LT1076_15 Datasheet, PDF (1/16 Pages) Linear Technology – Step-Down Switching Regulator

LT1074/LT1076
Step-Down Switching
Regulator
FEATURES
■ _{5A Onboard Switch (LT1074)}
■ _{Operates Up to 60V Input}
■ _{100kHz Switching Frequency}
■ _{Greatly Improved Dynamic Behavior}
■ _{Available in Low Cost 5 and 7-Lead Packages}
■ _{Only 8.5mA Quiescent Current}
■ _{Programmable Current Limit}
■ _{Micropower Shutdown Mode}
U
APPLICATIO S
■ _{Buck Converter with Output Voltage Range of 2.5V}
to 50V
■ _{Tapped-Inductor Buck Converter with 10A Output}
at 5V
■ _{Positive-to-Negative Converter}
■ _{Negative Boost Converter}
■ _{Multiple Output Buck Converter}
DESCRIPTIO
The LT^®1074 is a 5A (LT1076 is rated at 2A) monolithic
bipolar switching regulator which requires only a few
external parts for normal operation. The power switch, all
oscillator and control circuitry, and all current limit com-
ponents, are included on the chip. The topology is a classic
positive “buck” configuration but several design innova-
tions allow this device to be used as a positive-to-negative
converter, a negative boost converter, and as a flyback
converter. The switch output is specified to swing 40V
below ground, allowing the LT1074 to drive a tapped-
inductor in the buck mode with output currents up to 10A.
The LT1074 uses a true analog multiplier in the feedback
loop. This makes the device respond nearly instanta-
neously to input voltage fluctuations and makes loop gain
independent of input voltage. As a result, dynamic behav-
ior of the regulator is significantly improved over previous
designs.
On-chip pulse by pulse current limiting makes the LT1074
nearly bust-proof for output overloads or shorts. The input
voltage range as a buck converter is 8V to 60V, but a self-
boot feature allows input voltages as low as 5V in the
inverting and boost configurations.
The LT1074 is available in low cost TO-220 or DD packages
with frequency pre-set at 100kHz and current limit at 6.5A
(LT1076 = 2.6A). A 7-pin TO-220 package is also available
which allows current limit to be adjusted down to zero. In
addition, full micropower shutdown can be programmed.
See Application Note 44 for design details.
A fixed 5V output, 2A version is also available. See LT1076-5.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
10V TO 40V
+
Basic Positive Buck Converter
L1**
50µH (LT1074)
100µH (LT1076)
V_IN
V_SW
LT1074
GND
C3^†
200µF
FB
V_C
R3
2.7k
C2
0.01µF
MBR745* ^R1
2.8k
1%
R2
2.21k
1% ₊
5V
5A * USE MBR340 FOR LT1076
** COILTRONICS #50-2-52 (LT1074)
#100-1-52 (LT1076)
PULSE ENGINEERING, INC.
#PE-92114 (LT1074)
#PE-92102 (LT1076)
HURRICANE #HL-AK147QQ (LT1074)
#HL-AG210LL (LT1076)
C1
† _{RIPPLE CURRENT RATING ≥ IOUT/2}
500µF
25V
LT1074•TA01
Buck Converter Efficiency
100
90
80
70
60
50
0
LT1074
V_OUT = 12V, V_IN = 20V
V_OUT = 5V, V _IN = 15V
L = 50µH TYPE 52 CORE
DIODE = MBR735
1
2
3
4
5
6
OUTPUT LOAD CURRENT (A)
LT1074•TPC27
sn1074 1074fds
1