Document
MIC3385
8MHz Inductorless Buck Regulator with LDO Standby Mode
General Description
The Micrel MIC3385 is a high-efficiency inductorless buck regulator that features a LOWQ® LDO standby mode that draws only 18µA of quiescent current. The MIC3385 requires no external inductor enabling an ultra-low noise, small size, and high efficiency solution for portable power applications.
In PWM mode, the MIC3385 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 MIC3385 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 MIC3385 is available in the 14-pin 3mm x 3.5mm 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.
LOWQ®
Features
• 2.7 to 5.5V supply voltage • Light load LOWQ® LDO mode
– 18µA 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 • Ultra-fast transient response • No external inductor required • Enables sub 1mm profile solution • Fully integrated MOSFET switches • Micropower shutdown • Thermal shutdown and current limit protection • Pb-free 14-pin 3x3.5x0.9mm MLF® package • –40°C to +125°C junction temperature range
Applications
• Slim digital cameras • MP3 players • Portable power applications • Cellular phones • PDAs • USB peripherals
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
September 22, 2015
Revision 3.0
Micrel, Inc.
Typical Application
Adjustable Output Buck Regulator with LOWQ® Mode
MIC3385
2.5V OUT Efficiency
100 90 80 70 60 50 40 30 20 10 00
VIN=3.2V VIN=3.6V VIN=4.2V
100 200 300 400 500 600 OUTPUT CURRENT (mA)
Ordering Information
Part Number MIC3385YHL MIC3385-1.5YHL
Voltage Adj. 1.5V
Temperature Range –40° to +125°C –40° to +125°C
Package 14-Pin 3mm x 3.5mm MLF® 14-Pin 3mm x 3.5mm MLF®
Notes: 1. MLF® is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free. 2. Other voltage options available. Please contact Micrel for details.
Lead Finish Pb-free Pb-free
September 22, 2015
2
Revision 3.0
Micrel, Inc.
Pin Configuration
FB 1 VIN 2 LOWQ 3 EN 4 OUT 5 OUT 6 OUT 7
14 BIAS 13 LDO 12 AVIN 11 GND 10 SW 9 SW 8 SW
14- Pin 3mm x 3.5mm MLF® (HL)
MIC3385
Pin Description
Pin Number 1
Pin Name FB
2
VIN
3
LOWQ
4
EN
5,6,7 8,9,10
11
12
OUT SW GND
AVIN
13
LDO
14
BIAS
Pin Function
Feedback. Input to the error amplifier. Connect to the external resistor divider network to set the output voltage.
Supply Voltage (Input): Supply voltage for the internal switches and drivers.
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.
Enable (Input). Logic low will shut down the device, reducing the quiescent current to less than 5µA. Switch Output after inductor.
Switch (Output): Internal power MOSFET output switches before Inductor Power Ground. Requires input capacitor to GND.
Analog Supply Voltage (Input): Supply voltage for the analog control circuitry and LDO input power. Requires bypass capacitor to GND.
LDO Output (Output): Connect to VOUT for LDO mode operation.
Internal circuit bias supply. Must be de-coupled to signal ground with a 0.1µF capacitor and should not be loaded.
September 22, 2015
3
Revision 3.0
Micrel, Inc.
MIC3385
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 Storage Temperature (Ts) ......................... –60°C to +150°C EDS Rating(3).................................................................. 3kV
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 Therm.