MIC2285A Datasheet PDF - MICREL

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MIC2285A
MICREL

Part Number MIC2285A
Description 8MHz PWM Synchronous Buck Regulator
Page 14 Pages


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MIC2285A
8MHz PWM Synchronous Buck Regulator
with LDO Standby Mode
General Description
The Micrel MIC2285A is a high efficiency 8MHz
PWM synchronous buck (step-down) regulator that
features a LOWQ® LDO standby mode that draws
only 20µA of quiescent current. The MIC2285A
allows an ultra-low noise, small size, and high
efficiency solution for portable power applications.
In PWM mode, the MIC2285A operates with a
constant frequency 8MHz PWM control. Under light
load conditions, such as in system sleep or standby
modes, the PWM switching operation can be
disabled to reduce switching losses. In this light load
LOWQ® mode, the LDO maintains the output voltage
and draws only 18µA of quiescent current. The LDO
mode of operation saves battery life while not
introducing spurious noise and high ripple as
experienced with pulse skipping or bursting mode
regulators.
The MIC2285A operates from 2.7V to 5.5V input and
features internal power MOSFETs that can supply
up to 600mA output current in PWM mode. It can
operate with a maximum duty cycle of 100% for use
in low-dropout conditions.
The MIC2285A is available in the 10-pin 2mm x
2mm Thin MLF® package with a junction operating
range from –40°C to +125°C.
Data sheets and support documentation can be
found on Micrel’s web site at: www.micrel.com.
Features
2.7 to 5.5V supply/input voltage
Light load LOWQ® LDO mode
– 20µA quiescent current
– Low noise, 75µVrms
8MHz PWM mode
– Output current to 600mA
– >90% efficiency
– 100% maximum duty cycle
Adjustable output voltage option down to 1V
– Fixed output voltage options available
Ultra-fast transient response
Requires only a 0.47µH inductor
Enables sub 0.55mm profile solution
Fully integrated MOSFET switches
Micropower shutdown
Thermal shutdown and current limit protection
10-pin 2mm x 2mm x 0.55mm MLF® package
–40°C to +125°C junction temperature range
Applications
Cellular phones
PDAs
USB peripherals
____________________________________________________________________________________________________
Typical Application
www.DataSheet4U.com
Adjustable Output Buck Regulator with LOWQ® Mode
100
90
80
70
60
50
40
30
20
10
00
2.5VOUT Efficiency
VIN=3.2V
VIN=3.6V
VIN=4.2V
100 200 300 400 500 600
OUTPUT CURRENT (mA)
LOWQ is a registered trademark of Micrel, Inc
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
August 2007
M9999-083107-B



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Micrel, Inc.
MIC2285A
Ordering Information
Part Number
MIC2285AYMT
Marking
WPA
Output
Voltage*
Adj.
Junction
Temperature Range
–40° to +125°C
Package
10-Pin 2x2 Thin MLF®
Note
* For other voltage options available, please contact Micrel Marketing for details.
MLF® is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
Lead Finish
Pb-free
Pin Configuration
AGND 1
LDO 2
BIAS 3
AVIN 4
FB 5
10 PGND
9 SW
8 VIN
7 LOWQ
6 EN
10-Pin 2mm x 2mm Thin MLF® (MT)
Pin Description
Pin Number
1
2
3
4
5
6
7
www.DataSheet4U.co8m
9
10
Pin Name
AGND
LDO
BIAS
AVIN
FB
EN
_____
LOWQ
VIN
SW
PGND
Pin Function
Analog (signal) Ground.
LDO Output (Output): Connect to VOUT for LDO mode operation.
Internal circuit bias supply. Must be decoupled to signal ground with a 0.1µF
capacitor and should not be loaded.
Analog Supply Voltage (Input): Supply voltage for the analog control circuitry
and LDO input power. Requires bypass capacitor to GND.
Feedback. Input to the error amplifier. For the Adjustable option, connect to the
external resistor divider network to set the output voltage. For fixed output
voltage options, connect to VOUT and an internal resistor network sets the output
voltage.
Enable (Input). Logic low will shut down the device, reducing the quiescent
current to less than 5µA.
Enable LDO Mode (Input): Logic low enables the internal LDO and disables the
PWM operation. Logic high enables the PWM mode and disables the LDO
mode.
Supply Voltage (Input): Supply voltage for the internal switches and drivers.
Switch (Output): Internal power MOSFET output switches.
Power Ground.
August 2007
2 M9999-083107-B



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Micrel, Inc.
MIC2285A
Absolute Maximum Ratings(1)
Supply Voltage (VIN) ............................................ +6V
Output Switch Voltage (VSW) ............................... +6V
Output Switch Current (ISW) ................................... 2A
Logic Input Voltage (VEN,VLOWQ) ..............–0.3V to VIN
SEStoDraRgeatTinegm(3p) .e..r.a..t.u..r..e...(.T..s.).................................–..6..0..°.C....t.o...+..1..530k°CV
Operating Ratings(2)
Supply Voltage (VIN)............................+2.7V to +5.5V
Logic Input Voltage (VEN,VLOWQ) ............. –0.3V to VIN
Junction Temperature (TJ) .............. –40°C to +125°C
Junction Thermal Resistance
2x2 MLF-10L (θJA) ................................... 60°C/W
Electrical Characteristics(4)
VIN = VEN = VLOWQ =3.6V; L = 0.47µH; COUT = 10µF; TA = 25°C, unless noted. Bold values indicate –40°C< TJ < +125°C
Parameter
Condition
Min Typ Max Units
Supply Voltage Range
2.7 5.5 V
Under-Voltage Lockout
Threshold
(turn-on)
2.45 2.55 2.65
V
UVLO Hysteresis
100 mV
Quiescent Current, PWM
mode
VFB = 0.9 * VNOM (not switching)
790 900
µA
Quiescent Current, LDO
mode
VLOWQ = 0V;IOUT = 0mA
20 29 µA
Shutdown Current
[Adjustable] Feedback
Voltage
VEN = 0V
±1%
± 2% (over temperature)
0.01 5
0.99 1 1.01
0.98 1.02
µA
V
V
[Fixed Output] Voltages
Nominal VOUT tolerance
–1 +1 %
–2 +2 %
FB pin input current
1 nA
Current Limit in PWM Mode
Output Voltage Line
Regulation
Output Voltage Load
Regulation, PWM Mode
VFB = 0.9 * VNOM
VOUT > 2V; VIN = VOUT+300mV to 5.5V; ILOAD= 100mA
VOUT < 2V; VIN = 2.7V to 5.5V; ILOAD= 100mA
20mA < ILOAD < 300mA
0.75
1
0.13
0.2
1.85
0.8
A
%
%
Output Voltage Load
Regulation, LDO Mode
100µA < ILOAD < 50mA
VLOWQ = 0V
0.5 1
%
Maximum Duty Cycle
PWM Switch ON-
Resistance
Oscillator Frequency
VFB 0.4V
ISW = 50mA VFB = 0.7VFB_NOM (High Side Switch)
ISW = -50mA VFB = 1.1VFB_NOM (Low Side Switch)
100 %
0.4
0.4
7.2 8 8.8 MHz
LOWQ Threshold Voltage
0.5 0.85 1.3
V
LOWQ Input Current
Enable Threshold
Enable Input Current
www.DLaDtaOShDeerot4pUou.ctoVmoltage
IOUT = 50mA Note 5
0.1 2
0.5 0.85 1.3
0.1 2
110
µA
V
µA
mV
August 2007
3 M9999-083107-B



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Micrel, Inc.
MIC2285A
Parameter
Output Voltage Noise
LDO Current Limit
Over-Temperature
Shutdown
Over-Temperature
Hysteresis
Condition
LOWQ = 0V; COUT = 10µF, 10Hz to 100kHz
LOWQ = 0V; VOUT = 0V (LDO Mode)
Min Typ Max Units
75 µVrms
60 120
160
mA
°C
20 °C
Notes
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model: 1.5kin series with 100pF.
4. Specification for packaged product only.
5. Dropout voltage is defined as the input-to-output differential at which the output voltage drops 2% below its nominal value that is
initially measured at a 1V differential. For outputs below 2.7V, the dropout voltage is the input-to-output voltage differential with a
minimum input voltage of 2.7V.
www.DataSheet4U.com
August 2007
4 M9999-083107-B



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