LTC1436A_15 Datasheet, PDF (1/28 Pages) Linear Technology – High Efficiency Low Noise Synchronous Step-Down Switching Regulators

LTC1436A
LTC1436A-PLL/LTC1437A
High Efficiency Low Noise
Synchronous Step-Down
Switching Regulators
FEATURES
■ _{Maintains Constant Frequency at Low Output Currents}
■ _{Programmable Fixed Frequency (PLL Lockable)}
■ _{Wide VIN Range: 3.5V to 36V Operation}
■ _{Low Minimum On-Time (≤300ns) for High}
Frequency, Low Duty Cycle Applications
■ _{Dual N-Channel MOSFET Synchronous Drive}
■ _{Very Low Dropout Operation: 99% Duty Cycle}
■ _{Low Dropout, 0.5A Linear Regulator for CPU I/O}
or Low Noise Audio Supplies
■ _{Built-In Power-On Reset Timer}
■ _{Programmable Soft Start}
■ _{Low-Battery Detector}
■ _{Remote Output Voltage Sense}
■ _{Foldback Current Limiting (Optional)}
■ _{Pin Selectable Output Voltage}
■ _{Logic Controlled Micropower Shutdown: IQ < 25µA}
■ _{Output Voltages from 1.19V to 9V}
■ _{Available in 24-Lead Narrow SSOP and 28-Lead}
SSOP Packages
U
APPLICATIO S
■ _{Notebook and Palmtop Computers, PDAs}
■ _{Cellular Telephones and Wireless Modems}
■ _{Portable Instruments}
■ _{Battery-Operated Devices}
■ _{DC Power Distribution Systems}
DESCRIPTIO
The LTC^®1436A/LTC1437A are synchronous step-down
switching regulator controllers that drive external
N-channel power MOSFETs in a phase lockable, fixed
frequency architecture. The Adaptive Power^TM output stage
selectively drives two N-channel MOSFETs at frequencies
up to 400kHz while reducing switching losses to maintain
high efficiencies at low output currents.
An auxiliary 0.5A linear regulator using an external PNP
pass device provides a low noise, low dropout voltage
source. A secondary winding feedback control pin (SFB)
guarantees regulation regardless of the load on the main
output by forcing continuous operation.
An additional comparator is available for use as a low-
battery detector. A power-on reset timer (POR) is included
which generates a signal delayed by 65536/f_CLK (300ms
typically) after the output is within 5% of the regulated
output voltage. Internal resistive dividers provide pin
selectable output voltages with remote sense capability.
The operating current level is user-programmable via an
external current sense resistor. Wide input supply range
allows operation from 3.5V to 30V (36V maximum).
, LTC and LT are registered trademarks of Linear Technology Corporation.
Adaptive Power is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5481178, 6304066, 5929620, 6580258,
5705919, 5731731
TYPICAL APPLICATIO
C_OSC
43pF
C_SS
0.1µF
R_C
10k
C_OSC
V_IN
TGL
RUN/SS
TGS
C_C
510pF
100pF
I_TH
SGND
LTC1436A
SW
INTV_CC
BOOST
V_PROG
V_OSENSE
SENSE ^–
BG
PGND
SENSE⁺
1000pF
V_IN
4.5V TO 22V
M3
IRLML2803
D_B
CMDSH-3
C_B
0.1µF
M1
Si4412DY
L1
4.7µH
+
C_IN
22µF
35V
×2
R_SENSE
0.02Ω
+
4.7µF
M2
Si4412DY
D1
MBRS140T3
Figure 1. High Efficiency Step-Down Converter
R1
35.7k ₊
R2
102k
V_OUT
1.6V
5A
C_OUT
100µF
6.3V
×2
1436 F01
14367afb
1