MIC2808-NNYFT [MICREL]
RF PA Power Management IC 2MHz, 600mA DC/DC w/DAC Input and Bypass Switch, Dual Low Noise 200mA/30mA LDO Regulators; RF PA电源管理IC为2MHz , 600毫安DC / DC W / DAC输入和旁路开关,双路低噪声200毫安/ 30毫安LDO稳压器型号: | MIC2808-NNYFT |
厂家: | MICREL SEMICONDUCTOR |
描述: | RF PA Power Management IC 2MHz, 600mA DC/DC w/DAC Input and Bypass Switch, Dual Low Noise 200mA/30mA LDO Regulators |
文件: | 总18页 (文件大小:486K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
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.
• 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
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
–
VOUT = VDAC x 3
• Bypass mode operation
–
–
Internal 95mꢀ switch between PVIN and OUT pins
VDAC > 1.2V
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.
• 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
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.
Applications
• CDMA2000 mobile phones
• UMTS/WCDMA mobile phones
• WiMAX/Wibro modules
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
• WiFi modules
• Power amplifier modules (PAMs) with linear PAs
Typical Application
DC/DC Output Voltage
vs. DAC Voltage
4.5
V
OUT
= 4.2V
= 100mA
IN
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
I
0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5
DAC VOLTAGE (V)
CDMA2000/WCDMA RF Power Supply Circuit
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
M9999-071709-A
July 2009
Micrel, Inc.
MIC2808
Ordering Information
Part Number
Marking
Code
LDO1/LDO2
Voltage(3)
Junction
Temp. Range
Package(1)
Lead Finish(2)
MIC2808-NNYFT
NNYJ
2.85V/2.85V
–40°C to +125°C
16-Pin 2.0mm x 2.5mm Thin MLF®
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.
Pin Configuration
LDO1
VIN
PGND
SW
EN2
BYP
DAC
PVIN
EN1
AVIN
16-Pin 2.0mm x 2.5mm Thin MLF® (FT)
(Top View)
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MIC2808
Pin Description
Pin
Number
Pin Name Pin Function
1
2
3
4
5
LDO1
VIN
Output of the LDO1.
LDO1 and LDO2 Supply Voltage. Must be connected to PIN 9 (AVIN).
Enables the LDO2 regulator. Do not leave floating.
EN2
BYP
DAC
Filter capacitor for LDO1 and LDO2 internal voltage reference. Connect a 0.1µF capacitor-to-ground.
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
7
8
9
AGND
NC
Signal ground.
No Connect.
EN
Enables the DC/DC Regulator. Do not leave floating.
AVIN
Supply voltage for DC/DC regulator control circuitry and reference voltage circuit. Must be connected to PIN
2 (VIN).
10
11
EN1
PVIN
SW
Enables LDO1 Regulator. Do not leave floating.
Supply Voltage: Requires bypass capacitor to ground.
Switch: Internal power MOSFET output switches of DC/DC regulator.
Power ground.
12
13
PGND
OUT
14, 15
16
Drain of internal bypass switch, also serves as feedback for the internal regulator.
Output of the LDO2.
LDO2
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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
Condition
Min
2.7
Typ
Max
5.5
Units
Supply Voltage Range
Total Quiescent Current
V
VEN = VEN1 = VEN2 = 3.6V
VDAC = 0.6V (DC/DC: not switching)
480
µA
Enable Pin Threshold
Logic Low
Logic High
0.4
V
V
1.3
Enable Pin Hysteresis
70
0.01
2.6
mV
µA
V
Enable Pin Input Current
1
Under-Voltage
(turn-on)
2.7
Lockout Threshold
UVLO Hysteresis
85
160
20
mV
ºC
Shutdown Temperature
Shutdown Temperature
Hysteresis
ºC
Total Shutdown Current
VEN = VEN1 = VEN2 = 0V
1
5
µA
DC/DC Regulator [VEN1 = VEN2 = 0V]
Maximum Duty Cycle
100
%
Bypass Quiescent
Current
VDAC = 1.3V
490
650
µA
Quiescent Current
Output Voltage
VDAC = 0.6V (regulator on, not switching)
VDAC = 0.6V, ILOAD = 0mA
360
1.8
450
1.854
0.5
µA
V
1.746
Output Voltage
Line Regulation
3.0V< VIN < 4.5, ILOAD = 10mA
0.05
%/V
Output Voltage
Load Regulation
0mA < IOUT < 400mA
0.2
%
Switch On-Resistance
ISW = -100mA, High-Side Switch
0.55
0.59
0.85
0.7
0.8
1.6
ꢀ
ꢀ
A
I
SW = 100mA, Low-Side Switch
Current Limit
0.65
(Peak SW Current)
Frequency
1.8
2
2.2
MHz
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MIC2808
Parameter
Condition
Min
Typ
25
Max
50
2
Units
µs
Turn-On Time
DAC Input Current
IOUT = 100µA
0.15
3
µA
Output Voltage/
DAC Voltage
(internally set)
V/V
Bypass Switch
Threshold
DAC Voltage required to enable bypass mode
1.176
1.2
35
1.224
V
Bypass Switch
Hysteresis
mV
Bypass Transition Time
Delay from VDAC = 1.3V to VOUT = 0.90VIN
VIN = 3.0V, IBYPASS = 100mA
10
95
40
µs
Bypass Switch
On-Resistance
150
mꢀ
Bypass Switch Leakage
5
µA
A
Bypass Over-Current
Limit
1
1.4
2.5
Current Limit Retry Time
32
µs
%
Current Limit Retry
Duty Cycle
12.5
LDO1/LDO2 [VEN = 0V]
Total Ground Current(8)
Turn-on Time
VEN1 = VEN2 = 3.6V
220
30
µA
µs
LDO1 or LDO2; CBYP = 0.1µF
100
LDO1 [VEN = 0V]
Output Voltage Accuracy Variation from nominal VOUT
–40°C to +125°C
–1
+1
+2
%
%
–2
Line Regulation
VIN = VOUT +1V to 5.5V
IOUT = 100µA to 200mA
IOUT = 50mA; VOUT > 2.8V
0.02
0.2
20
0.3
0.5
%/V
%
Load Regulation(6)
Dropout Voltage(7)
mV
mV
mV
µA
I
I
OUT = 150mA; VOUT > 2.8V
OUT = 200mA; VOUT > 2.8V
55
70
100
300
Ground Pin Current(8)
Ripple Rejection
IOUT = 0mA; EN2 = GND
f = up to 1kHz; CBYP = 0.1µF
f = 1kHz – 20kHz; CBYP = 0.1µF
VOUT = 0V
190
70
dB
45
dB
Current Limit
225
300
32
700
mA
µVRMS
Output Voltage Noise
LDO2 [VEN = 0V]
CBYP=0.1µF, 10Hz to 100kHz
Output Voltage Accuracy Variation from nominal VOUT
–40°C to +125°C
–1
+1
+2
%
%
–2
Line Regulation
VIN = VOUT +1V to 5.5V
IOUT = 100µA to 30mA
IOUT = 10mA; VOUT > 2.8V
0.02
0.2
10
0.3
0.5
%/V
%
Load Regulation(6)
Dropout Voltage(7)
mV
mV
µA
I
OUT = 30mA; VOUT > 2.8V
30
60
Ground Pin Current(8)
Ripple Rejection
IOUT = 0mA; EN1 = GND
f = up to 1kHz; CBYP = 0.1µF
f = 1kHz – 20kHz; CBYP = 0.1µF
VOUT = 0V
190
65
300
dB
40
dB
Current Limit
40
60
150
mA
µVRMS
Output Voltage Noise
CBYP = 0.1µF, 10Hz to 100kHz
32
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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.
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Micrel, Inc.
MIC2808
Typical Characteristics (DC/DC)
1V
DC/DC Efficiency
1.2V
DC/DC Efficiency
OUT
1.5V
DC/DC Efficiency
OUT
OUT
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
V
V
V
= 4.2V
= 3.6V
= 3V
IN
IN
IN
V
V
V
= 4.2V
= 3.6V
= 3V
IN
IN
IN
V
= 4.2V
= 3.6V
= 3V
IN
V
IN
V
IN
0
0.1
0.2
0.3
0.4
0.5
0
0.1
0.2
0.3
0.4
0.5
0
0.1
0.2
0.3
0.4
0.5
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
1.8V
DC/DC Efficiency
2.5V
DC/DC Efficiency
OUT
DC/DC Line Regulation
OUT
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
1.220
1.215
1.210
1.205
1.200
V
V
V
= 4.2V
= 3.6V
= 3V
IN
IN
IN
V
V
V
= 4.2V
= 3.6V
= 3V
IN
IN
IN
V
OUT
V
= 1.2V
OUT
I
= 100mA
= 0.4V
DAC
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
INPUT VOLTAGE (V)
0
0.1
0.2
0.3
0.4
0.5
0
0.1
0.2
0.3
0.4
0.5
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
DC/DC Switching Frequency
vs. Input Voltage
DC/DC Current Limit
vs. Input Voltage
DC/DC Output Voltage
vs. DAC Voltage
2.8
1.5
1.3
1.1
0.9
0.7
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
OUT
= 4.2V
IN
I
= 100mA
2.6
2.4
2.2
2.0
1.8
1.6
1.4
V
V
OUT
= 0.5V
= 1.5V
DAC
OUT
I
= 300mA
0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5
DAC VOLTAGE (V)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
INPUT VOLTAGE (V)
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
1.825
3.5
3.0
2.5
2.0
1.5
1.0
0.5
1.823
1.821
1.819
1.817
1.815
V
V
V
= 3.6V
IN
= 0.5V
= 1.5V
DAC
OUT
V
IN
= 3.6V
I
= 300mA
OUT
0
0.1
0.2
0.3
0.4
0.5
-40 -20
0
20 40 60 80 100 120
OUTPUT CURRENT (A)
TEMPERATURE (°C)
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Micrel, Inc.
MIC2808
Typical Characteristics (LDO1/LDO2)
LDO2 Dropout Voltage
vs. Output Current
LDO2 Line Regulation
LDO2 Load Regulation
35
30
25
20
15
10
5
2.854
2.852
2.850
2.848
2.846
2.860
2.855
2.850
2.845
2.840
V
IN
= 3.6V
I
= 15mA
C = 1µF
OUT
OUT
V
OUT
= 2.85V
C
OUT
= 1µF
0
05
10 15 20 25 30
OUTPUT CURRENT (mA)
36
91 21 51 82 12 42 73 0
OUTPUT CURRENT (mA)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
INPUT VOLTAGE (V)
Power Supply Rejection
LDO1 Dropout Voltage
vs. Temperature
Power Supply Rejection
Ratio LDO2 [I
=1mA]
OUT
Ratio LDO2 [I
=20mA]
OUT
100
90
80
70
60
50
40
30
20
10
0
65
90
80
70
60
50
40
30
20
10
0
60
55
50
45
V
V
OUT
C
= 3.6V
IN
OUT
V
V
I
= 3.6V
IN
OUT
= 2.85V
= 20mA
= 2.85V
I
= 1mA
= 1µF
V
I
= 2.85V
OUT
OUT
= 1µF
OUT
C
= 150mA
OUT
OUT
0.01 0.1
11
0
100 1000
0.01 0.1
11
0
100 1000
-40 -20
0
20 40 60 80 100 120
FREQUENCY (kHz)
FREQUENCY (kHz)
TEMPERATURE (°C)
LDO1 Ground Current
vs. Output Current
LDO1 Ground Current
vs. Temperature
LDO1 Line Regulation
250
240
230
220
210
200
310
290
270
250
230
210
190
170
150
2.86
2.85
2.84
2.83
2.82
2.81
V
V
I
= 3.6V
IN
OUT
I
= 100mA
OUT
= 2.85V
= 150mA
OUT
C
V
V
= 3.6V
IN
OUT
= 2.2µF
= 2.85V
OUT
03
06
09
0
120 150
-40 -20
0
20 40 60 80 100 120
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
TEMPERATURE (°C)
Power Supply Rejection
Power Supply Rejection
Ratio LDO1 [I =100mA]
LDO1 Dropout Voltage
vs. Output Current
Ratio LDO1 [I
=5mA]
OUT
OUT
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
V
V
I
= 3.6V
IN
OUT
= 2.85V
V
V
= 3.6V
IN
OUT
= 5mA
= 2.2µF
= 2.85V
= 2.2µF
OUT
C
V
OUT
= 2.85V
C
OUT
OUT
0.01 0.1
11
0
100 1000
0.1
1
10
100
1000
5
45
85
125 165 205
FREQUENCY (kHz)
FREQUENCY (kHz)
OUTPUT CURRENT (mA)
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Micrel, Inc.
MIC2808
Typical Characteristics (LDO1/LDO2 cont.)
LDO1/LDO2 Output Noise
Spectral Density
10
1
0.1
0.01
V
V
= 4.2V
IN
OUT
= 2.85V
= 1µF
C
OUT
0.001
0.01 0.1
1
10 100 1000 10000
FREQUENCY (kHz)
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Micrel, Inc.
MIC2808
Functional Characteristics
DC/DC PWM Waveforms
DC/DC Start-Up Waveforms
V
V
= 3.6V
IN
OUT
= 300mA
= 1.8V
I
OUT
L = 4.7µH
= 1µF
V
V
= 3.6V
I
= 100mA
C
= 1µF
IN
OUT
= 1.8V L = 4.7µH
OUT
OUT
C
OUT
Time (10µs/div )
Time (400ns/div)
DC/DC Load Transient
300mA
V
V
= 3.6V
IN
= 1.8V
OUT
L = 4.7µH
= 1µF
C
10mA
OUT
Time (20µs/div )
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Micrel, Inc.
MIC2808
Functional Characteristics (continued)
LDO1 Start-Up Waveforms
LDO1 Load Transient
200mA
V
V
= 3.6V
10mA
IN
OUT
= 200mA
= 2.85V
V
V
= 3.6V
IN
I
OUT
= 2.85V
OUT
OUT
C
= 2.2µF
OUT
C
= 2.2µF
Time (10µs/div)
Time (20µs/div)
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Micrel, Inc.
MIC2808
Functional Diagram
MIC2808 Block Diagram
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Micrel, Inc.
MIC2808
VIN
Device Functional Description
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*.
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
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 (95mꢀ typical) P-
Channel MOSFET switch. The feedback signal provides
the control path to set the output at three times the DAC
voltage.
amplifier applications.
Also where high power is
required, the step-down PWM regulator has a bypass
mode where an internal 95mꢀ switch connects the OUT
and PVIN pins together.
SW
Pin Functional Description
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.
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 95mꢀ 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 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).
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.
M9999-071709-A
July 2009
13
Micrel, Inc.
MIC2808
Inductor Selection
Component 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:
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.
⎛
⎞
VOUT
⎜
⎟
⎟
VOUT 1−
⎜
V
IN
⎝
⎠
IPK = IOUT
+
2× f ×L
Input Capacitor
IPK:
Peak Inductor Current
Output/Load Current
Input Voltage
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.
IOUT
VIN:
:
VOUT
f:
:
Output Voltage
Switching Frequency of PWM Regulator
Inductor Value
L:
M9999-071709-A
July 2009
14
Micrel, Inc.
MIC2808
Typical Application Circuit
LDO2
C3
LDO2
VIN
OUT
OUT
1µF
GND
6.3V
L1
4.7µH/1A
VIN
C1
2.2µF
6.3V
VIN
SW
VOUT
C7
1µF
6.3V
C8
VIN
2.2µF
6.3V
EN2
EN2
PVIN
LDO1
C2
LDO1
BYP
MIC2808-xxYFT
C6
1µF
6.3V
1µF
AVIN
EN
GND
6.3V
C4
0.1µF
6.3V
EN
DAC
DAC
NC
C5
1µF
6.3V
EN1
EN1
AGND
PGND
Bill of Materials
Item
Part Number
Manufacturer
Description
Qty.
C1, C8 C1608X5R0J225K
C2,
TDK(1)
2.2µF Ceramic Capacitor, 6.3V, X5R, Size 0603
1µF Ceramic Capacitor, 6.3V, X5R, Size 0603
0.1µF Ceramic Capacitor, 6.3V, X5R, Size 0603
2
C3,
C1608X5R0J105K
TDK(1)
5
1
C5-C7
C4
C1608X5R0J104K
VLS3012T-4R7M1R0
CDH3D13-4R7NC
ME3220-472MLB
LQH32CN4R7M53
MIPF2520D4R7
TDK(1)
TDK(1)
Sumida(3)
Coilcraft(4)
Murata(5)
FDK(6)
4.7µH, 1.2A, 130mꢀ, L3.0mm x W3.0mm x H1.2mm
4.7µH, 1.15A, 175mꢀ, L3.0mm x W3.0mm x H1.4mm
4.7µH, 1.4A, 190mꢀ, L3.2mm x W2.5mm x H2.0mm
4.7µH, 650mA, 150mꢀ, L3.2mm x W2.5mm x H1.55mm
4.7µH, 1.1A, 110mꢀ, L2.5mm x W2.0mm x H1.0mm
L1
1
2MHz 600mA Buck with DAC Input, Bypass Switch and Dual
Low Noise 200mA/30mA LDOs
1
U1
MIC2808-xxYFT
Micrel, Inc.(7)
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
M9999-071709-A
July 2009
15
Micrel, Inc.
MIC2808
Top Layer
M9999-071709-A
July 2009
16
Micrel, Inc.
MIC2808
Bottom Layer
M9999-071709-A
July 2009
17
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.
M9999-071709-A
July 2009
18
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