LT1375/LT1376
1.5A, 500kHz Step-Down
Switching Regulators
FEATURES
Constant 500kHz Switching Frequency is current mode for fast transient response and good loop
Uses All Surface Mount Components stability. Both fixed output voltage and adjustable parts are
Inductor Size Reduced to 5H available.
Easily Synchronizable
A special high speed bipolar process and new design
Saturating Switch Design: 0.4
techniques achieve high efficiency at high switching fre-
Effective Supply Current: 2.5mA
quency. Efficiency is maintained over a wide output cur-
Shutdown Current: 20A
rent range by using the output to bias the circuitry and by
Cycle-by-Cycle Current Limiting
utilizing a supply boost capacitor to saturate the power
U switch. A shutdown signal will reduce supply current to
APPLICATIO S
20A on both parts. The LT1375 can be externally syn-
chronized from 580kHz to 900kHz with logic level inputs.
Portable Computers
The LT1375/LT1376 fit into standard 8-pin PDIP and SO
Battery-Powered Systems
packages, as well as a fused lead 16-pin SO with much
Battery Charger
lower thermal resistance. Full cycle-by-cycle short-cir-
Distributed Power
cuit protection and thermal shutdown are provided.
Standard surface mount external parts are used, includ-
DESCRIPTIO
ing the inductor and capacitors.
The LT 1375/LT1376 are 500kHz monolithic buck mode
For low input voltage applications with 3.3V output, see
switching regulators. A 1.5A switch is included on the die
LT1507. This is a functionally identical part that can
along with all the necessary oscillator, control and logic
operate with input voltages between 4.5V and 12V.
circuitry. High switching frequency allows a considerable
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
reduction in the size of external components. The topology
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
5V Buck Converter
Efficiency vs Load Current
D2
100
1N914
V = 5V
OUT
V = 10V
IN
C2 90 L = 10H
0.1F
BOOST
OUTPUT**
INPUT
V
V SW
IN 5V, 1.25A
6V TO 25V
80
L1**
C3* +
LT1376-5 BIAS
5H
10F TO
DEFAULT
50F
SHDN
FB
70
= ON
GND V C1
C
+
100F, 10V
D2
C
SOLID
C 1N5818
60
3.3nF
TANTALUM
50
* RIPPLE CURRENT I /2
OUT
0 0.25 0.50 0.75 1.00 1.25
** INCREASE L1 TO 10H FOR LOAD CURRENTS ABOVE 0.6A AND TO 20H ABOVE 1A
LOAD CURRENT (A)
FOR INPUT VOLTAGE BELOW 7.5V, SOME RESTRICTIONS MAY APPLY.
1375/76 TA01
SEE APPLICATIONS INFORMATION.
1375/76 TA02
13756fd
1
EFFICIENCY (%)
U
ULT1375/LT1376
ABSOLUTE MAXIMUM RATINGS (Note 1)
FB Pin Current (Adjustable Part) ............................ 1mA
Input Voltage
Sense Voltage (Fixed 5V Part) .................................. 7V
LT1375/LT1376 .................................................. 25V
SYNC Pin Voltage ..................................................... 7V
LT1375HV/LT1376HV ........................................ 30V
Operating Junction Temperature Range
BOOST Pin Voltage
LT1375C/LT1376C ............................... 0C to 125 C
LT1375/LT1376 .................................................. 35V
LT1375I/LT1376I............................. 40C to 125C
LT1375HV/LT1376HV ........................................ 40V
Storage Temperature Range ................ 65C to 150C
SHDN Pin Voltage ..................................................... 7V
Lead Temperature (Soldering, 10 sec)................. 300C
BIAS Pin Voltage ...................................................... 7V
FB Pin Voltage (Adjustable Part) ............................ 3.5V
PACKAGE/ORDER INFORMATION
TOP VIEW TOP VIEW
TOP VIEW
BOOST 1 8 V BOOST 1 8 V
C GND 1 16 GND
C
V 2 7 FB/SENSE
V 2 7 FB/SENSE NC 2 15 NC
IN IN
V 3 6 GND V GND BOOST 3 14 V
SW 3 6 C
SW
SHDN SYNC V 4 13 FB/SENSE
4 5 BIAS 4 5 SHDN IN
V 5 12 GND
SW
S8 PACKAGE
N8 PACKAGE N8 PACKAGE S8 PACKAGE
8-LEAD PLASTIC SO BIAS 6 11 SHDN
8-LEAD PDIP 8-LEAD PDIP 8-LEAD PLASTIC SO
= 100C/ W (N8) = 100C/ W (N8)
NC 7 10 NC
JA JA
= 120C/ W TO 150C/W DEPENDING ON = 120C/ W TO 150C/W DEPENDING ON
JA JA
GND 8 9 GND
PC BOARD LAYOUT (S8) PC BOARD LAYOUT (S8)
S PACKAGE
ORDER PART S8 PART ORDER PART S8 PART 16-LEAD PLASTIC NARROW SO
NUMBER MARKING NUMBER MARKING
=50C/ W WITH FUSED CORNER PINS
JA
CONNECTED TO GROUND PLANE OR LARGE
LANDS
LT1375CN8 LT1376CN8
LT1375CN8-5 LT1376CN8-5
ORDER PART NUMBER
LT1375IN8 LT1376IN8
LT1375IN8-5 LT1376IN8-5
LT1376CS
LT1375CS8 1375 LT1376CS8 1376
LT1376IS
LT1375CS8-5 13755 LT1376CS8-5 13765
LT1376HVCS
LT1375HVCS8 1375HV LT1376HVCS8 1376HV
LT1376HVIS
LT1375IS8 1375I LT1376IS8 1376I
LT1375IS8-5 1375I5 LT1376IS8-5 1376I5
LT1375HVIS8 375HVI LT1376HVIS8 376HVI
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: