constant frequency pulse width
modulated (PWM) DC/DC regulator designed for low noise
operation and high efficiency. The output voltage (VOUT) is
variable from 0.3V to the input voltage (VIN), adjustable
from 0.3V to 3.6V through a DAC input when VIN > VOUT.
The regulator 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 regulator has a
bypass mode of operation where the input voltage node
(PVIN pin) is shorted to the output voltage node (OUT pin)
through a 95mΩ 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 regulator along with dual
low noise LDO regulators enables a very quiet and
efficient solution for mobile applications.
The MIC2808 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 2.0mm x 2.5mm TMLF package.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
•
•
•
•
•
2.7V to 5.5V input voltage range
Stable with ceramic output capacitors
Tiny 16-pin 2.0mm x 2.5mm TMLF® Package
Thermal shutdown protection
Current limit protection
RF PA Power Supply DC/DC Regulator
• Adjustable output power supply – DAC controlled
– VOUT = VDAC x 3
• Bypass mode operation
– Internal 95mΩ switch between PVIN and OUT pins
– VDAC > 1.2V
• Up to 600mA 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
WiMAX/Wibro modules
WiFi modules
Power amplifier modules (PAMs) with linear PAs
Typical Application
4.5
DC/DC Output Voltage
vs. DAC Voltage
x
3
3.0
V
D
AC
2.5
T
O
U
V
1.5
=
2.0
Bypass Mode
VIN = 4.2V
4.0 IOUT = 100mA
3.5
1.0
0.5
CDMA2000/WCDMA RF Power Supply Circuit
0
0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5
DAC VOLTAGE (V)
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
July 2009
M9999-071709-A
Micrel, Inc.
MIC2808
Ordering Information
Marking
Code
Part Number
MIC2808-NNYFT
NNYJ
LDO1/LDO2
Voltage(3)
Junction
Temp. Range
2.85V/2.85V
–40°C to +125°C
Package(1)
16-Pin 2.0mm x 2.5mm Thin MLF
Lead Finish(2)
®
Pb-Free
Note:
®
1. Thin MLF
= Pin 1 identifier.
®
2. Thin MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is halogen free.
3. Contact Micrel for other output voltages.
OUT
OUT
LDO2
Pin Configuration
LDO1
PGND
PVIN
BYP
EN1
DAC
AVIN
EN
EN2
NC
SW
AGND
VIN
16-Pin 2.0mm x 2.5mm Thin MLF® (FT)
(Top View)
July 2009
2
M9999-071709-A
Micrel, Inc.
MIC2808
Pin Description
Pin
Number
Pin Name
1
LDO1
2
VIN
LDO1 and LDO2 Supply Voltage. Must be connected to PIN 9 (AVIN).
3
EN2
Enables the LDO2 regulator. Do not leave floating.
4
BYP
Filter capacitor for LDO1 and LDO2 internal voltage reference. Connect a 0.1µF capacitor-to-ground.
5
DAC
DAC Control Input (Analog Voltage Input). Provides control of output voltage of DC/DC regulator. The
output voltage is 3x’s the DAC voltage (Ex. 0.5VDAC = 1.5VOUT) when VIN > VOUT. Bypass mode is enabled
when the DAC voltage exceeds 1.2V or VIN ≤ VOUT.
6
AGND
7
NC
8
EN
9
AVIN
Pin Function
Output of the LDO1.
Signal ground.
No Connect.
Enables the DC/DC Regulator. Do not leave floating.
Supply voltage for DC/DC regulator control circuitry and reference voltage circuit. Must be connected to PIN
2 (VIN).
10
EN1
Enables LDO1 Regulator. Do not leave floating.
11
PVIN
Supply Voltage: Requires bypass capacitor to ground.
12
SW
Switch: Internal power MOSFET output switches of DC/DC regulator.
13
PGND
14, 15
OUT
Drain of internal bypass switch, also serves as feedback for the internal regulator.
16
LDO2
Output of the LDO2.
July 2009
Power ground.
3
M9999-071709-A
Micrel, Inc.
MIC2808
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (PVIN, AVIN, VIN) ............................ 0V to 6V
Output Switch Voltage (VSW). ...........................................6V
DAC Input Voltage (VDAC)....................................... 0V to VIN
Logic Input Voltage (VEN, VEN1, VEN2) ..................... 0V to VIN
Power Dissipation(3)...................................Internally Limited
Storage Temperature (Ts) .........................–65°C to +150°C
ESD Rating(4) ................................................................ ±2kV
Supply Voltage (PVIN, AVIN, VIN) ...................... 2.7V to 5.5V
Output Voltage (VOUT) ............................................ 0V to VIN
Enable Voltage (VEN, VEN1, VEN2)............................ 0V to VIN
DAC Input Voltage (VDAC).................................... 0.1V to VIN
Junction Temperature (TJ) ........................ –40°C to +125°C
Thermal Resistance
2.0mmx2.5mm TMLF-16 (θJA)...........................96°C/W
Electrical Characteristics(5)
DC/DC Regulator
VIN = PVIN = AVIN = VEN = 3.6V; VDAC = 0.6V; VEN1 = VEN2 = 0V; L = 4.7µH; COUT = 1µF; TA = 25°C, bold values indicate
–40°C< TJ < +125°C, unless noted.
LDO1/LDO2
VIN = VEN1 = VEN2 = 3.6V; COUTLDO1 = 2.2µF; VEN = 0V; COUTLDO2 = 1µF; IOUT = 100µA; TA = 25°C, bold values indicate
–40°C< TJ < +125°C, unless noted.
Parameter
Supply Voltage Range
Total Quiescent Current
Enable Pin Threshold
Condition
Min
2.7
VEN = VEN1 = VEN2 = 3.6V
VDAC = 0.6V (DC/DC: not switching)
Logic Low
Logic High
(turn-on)
V
µA
70
0.01
1
V
V
mV
µA
2.6
2.7
V
85
160
20
mV
ºC
ºC
1
5
µA
490
650
µA
360
1.8
0.05
450
1.854
µA
V
%/V
100
VDAC = 1.3V
VDAC = 0.6V (regulator on, not switching)
VDAC = 0.6V, ILOAD = 0mA
3.0V< VIN < 4.5, ILOAD = 10mA
1.746
%
0.5
0mA < IOUT < 400mA
0.2
ISW = -100mA, High-Side Switch
ISW = 100mA, Low-Side Switch
0.65
0.55
0.59
0.85
0.7
0.8
1.6
Ω
Ω
A
1.8
2
2.2
MHz
Current Limit
(Peak SW Current)
Frequency
July 2009
5.5
0.4
Maximum Duty Cycle
Output Voltage
Line Regulation
Output Voltage
Load Regulation
Switch On-Resistance
Units
1.3
Shutdown Temperature
Hysteresis
Total Shutdown Current
VEN = VEN1 = VEN2 = 0V
DC/DC Regulator [VEN1 = VEN2 = 0V]
Bypass Quiescent
Current
Quiescent Current
Output Voltage
Max
480
Enable Pin Hysteresis
Enable Pin Input Current
Under-Voltage
Lockout Threshold
UVLO Hysteresis
Shutdown Temperature
Typ
4
%
M9999-071709-A
Micrel, Inc.
MIC2808
Parameter
Condition
Turn-On Time
DAC Input Current
Output Voltage/
DAC Voltage
Bypass Switch
Threshold
Bypass Switch
Hysteresis
Bypass Transition Time
Bypass Switch
On-Resistance
Bypass Switch Leakage
Min
Typ
Max
Units
IOUT = 100µA
25
0.15
50
2
µs
µA
(internally set)
3
DAC Voltage required to enable bypass mode
Line Regulation
Load Regulation(6)
Dropout Voltage(7)
Ground Pin Current(8)
Ripple Rejection
Current Limit
Output Voltage Noise
LDO2 [VEN = 0V]
Output Voltage Accuracy
Line Regulation
Load Regulation(6)
Dropout Voltage(7)
Ground Pin Current(8)
Ripple Rejection
Current Limit
Output Voltage Noise
July 2009
1.2
1.224
35
Delay from VDAC = 1.3V to VOUT = 0.90VIN
VIN = 3.0V, IBYPASS = 100mA
Bypass Over-Current
Limit
Current Limit Retry Time
Current Limit Retry
Duty Cycle
LDO1/LDO2 [VEN = 0V]
Total Ground Current(8)
Turn-on Time
LDO1 [VEN = 0V]
Output Voltage Accuracy
1.176
V/V
10
95
1
VEN1 = VEN2 = 3.6V
LDO1 or LDO2; CBYP = 0.1µF
1.4
Variation from nominal VOUT
–40°C to +125°C
VIN = VOUT +1V to 5.5V
IOUT = 100µA to 30mA
IOUT = 10mA; VOUT > 2.8V
IOUT = 30mA; VOUT > 2.8V
IOUT = 0mA; EN1 = GND
f = up to 1kHz; CBYP = 0.1µF
f = 1kHz – 20kHz; CBYP = 0.1µF
VOUT = 0V
CBYP = 0.1µF, 10Hz to 100kHz
5
µs
mΩ
5
µA
2.5
A
40
12.5
%
0.02
0.2
20
55
70
190
70
45
300
32
–1
–2
40
150
µs
–1
–2
225
mV
32
220
30
Variation from nominal VOUT
–40°C to +125°C
VIN = VOUT +1V to 5.5V
IOUT = 100µA to 200mA
IOUT = 50mA; VOUT > 2.8V
IOUT = 150mA; VOUT > 2.8V
IOUT = 200mA; VOUT > 2.8V
IOUT = 0mA; EN2 = GND
f = up to 1kHz; CBYP = 0.1µF
f = 1kHz – 20kHz; CBYP = 0.1µF
VOUT = 0V
CBYP=0.1µF, 10Hz to 100kHz
V
0.02
0.2
10
30
190
65
40
60
32
100
+1
+2
0.3
0.5
100
300
700
+1
+2
0.3
0.5
60
300
150
µA
µs
%
%
%/V
%
mV
mV
mV
µA
dB
dB
mA
µVRMS
%
%
%/V
%
mV
mV
µA
dB
dB
mA
µVRMS
M9999-071709-A
Micrel, Inc.
MIC2808
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 TA (ambient temperature) is PD(max) = (TJ(max) - TA) / θJA. 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.
July 2009
6
M9999-071709-A
Micrel, Inc.
MIC2808
Typical Characteristics (DC/DC)
1.2V OUT DC/DC Efficiency
100
90
100
90
80
80
VIN = 4.2V
VIN = 3.6V
VIN = 3V
70
60
50
40
20
10
20
10
0.1
0.2
0.3
0.4
OUTPUT CURRENT (A)
0.5
100
90
60
50
0.1
0.2
0.3
0.4
OUTPUT CURRENT (A)
0.5
80
70
VIN = 4.2V
VIN = 3.6V
VIN = 3V
60
50
60
50
40
30
40
30
20
20
10
0
0
10
0
0
0.1
0.2
0.3
0.4
OUTPUT CURRENT (A)
0.5
DC/DC Switching Frequency
vs. Input Voltage
2.8
1.5
0.1
0.2
0.3
0.4
OUTPUT CURRENT (A)
VIN = 4.2V
VIN = 3.6V
VIN = 3V
DC/DC Line Regulation
1.215
1.210
1.205
0.1
0.2
0.3
0.4
OUTPUT CURRENT (A)
0.5
DC/DC Current Limit
vs. Input Voltage
1.3
VOUT = 1.2V
IOUT = 100mA
VDAC = 0.4V
1.200
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
INPUT VOLTAGE (V)
DC/DC Output Voltage
vs. DAC Voltage
4.5
VIN = 4.2V
4.0 IOUT = 100mA
3.5
VDAC = 0.5V
VOUT = 1.5V
IOUT = 300mA
1.6
x
D
V
T
U
O
V
0.9
=
2.0
1.5
1.8
AC
2.5
1.1
2.0
3
3.0
2.2
0.5
1.220
2.6
2.4
10
0
0
2.5V OUT DC/DC Efficiency
100
90
80
70
VIN = 4.2V
VIN = 3.6V
VIN = 3V
40
30
20
0
0
1.8V OUT DC/DC Efficiency
90
80
70
VIN = 4.2V
VIN = 3.6V
VIN = 3V
50
40
30
0
0
100
70
60
30
1.5V OUT DC/DC Efficiency
Bypass Mode
1V OUT DC/DC Efficiency
1.0
0.5
1.4
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
INPUT VOLTAGE (V)
0.7
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
INPUT VOLTAGE (V)
DC/DC Load Regulation
DC/DC Switching Frequency
vs. Temperature
0
0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5
DAC VOLTAGE (V)
3.5
1.825
3.0
1.823
2.5
1.821
2.0
1.819
1.5
1.817
1.815
0
July 2009
VIN = 3.6V
VDAC = 0.5V
VOUT = 1.5V
IOUT = 300mA
1.0
VIN = 3.6V
0.1
0.2
0.3
0.4
OUTPUT CURRENT (A)
0.5
0.5
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
7
M9999-071709-A
Micrel, Inc.
MIC2808
Typical Characteristics (LDO1/LDO2)
LDO2 Dropout Voltage
vs. Output Current
35
LDO2 Line Regulation
LDO2 Load Regulation
2.854
2.860
2.852
2.855
2.850
2.850
30
25
20
15
10
2.848
5
VOUT = 2.85V
0
36
90
2.845
VIN = 3.6V
COUT = 1µF
91 21 51 82 12 42 73 0
OUTPUT CURRENT (mA)
Power Supply Rejection
Ratio LDO2 [I OUT =20mA]
80
70
60
50
40
30
VIN = 3.6V
20 VOUT = 2.85V
I
= 20mA
10 OUT
COUT = 1µF
0
0.01 0.1
11
0
100
FREQUENCY (kHz)
1000
LDO1 Ground Current
vs. Output Current
250
2.846
05
100
90
10 15 20 25 30
OUTPUT CURRENT (mA)
Power Supply Rejection
Ratio LDO2 [I OUT =1mA]
80
70
60
50
40
30 VIN = 3.6V
20 VOUT = 2.85V
I
= 1mA
10 COUT = 1µF
OUT
0
0.01 0.1
11
0
100
FREQUENCY (kHz)
310
IOUT = 15mA
COUT = 1µF
2.840
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
INPUT VOLTAGE (V)
65
LDO1 Dropout Voltage
vs. Temperature
60
55
50
1000
LDO1 Ground Current
vs. Temperature
VOUT = 2.85V
IOUT = 150mA
45
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
LDO1 Line Regulation
2.86
290
240
2.85
270
250
230
2.84
230
220
190
210
200
03
90
2.83
210
VIN = 3.6V
VOUT = 2.85V
06
09
0
120 150
OUTPUT CURRENT (mA)
Power Supply Rejection
Ratio LDO1 [I OUT =5mA]
150
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
100
80
90
70
80
60
70
50
40
30
VIN = 3.6V
20 VOUT = 2.85V
IOUT = 5mA
10
COUT = 2.2µF
0
0.01 0.1
11
0
100
FREQUENCY (kHz)
July 2009
VIN = 3.6V
VOUT = 2.85V
IOUT = 150mA
170
Power Supply Rejection
Ratio LDO1 [I OUT =100mA]
IOUT = 100mA
COUT = 2.2µF
2.81
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
INPUT VOLTAGE (V)
80
LDO1 Dropout Voltage
vs. Output Current
70
60
60
50
50
40
40
30
30
1000
2.82
20 VIN = 3.6V
= 2.85V
V
10 COUT = 2.2µF
OUT
0
0.1
1
10
100
FREQUENCY (kHz)
8
20
10
1000
0
5
VOUT = 2.85V
45
85
125 165 205
OUTPUT CURRENT (mA)
M9999-071709-A
Micrel, Inc.
MIC2808
Typical Characteristics (LDO1/LDO2 cont.)
10
LDO1/LDO2 Output Noise
Spectral Density
1
0.1
0.01
VIN = 4.2V
VOUT = 2.85V
COUT = 1µF
0.001
0.01 0.1
July 2009
1
10 100 1000 10000
FREQUENCY (kHz)
9
M9999-071709-A
Micrel, Inc.
MIC2808
Functional Characteristics
DC/DC PWM Waveforms
VIN = 3.6V
IOUT = 100mA
VOUT = 1.8V
L = 4.7µH
VIN = 3.6V
Output Voltag e
DC Coupled
(1V/div)
Inductor Current
DC Coupled
(100mA/div)
Output Voltage
AC Coupled
(10mV/div)
Enable Voltag e
DC Coupled
(1V/div)
Switch Voltage
DC Coupled
(2V/div)
DC/DC Start-Up Waveforms
COUT = 1µF
VOUT = 1.8V
IOUT = 300mA
L = 4.7µH
COUT = 1µF
Time (10µs/div )
Time (400ns/div)
Output Voltag e
AC Coupled
(200mV/div)
DC/DC Load Transient
300mA
VIN = 3.6V
Output Current
DC Coupled
(100mA/div)
VOUT = 1.8V
L = 4.7µH
COUT = 1µF
10mA
Time (20µs/div )
July 2009
10
M9999-071709-A
Micrel, Inc.
MIC2808
Functional Characteristics (continued)
LDO1 Load Transient
Enable Voltage
DC Coupled
(2V/div)
Output Voltage
AC Coupled
(50mV/div)
LDO1 Start-Up Waveforms
Output Current
DC Coupled
(200mV/div)
Output Voltage
DC Coupled
(2V/div)
200mA
VIN = 3.6V
VOUT = 2.85V
IOUT = 200mA
COUT = 2.2µF
VIN = 3.6V
VOUT = 2.85V
COUT = 2.2µF
Time (10µs/div)
July 2009
10mA
Time (20µs/div)
11
M9999-071709-A
Micrel, Inc.
MIC2808
Functional Diagram
MIC2808 Block Diagram
July 2009
12
M9999-071709-A
Micrel, Inc.
MIC2808
VIN
VIN provides power to the LDO1 and the LDO2 control
sections of the MIC2808. 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*.
Device Functional Description
The MIC2808 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 95mΩ switch connects the OUT
and PVIN pins together.
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 (95mΩ typical) PChannel MOSFET switch. The feedback signal provides
the control path to set the output at three 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.
Pin Functional Description
PVIN
PVIN (Power VIN) provides power to the MOSFETs for
the step-down switching regulator section of the
MIC2808, 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*.
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*.
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*.
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*.
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 (VOUT = VDAC x 3).
When 1.2V or greater is applied to the DAC pin, the
MIC2808’s step-down regulator enters bypass mode. In
bypass mode, the input supply is connected to the
output through a 95mΩ P-Channel MOSFET.
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.
EN/EN1/EN2
The EN pin provides a logic level control of the stepdown 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).
July 2009
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.
13
M9999-071709-A
Micrel, Inc.
MIC2808
Inductor Selection
The MIC2808 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:
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 performance 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.
IPK = IOUT
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.
July 2009
IPK:
IOUT:
VIN:
VOUT:
f:
L:
14
⎛
⎞
V
VOUT ⎜⎜1 − OUT ⎟⎟
VIN ⎠
⎝
+
2× f ×L
Peak Inductor Current
Output/Load Current
Input Voltage
Output Voltage
Switching Frequency of PWM Regulator
Inductor Value
M9999-071709-A
Micrel, Inc.
MIC2808
Typical Application Circuit
LDO2
GND
C3
1µF
6.3V
OUT
LDO2
OUT
VIN
VIN
VIN
GND
EN2
DAC
PVIN
C8
2.2µF
6.3V
AVIN
C6
1µF
6.3V
VIN
EN2
C2
1µF
6.3V
VOUT
SW
C1
2.2µF
6.3V
LDO1
L1
4.7µH/1A
LDO1
MIC2808-xxYFT
BYP
C4
0.1µF
6.3V
C7
1µF
6.3V
EN
EN
EN1
EN1
DAC
C5
1µF
6.3V
NC
AGND
PGND
Bill of Materials
Item
Part Number
Manufacturer
(1)
Description
Qty.
C1, C8
C1608X5R0J225K
TDK
2.2µF Ceramic Capacitor, 6.3V, X5R, Size 0603
2
C2,
C3,
C5-C7
C1608X5R0J105K
TDK(1)
1µF Ceramic Capacitor, 6.3V, X5R, Size 0603
5
C4
C1608X5R0J104K
TDK(1)
0.1µF Ceramic Capacitor, 6.3V, X5R, Size 0603
1
VLS3012T-4R7M1R0
L1
4.7µH, 1.2A, 130mΩ, L3.0mm x W3.0mm x H1.2mm
(3)
CDH3D13-4R7NC
Sumida
ME3220-472MLB
Coilcraft(4)
LQH32CN4R7M53
MIPF2520D4R7
U1
TDK
(1)
MIC2808-xxYFT
(5)
Murata
FDK
(6)
Micrel, Inc.(7)
4.7µH, 1.15A, 175mΩ, L3.0mm x W3.0mm x H1.4mm
1
4.7µH, 1.4A, 190mΩ, L3.2mm x W2.5mm x H2.0mm
4.7µH, 650mA, 150mΩ, L3.2mm x W2.5mm x H1.55mm
4.7µH, 1.1A, 110mΩ, L2.5mm x W2.0mm x H1.0mm
2MHz 600mA Buck with DAC Input, Bypass Switch and Dual
Low Noise 200mA/30mA LDOs
1
Notes:
1. TDK: www.tdk.com
2. Vishay: www.vishay.com
3. Sumida: www.sumida.com
4. Coilcraft: www.coilcraft.com
5. Murata: www.murata.com
6. FDK: www.fdk.co.jp
7. Micrel, Inc.: www.micrel.com
July 2009
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M9999-071709-A
Micrel, Inc.
MIC2808
Top Layer
July 2009
16
M9999-071709-A
Micrel, Inc.
MIC2808
Bottom Layer
July 2009
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M9999-071709-A
Micrel, Inc.
MIC2808
Package Information
®
16-Pin 2.0mm x 2.5mm FC-TMLF (FT)
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.
© 2009 Micrel, Incorporated.
July 2009
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M9999-071709-A