Datasheet LTC3704 (Analog Devices)

LTC3704 Wide Input Range, No R TM SENSE Positive-to-Negative DC/DC Controller
U FEATURES DESCRIPTIO
■
High Efficiency Operation (No Sense
The LTC®3704 is a wide input range, current mode,
Resistor Required)
positive-to-negative DC/DC controller that drives an ■
Wide Input Voltage Range: 2.5V to 36V
N-channel power MOSFET and requires very few external ■
Current Mode Control Provides Excellent Transient
components. Intended for low to high power applications,
Response
it eliminates the need for a current sense resistor by ■
High Maximum Duty Cycle (Typ 92%)
utilizing the power MOSFET’s on-resistance, thereby maxi- ■ ±
1% Internal Voltage Reference
mizing efficiency. ■ ±
2% RUN Pin Threshold with 100mV Hysteresis
The IC’s operating frequency can be set with an external ■ Micropower Shutdown: IQ = 10μA resistor over a 50kHz to 1MHz range, and can be synchro- ■ Programmable Switching Frequency nized to an external clock using the MODE/SYNC pin. (50kHz to 1MHz) with One External Resistor Burst Mode operation at light loads, a low minimum ■ Synchronizable to an External Clock Up to 1.3 × fOSC operating supply voltage of 2.5V and a low shutdown ■ User-Controlled Pulse Skip or Burst Mode® Operation quiescent current of 10μA make the LTC3704 ideally ■ Internal 5.2V Low Dropout Voltage Regulator suited for battery-operated systems. ■ Capable of Operating with a Sense Resistor for High Output Voltage Applications (V For applications requiring constant frequency operation, DS >36V) ■ Small 10-Lead MSOP Package the Burst Mode operation feature can be defeated using
U
the MODE/SYNC pin. Higher than 36V switch voltage
APPLICATIO S
applications are possible with the LTC3704 by connecting the SENSE pin to a resistor in the source of the power ■ SLIC Power Supplies MOSFET. ■ Telecom Power Supplies ■ The LTC3704 is available in the 10-lead MSOP package. Portable Electronic Equipment ■ Cable and DSL Modems , LTC, LT and LTM are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. No RSENSE is a ■ Router Supplies registered trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5847554, 5731694.
U TYPICAL APPLICATIO
VIN • 5V to 15V
Conversion Efficiency
R1 L1* V 1M OUT 100 –5.0V • 3A to 5A RUN SENSE 90 L2* C I DC V TH VIN 80 IN = 5V 47μF LTC3704 70 VIN = 15V RC NFB INTVCC COUT 3k 100μF 60 FREQ GATE M1 (X2) VIN = 10V MODE/SYNC GND D1 50 EFFICIENCY (%) CC1 4.7nF R 40 T C C 80.6k VCC IN 4.7μF 47μF 1% 30 GND RFB1 RFB2 3704 TA01 20 1.21k 3.65k 0.001 0.01 0.1 1.0 10 1% 1% OUTPUT CURRENT (A) CIN, CDC : TDK C5750X5R1C476M D1: MBRD835L (ON SEMICONDUCTOR) 3704 TA01b COUT: TDK C5750X5R0J107M L1, L2: BH ELECTRONICS BH510-1009 CVCC: TAIYO YUDEN LMK316BJ475ML M1: Si4884 (SILICONIX/VISHAY)
Figure 1. High Efficiency Positive to Negative Supply
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