Document
Features
n Wide Operating Input Voltage Range: 4V to 140V n Internal Low Resistance Power MOSFET n No Compensation Required n Adjustable 100mA to 400mA Maximum Output
Current n Low Dropout Operation: 100% Duty Cycle n Low Quiescent Current: 12µA n Wide Output Range: 0.8V to VIN n 0.8V ±1% Feedback Voltage Reference n Precise RUN Pin Threshold n Internal or External Soft-Start n Programmable 1.8V, 3.3V, 5V or Adjustable Output n Few External Components Required n Programmable Input Overvoltage Lockout n Thermally Enhanced High Voltage MSOP Package
Applications
n Industrial Control Supplies n Medical Devices n Distributed Power Systems n Portable Instruments n Battery-Operated Devices n Avionics n Automotive
LTC7138 High Efficiency, 140V
400mA Step-Down Regulator
Description
The LTC®7138 is a high efficiency step-down DC/DC regulator with internal power switch that draws only 12μA typical DC supply current while maintaining a regulated output voltage at no load. The LTC7138 can supply up to 400mA load current and features a programmable peak current limit that provides a simple method for optimizing efficiency and for reducing output ripple and component size. The LTC7138’s combination of Burst Mode® operation, integrated power switch, low quiescent current, and programmable peak current limit provides high efficiency over a broad range of load currents. With its wide input range of 4V to 140V and programmable overvoltage lockout, the LTC7138 is a robust regulator suited for regulating from a wide variety of power sources. Additionally, the LTC7138 includes a precise run threshold and soft-start feature to guarantee that the power system start-up is well-controlled in any environment. A feedback comparator output enables multiple LTC7138s to be connected in parallel for higher current applications. The LTC7138 is available in a thermally enhanced high voltage-capable 16-lead MSE package with four missing pins.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Typical Application
5V to 140V Input to 5V Output, 400mA Step-Down Regulator
VIN 5V TO 140V CIN
1µF 250V
VIN SW LTC7138
RUN ANODE
SS
VPRG1
VFB
VPRG2
OVLO
GND
L1 220µH
VOUT 5V COUT 400mA 22µF
7138 TA01a
EFFICIENCY (%)
Efficiency and Power Loss vs Load Current
100 90 EFFICIENCY
80
70
60 1000
50
40 POWER LOSS
100
30
20 10 0
0.1
VIN = 12V 10 VIN = 48V VIN = 140V 1 1 10 100 1000
LOAD CURRENT (mA)
7138 TA01b
For more information www.linear.com/LTC7138
POWER LOSS (mW)
7138f
1
LTC7138
Absolute Maximum Ratings
(Note 1)
VIN Supply Voltage.................................... –0.3V to 140V RUN Voltage............................................. –0.3V to 140V SS, FBO, OVLO, ISET Voltages....................... –0.3V to 6V VFB, VPRG1, VPRG2 Voltages.......................... –0.3V to 6V Operating Junction Temperature.