LINEAR TECHNOLOGY LTC1625 No RSENSE TM Current Mode Synchronous Step-Down Switching Regulator
Summary
The LTC1625 is a high-efficiency synchronous step-down switching regulator controller engineered for reliable power management in portable electronics. It eliminates the need for external sense resistors while providing stable, high-current operation across a wide voltage range (3.7V to 36V input). This manual provides comprehensive technical details, including operational modes like Burst Mode and Forced Continuous Control, advanced protection features, and typical application circuits, making it essential for designers building notebooks, PDAs, battery chargers, and cellular devices requiring optimal power conversion efficiency.
Page 1 Text Content
LTC1625
TM Current Mode
No RSENSE Synchronous Step-Down Switching Regulator
FEATURES DESCRIPTION Highest Efficiency Current Mode Controller The LTC®1625 is a synchronous step-down switching No Sense Resistor Required regulator controller that drives external N-Channel power Stable High Current Operation MOSFETs using few external components. Current mode Dual N-Channel MOSFET Synchronous Drive control with MOSFET VDS sensing eliminates the need for Wide VIN Range: 3.7V to 36V a sense resistor and improves efficiency. The frequency of Wide VOUT Range: 1.19V to VIN a nominal 150k Hz internal oscillator can be synchronized ±1% 1.19V Reference to an external clock over a 1.5:1 frequency range.
Programmable Fixed Frequency with Injection Lock
Burst Mode TM operation at low load currents reduces
Very Low Drop Out Operation: 99% Duty Cycle
switching losses and low dropout operation extends oper-
Forced Continuous Mode Control Pin
ating time in battery-powered systems. A forced continu-
Optional Programmable Soft Start
ous mode control pin can assist secondary winding
Pin Selectable Output Voltage
regulation by disabling Burst Mode operation when the
Foldback Current Limit
main output is lightly loaded.
Output Overvoltage Protection
Logic Controlled Micropower Shutdown: IQ < 30µA Fault protection is provided by foldback current limiting Available in 16-Lead Narrow SSOP and SO Packages and an output overvoltage comparator. An external ca-
EF FI CI EN CY
pacitor attached to the RUN/SS pin provides soft start capability for supply sequencing. A wide supply range
APPLICATIONS allows operation from 3.7V (3.9V for LTC1625I) to 36V at
the input and 1.19V to VIN at the output.
Notebook and Palmtop Computers, PDAs
, LTC and LT are registered trademarks of Linear Technology Corporation.
Cellular Telephones and Wireless Modems
No RSENSE and Burst Mode are trademarks of Linear Technology Corporation.
Battery Chargers Distributed Power
TYPICAL APPLICATION
Efficiency vs Load Current
VIN VIN = 10V
SYNC VIN 5V TO VOUT = 5V
RUN/SS TK
0.1µF TG
Si4410DY L1 ×2
LTC1625 VOUT = 3.3V
10µH VOUT
ITH SW
CB 0.22µF 3.3V
RC BOOST COUT
10k DB 100µF
MBRS140T3
CMDSH-3 CVCC 4.7µF 10V
CC VPROG INTVCC
SGND BG
Si4410DY
VOSENSE PGND
0.01 0.1 LOAD CURRENT (A)
Figure 1. High Efficiency Step-Down Converter
1625 TA01
Page Summary Contents For LINEAR TECHNOLOGY LTC1625 No RSENSE TM Current Mode Synchronous Step-Down Switching Regulator
Manual Details
| Brand | Current |
|---|---|
| Pages | 24 |
| File Size | 378.39 KB |
| Published | May 31, 2026 |
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Frequently Asked Questions
What is the input voltage range for this regulator?
It supports operation from 3.7V up to 36V at the input.
Is an external current sense resistor needed?
No, it does not require a sense resistor because the control uses MOSFET V sensing.
Which operational mode is best for low load currents?
Burst Mode operation helps reduce power consumption when the circuit is lightly loaded.
What protection features are included to prevent failure?
It includes output overvoltage protection and foldback current limiting.
Can I synchronize the internal oscillator with an external clock?
Yes, the 150kHz internal oscillator can be synchronized to an external clock over a 1.5:1 frequency range.