LT1676_15 Datasheet, PDF (1/16 Pages) Linear Technology – Wide Input Range, High Efficiency, Step-Down Switching Regulator

LT1676
Wide Input Range,
High Efficiency, Step-Down
Switching Regulator
FEATURES
s _{Wide Input Range: 7.4V to 60V}
s _{700mA Peak Switch Current Rating}
s _{Adaptive Switch Drive Maintains Efficiency at High}
Load Without Pulse Skipping at Light Load
s _{True Current Mode Control}
s _{100kHz Fixed Operating Frequency}
s _{Synchronizable to 250kHz}
s _{Low Supply Current in Shutdown: 30µA}
s _{Available in 8-Pin SO and PDIP Packages}
U
APPLICATIO S
s _{Automotive DC/DC Converters}
s _{Telecom 48V Step-Down Converters}
s _{Cellular Phone Battery Charger Accessories}
s _{IEEE 1394 Step-Down Converters}
DESCRIPTIO
The LT^®1676 is a wide input range, high efficiency Buck
(step-down) switching regulator. The monolithic die in-
cludes all oscillator, control and protection circuitry. The
part can accept input voltages as high as 60V and contains
an output switch rated at 700mA peak current. Current
mode control offers excellent dynamic input supply rejec-
tion and short-circuit protection.
The LT1676 contains several features to enhance effi-
ciency. The internal control circuitry is normally powered
via the V_CC pin, thereby minimizing power drawn directly
from the V_IN supply (see Applications Information). The
action of the LT1676 switch circuitry is also load depen-
dent. At medium to high loads, the output switch circuitry
maintains high rise time for good efficiency. At light loads,
rise time is deliberately reduced to avoid pulse skipping
behavior.
The available SO-8 package and 100kHz switching fre-
quency allow for minimal PC board area requirements.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
V_IN
8V TO 50V
+
5
1
V_IN
2
SHDN V_CC
3
V_SW
39µF
63V
LT1676
6
SYNC
7
FB
8
V_C
GND
4
220µH*
+
MBR160
100µF
10V
5V
400mA
36.5k
1%
2200pF
22k
100pF
12.1k
1%
*65T #30 ON MAGNETICS
MPP #55030
1676 F01
Figure 1
Efficiency vs V_IN and I_LOAD
90
80
70
60
50
40 ^VIN ^{= 12V}
V_IN = 24V
30 _{VIN = 36V}
20 ^{VIN = 48V}
1
10
100
I_LOAD (mA)
1000
1676 TA01
1