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Linear Technology Electronic Components Datasheet

LT1976B Datasheet

Step-Down Switching Regulator

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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 CSS 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
VIN
3.3V TO 60V
1500pF
10k
4.7μF
100V
CER
330pF
1μF
VIN BOOST
SHDN
SW
0.33μF 33μH 4148
LT1976 0.1μF
10MQ60N
VC CSS
CT
SYNC
GND
VBIAS
FB
PGFB
PG
47pF
165k
1%
100k
1%
VOUT
3.3V
1A
100μF
6.3V
TANT
1976 TA01
LT1976 Supply Current vs
Input Voltage
150
VOUT = 3.3V
TA = 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
TYPICAL
POWER LOSS
0.1
0.01
0 0.001
0.1 1 10 100 1000 10000
LOAD CURRENT (mA)
1976 TA02
1976bfg
1


Linear Technology Electronic Components Datasheet

LT1976B Datasheet

Step-Down Switching Regulator

No Preview Available !

LT1976/LT1976B
ABSOLUTE AXI U RATI GS
(Note 1)
VIN, SHDN, PG, BIAS .............................................. 60V
BOOST Pin Above SW ............................................ 35V
BOOST Pin Voltage ................................................. 68V
SYNC, CSS, PGFB, FB ................................................ 6V
Operating JunctionTemperature Range
LT1976EFE/LT1976BEFE (Note 2) ... – 40°C to 125°C
LT1976IFE/LT1976BIFE (Note 2) ..... – 40°C to 125°C
LT1976HFE (Note 2) ........................ – 40°C to 140°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
NC 1
SW 2
NC 3
VIN 4
NC 5
BOOST 6
CT 7
GND 8
16 PG
15 SHDN
14 SYNC
13 PGFB
17
12 FB
11 VC
10 BIAS
9 CSS
FE PACKAGE
16-LEAD PLASTIC TSSOP
θJA = 45°C/W, θJC(PAD) = 10°C/W
EXPOSED PAD IS GND (PIN 17)
MUST BE SOLDERED TO GND (PIN 8)
ORDER PART
NUMBER
LT1976EFE
LT1976IFE
LT1976HFE
LT1976BEFE
LT1976BIFE
FE PART MARKING
1976EFE
1976IFE
1976HFE
1976BEFE
1976BIFE
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full –40°C to 125°C
operating temperature range, otherwise specifications are at TJ = 25°C. VIN = 12V, SHDN = 12V, BOOST = 15.3V, BIAS = 5V,
FB/PGFB = 1.25V, CSS/SYNC = 0V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
VSHDN
ISHDN
SHDN Threshold
SHDN Input Current
Minimum Input Voltage (Note 3)
SHDN = 12V
1.2 1.3 1.4
5 20
2.4 3
V
μA
V
IVINS Supply Shutdown Current
SHDN = 0V, BOOST = 0V, FB/PGFB = 0V
Supply Sleep Current (Note 4) (LT1976) BIAS = 0V, FB = 1.35V
FB = 1.35V
0.1 2
170 230
45 75
μA
μA
μA
IVIN Supply Quiescent Current
Minimum BIAS Voltage (Note 5)
BIAS = 0V, FB = 1.15V, VC = 0.8V (VC = 0V LT1976B)
BIAS = 5V, FB = 1.15V, VC = 0.8V (VC = 0V LT1976B)
3.2 4.10
2.6 3.25
2.7 3
mA
mA
V
IBIASS
IBIAS
VREF
IFB
BIAS Sleep Current (Note 4) (LT1976)
BIAS Quiescent Current
Minimum Boost Voltage (Note 6)
Input Boost Current (Note 7)
Reference Voltage (VREF)
FB Input Bias Current
EA Voltage Gain (Note 8)
SYNC = 3.3V
ISW = 1.5A
ISW = 1.5A
3.3V < VVIN < 60V
110 180
700 800
1.8 2.5
40 50
1.225 1.25 1.275
75 200
900
μA
μA
V
mA
V
nA
V/V
EA Voltage gm
EA Source Current
dI(VC)= ±10μA
FB = 1.15V
400 650 800 μMho
20 40 55
μA
EA Sink Current
FB = 1.35V
15 30 40
μA
VC to SW gm
VC High Clamp
VC Switching Threshold (LT1976B)
3
2.1 2.2 2.4
0.1 0.4 0.8
A/V
V
V
1976bfg
2


Part Number LT1976B
Description Step-Down Switching Regulator
Maker Linear
PDF Download

LT1976B Datasheet PDF






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