LT1976B Datasheet, PDF (1/28 Pages) Linear Technology – High Voltage 1.5A, 200kHz Step-Down Switching Regulator with 100μA Quiescent Current

LT1976/LT1976B
High Voltage 1.5A, 200kHz
Step-Down Switching Regulator
with 100μA Quiescent Current
FEATURES
■ _{Wide Input Range: 3.3V to 60V}
■ _{1.5A Peak Switch Current (LT1976)}
■ _{100μA Quiescent Current (LT1976)**}
■ _{1.6mA Quiescent Current (LT1976B)}
■ _{Low Shutdown Current: IQ < 1μA}
■ _{Power Good Flag with Programmable Threshold}
■ _{Load Dump Protection to 60V}
■ _{200kHz Switching Frequency}
■ _{Saturating Switch Design: 0.2Ω On-Resistance}
■ _{Peak Switch Current Maintained Over}
Full Duty Cycle Range*
■ _{1.25V Feedback Reference Voltage}
■ _{Easily Synchronizable}
■ _{Soft-Start Capability}
■ _{Small 16-Pin Thermally Enhanced TSSOP Package}
U
APPLICATIO S
■ _{High Voltage Power Conversion}
■ _{14V and 42V Automotive Systems}
■ _{Industrial Power Systems}
■ _{Distributed Power Systems}
■ _{Battery-Powered Systems}
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Protected by U.S. Patents, including 6498466
**See Burst Mode Operation section for conditions
DESCRIPTIO
The LT^®1976/LT1976B are 200kHz monolithic step-down
switching regulators that accept 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
circuitry. 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. The LT1976B does not shift into Burst Mode
operation at low currents, eliminating low frequency out-
put ripple at the expense of efficiency. 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 devices
also have a power good flag with a programmable thresh-
old and time-out and thermal shutdown protection.
The LT1976/LT1976B are available in a 16-pin TSSOP
package with Exposed Pad leadframe for low thermal
resistance.
TYPICAL APPLICATIO
14V to 3.3V Step-Down Converter with
100μA No Load Quiescent Current
V_IN
3.3V TO 60V
1500pF
10k
4.7μF
100V
CER
330pF
1μF
V_IN BOOST
SHDN
SW
0.33μF 33μH ₄₁₄₈
LT1976 0.1μF
10MQ60N
V_C
C_SS
V_BIAS
FB
47pF
165k
1%
C_T
SYNC ^PGFB
100k
GND
PG
1%
V_OUT
3.3V
1A
100μF
6.3V
TANT
1976 TA01
LT1976 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
LT1976 Efficiency and Power
Loss vs Load Current
100
10
EFFICIENCY
75
5V
3.3V
50
25
1
0.1
TYPICAL
POWER LOSS
0.01
0
0.001
0.1
1
10 100 1000 10000
LOAD CURRENT (mA)
1976 TA02
1976bfg
1