LTC1434_15 Datasheet, PDF (1/20 Pages) Linear Technology – 450mA, Low Noise Current Mode Step-Down DC/DC Converters

FEATURES
s _{High Efficiency: Up to 93%}
s _{Constant Frequency Adaptive Power}^TM _Operation
s _{Input Voltage Range: 3V to 13.5V}
s _{Internal 0.6Ω Power Switch (VIN = 10V)}
s _{Low Dropout Operation: 100% Duty Cycle}
s _{Low-Battery Detector}
s _{Internal Power-On Reset Timer}
s _{Current Mode Operation for Excellent Line and Load}
Transient Response
s _{Low Quiescent Current: 470µA}
s _{Shutdown Mode Draws Only 15µA Supply Current}
s _{±1% Reference Accuracy}
s _{Available in 16- and 20-Lead Narrow SSOP}
U
APPLICATIONS
s _{Cellular Telephones}
s _{Portable Instruments}
s _{Wireless Modems}
s _{RF Communications}
s _{Distributed Power Systems}
s _Scanners
s _{Battery-Powered Equipment}
, LTC and LT are registered trademarks of Linear Technology Corporation.
Adaptive Power is a trademark of Linear Technology Corporation.
LTC1433/LTC1434
450mA, Low Noise
Current Mode Step-Down
DC/DC Converters
DESCRIPTION
The LTC^®1433/LTC1434 are monolithic pulse width modu-
lated step-down DC/DC converters. By utilizing current
mode switching techniques, they provide excellent AC and
DC load and line regulation. Both devices operate at a fixed
frequency with the LTC1434 phase-lockable to an external
clock signal.
Both devices incorporate two internal P-channel power
MOSFETs with a parallel combined resistance of 0.6Ω (at
a supply of 10V). The Adaptive Power output stage selec-
tively drives one or both of the switches at frequencies up
to 700kHz to reduce switching losses and maintain high
efficiencies at low output currents.
The LTC1433/LTC1434 are capable of supplying up to
450mA of output current and boasts a ±2.4% output
voltage accuracy. An internal low-battery detector has the
same level of accuracy as the output voltage. A power-on
reset timer (POR) is included which generates a signal
delayed by 65536/f_CLK (300ms typ) after the output is
within 5% of the regulated output voltage.
Ideal for current sensitive applications, the devices draw
only 470µA of quiescent current. In shutdown the devices
draw a mere 15µA. To further maximize the life of the
battery source, the internal P-channel MOSFET switch is
turned on continuously in dropout.
TYPICAL APPLICATION
68µF**
0.1µF _20V
V_OUT
3.3V
L1
100µH
+ _100µF*
10V
D1
0.1µF
1
SSW
2
NC
16
PWRV_IN
PGND 15
3
14
BSW
SV_IN
4
LTC1433
13
NC
C_OSC
5
12
SGND
POR
6
RUN/SS
7
LBO
8
LBI
11
I_TH
10
V_OSENSE
9
V_PROG
V_IN
3.5V TO 12V
10k
POWER-ON
RESET
5.1k
680pF
47pF
6800pF
D1: MOTOROLA MBRS130LT3 *AVX TPSD107M010R0100
L1: COILCRAFT D03316-104 ** AVX TPSE686M020R0150
Figure 1. High Efficiency Step-Down Converter
1433/34 F01
LTC1433 Efficiency for
V_OUT = 3.3V
100
90
V_IN = 5V
80
V_IN = 12V
70
V_IN = 9V
60
50
40
0.001
0.01
0.1
LOAD CURRENT (A)
1
1433/34 TA01
1