LT1976 Datasheet, PDF (1/24 Pages) Linear Technology – High Voltage 1.5A, 200kHz Step-Down Switching Regulator with 100mA Quiescent Current

LT1976
High Voltage 1.5A, 200kHz
Step-Down Switching Regulator
with 100µA Quiescent Current
FEATURES
s _{Wide Input Range: 3.3V to 60V}
s _{1.5A Peak Switch Current}
s _{Burst Mode}^® _{Operation: 100µA Quiescent Current**}
s _{Low Shutdown Current: IQ < 1µA}
s _{Power Good Flag with Programmable Threshold}
s _{Load Dump Protection to 60V}
s _{200kHz Switching Frequency}
s _{Saturating Switch Design: 0.2Ω On-Resistance}
s _{Peak Switch Current Maintained Over}
Full Duty Cycle Range*
s _{1.25V Feedback Reference Voltage}
s _{Easily Synchronizable}
s _{Soft-Start Capability}
s _{Small 16-Pin Thermally Enhanced TSSOP Package}
U
APPLICATIO S
s _{High Voltage Power Conversion}
s _{14V and 42V Automotive Systems}
s _{Industrial Power Systems}
s _{Distributed Power Systems}
s _{Battery-Powered Systems}
DESCRIPTIO
The LT^®1976 is a 200kHz monolithic buck switching
regulator that accepts input voltages up to 60V. A high
efficiency 1.5A, 0.2Ω switch is included on the die along
with all the necessary oscillator, control and logic cir-
cuitry. Current mode topology is used for fast transient
response and good loop stability.
Innovative design techniques along with a new high volt-
age process achieve high efficiency over a wide input
range. Efficiency is maintained over a wide output current
range by employing Burst Mode operation at low currents,
utilizing the output to bias the internal circuitry, and by
using a supply boost capacitor to fully saturate the power
switch. Patented circuitry maintains peak switch current
over the full duty cycle range.* Shutdown reduces input
supply current to less than 1µA. External synchronization
can be implemented by driving the SYNC pin with logic-level
inputs. A single capacitor from the C_SS pin to the output
provides a controlled output voltage ramp (soft-start). The
device also has a power good flag with a programmable
threshold and time-out and thermal shutdown protection.
The LT1976 is available in a 16-pin TSSOP package with
exposed pad leadframe for low thermal resistance.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
*U.S. Patent 6,498,466 **See Burst Mode Operation section for conditions
TYPICAL APPLICATIO
14V to 3.3V Step-Down Converter with
100µA No Load Quiescent Current
V_IN
3.3V TO 60V
0.047µF
12.5k
4.7µF
100V
CER
100pF
1µF
V_IN BOOST
SHDN
SW
0.33µF 33µH ₄₁₄₈
LT1976 0.1µF
10MQ100N
V_C
C_SS
C_T
SYNC
GND
V_BIAS
FB
PGFB
PG
27pF
165k
1%
100k
1%
V_OUT
3.3V
1A
100µF
6.3V
TANT
1976 TA01
Supply Current vs
Input Voltage
150
V_OUT = 3.3V
T_A = 25°C
125
100
75
50
25
0
0 10 20 30 40 50 60
INPUT VOLTAGE (V)
1976 F05
Efficiency vs Load Current
100
90
V_OUT = 5V
80
T_A = 25°C
70
V_OUT = 3.3V
60
50
40
30
20
10
0
0.0001 0.001 0.01 0.1
1
10
LOAD CURRENT (A)
1976 TA02
1976f
1