LTC3704_15 Datasheet, PDF (1/28 Pages) Linear Technology – Wide Input Range, No RSENSE Positive-to-Negative DC/DC Controller

LTC3704
Wide Input Range, No R_SENSE^TM
Positive-to-Negative DC/DC Controller
FEATURES
DESCRIPTIO
■ _{High Efficiency Operation (No Sense}
Resistor Required)
■ _{Wide Input Voltage Range: 2.5V to 36V}
■ _{Current Mode Control Provides Excellent Transient}
Response
■ _{High Maximum Duty Cycle (Typ 92%)}
■ _{±1% Internal Voltage Reference}
■ _{±2% RUN Pin Threshold with 100mV Hysteresis}
■ _{Micropower Shutdown: IQ = 10μA}
■ _{Programmable Switching Frequency}
(50kHz to 1MHz) with One External Resistor
■ _{Synchronizable to an External Clock Up to 1.3 × fOSC}
■ _{User-Controlled Pulse Skip or Burst Mode}^® _Operation
■ _{Internal 5.2V Low Dropout Voltage Regulator}
■ _{Capable of Operating with a Sense Resistor for High}
Output Voltage Applications (V_DS >36V)
■ _{Small 10-Lead MSOP Package}
U
APPLICATIO S
■ _{SLIC Power Supplies}
■ _{Telecom Power Supplies}
■ _{Portable Electronic Equipment}
■ _{Cable and DSL Modems}
■ _{Router Supplies}
The LTC^®3704 is a wide input range, current mode,
positive-to-negative DC/DC controller that drives an
N-channel power MOSFET and requires very few external
components. Intended for low to high power applications,
it eliminates the need for a current sense resistor by
utilizing the power MOSFET’s on-resistance, thereby maxi-
mizing efficiency.
The IC’s operating frequency can be set with an external
resistor over a 50kHz to 1MHz range, and can be synchro-
nized to an external clock using the MODE/SYNC pin.
Burst Mode operation at light loads, a low minimum
operating supply voltage of 2.5V and a low shutdown
quiescent current of 10μA make the LTC3704 ideally
suited for battery-operated systems.
For applications requiring constant frequency operation,
the Burst Mode operation feature can be defeated using
the MODE/SYNC pin. Higher than 36V switch voltage
applications are possible with the LTC3704 by connecting
the SENSE pin to a resistor in the source of the power
MOSFET.
The LTC3704 is available in the 10-lead MSOP package.
, LTC, LT and LTM are registered trademarks of Linear Technology Corporation. Burst
Mode is a registered trademark of Linear Technology Corporation. No R_SENSE is a
registered trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including 5847554, 5731694.
TYPICAL APPLICATIO
R_C
3k
C_C1
4.7nF
R1
1M
RUN
SENSE
I_TH
V_IN
LTC3704
NFB
FREQ
INTV_CC
GATE
MODE/SYNC GND
R_T
80.6k
1%
R_FB1
1.21k
1%
R_FB2
3.65k
1%
C_VCC
4.7μF
•
L1*
•
C_DC
L2*
47μF
M1
D1
C_IN
47μF
V_IN
5V to 15V
V_OUT
–5.0V
3A to 5A
C_OUT
100μF
(X2)
GND
3704 TA01
C_IN, C_DC : TDK C5750X5R1C476M
C_OUT: TDK C5750X5R0J107M
C_VCC: TAIYO YUDEN LMK316BJ475ML
D1: MBRD835L (ON SEMICONDUCTOR)
L1, L2: BH ELECTRONICS BH510-1009
M1: Si4884 (SILICONIX/VISHAY)
Figure 1. High Efficiency Positive to Negative Supply
Conversion Efficiency
100
90
80
V_IN = 5V
70
V_IN = 15V
60
V_IN = 10V
50
40
30
20
0.001
0.01
0.1
1.0
10
OUTPUT CURRENT (A)
3704 TA01b
3704fb
1