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LT1977 Datasheet(PDF) 1 Page - Linear Technology

Part No. LT1977
Description  High Voltage 1.5A, 500kHz Step-Down Switching Regulator with 100uA Quiescent Current
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Maker  LINER [Linear Technology]
Homepage  http://www.linear.com
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LT1977 Datasheet(HTML) 1 Page - Linear Technology

 
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LT1977
1
1977f
High Voltage Power Conversion
14V and 42V Automotive Systems
Industrial Power Systems
Distributed Power Systems
Battery-Powered Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
Wide Input Range: 3.3V to 60V
1.5A Peak Switch Current
Burst Mode
® Operation: 100µA Quiescent Current**
Low Shutdown Current: IQ < 1µA
Power Good Flag with Programmable Threshold
Load Dump Protection to 60V
500kHz 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
High Voltage 1.5A, 500kHz
Step-Down Switching Regulator
with 100µA Quiescent Current
Burst Mode is a registered trademark of Linear Technology Corporation.
*U.S. Patent 6,498,466 and 6,531,909 **See Burst Mode Operation section for conditions
The LT
®1977 is a 500kHz 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 CSS 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 LT1977 is available in a 16-pin TSSOP package with
exposed pad leadframe for low thermal resistance. The
LT1976, a 200kHz reduced switch frequency version of the
LT1977, is also available. See the Applications Information
section for selection criteria between the LT1976 and
LT1977.
VIN
SHDN
BOOST
LT1977
2.2µF
100V
CER
330pF
0.1µF
0.1µF
10µH
1N4148
1µF
SYNC
CT
GND
100µF
6.3V
TANT
VOUT
3.3V
1A
VIN
10MQ100N
1500pF
26k
165k
1%
100k
1%
1977 TA01
10pF
SW
CSS
VC
+
VBIAS
FB
PGFB
PG
14V to 3.3V Step-Down Converter with
100µA No Load Quiescent Current
Efficiency and Power Loss
vs Load Current
LOAD CURRENT (A)
0.0001
0
25
0.001
0.01
0.1
1
1977 TA02
75
100
50
0.001
0.01
1
10
0.1
10
VIN = 12V
3.3V
5V
EFFICIENCY
TYPICAL
POWER LOSS
Supply Current vs Input Voltage
INPUT VOLTAGE (V)
0
0
50
100
10
20
30
40
1977 F05
50
150
25
75
125
60
VOUT = 3.3V
TA = 25°C
DESCRIPTIO
FEATURES
APPLICATIO S
TYPICAL APPLICATIO


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