LT1376CS Linear Technology, LT1376CS Datasheet - Page 8

• Manufacturer Part Number: LT1376CS
• Description: IC SW REG 1.5A ADJ STP-DWN16SOIC
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LT1376CS

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 2.42 ~ 21.5 V
• Current - Output: 1.5A
• Frequency - Switching: 500kHz
• Voltage - Input: 5 ~ 25 V
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

LT1375/LT1376
connected to an external voltage higher than 3V, bias
power will be drawn from the external source (typically the
regulated output voltage). This will improve efficiency if
the BIAS pin voltage is lower than regulator input voltage.
High switch efficiency is attained by using the BOOST pin
to provide a voltage to the switch driver which is higher
APPLICATIONS
BLOCK
FEEDBACK PIN FUNCTIONS
The feedback (FB) pin on the LT1376 is used to set output
voltage and also to provide several overload protection
features. The first part of this section deals with selecting
resistors to set output voltage and the remaining part talks
about foldback frequency and current limiting created by
the FB pin. Please read both parts before committing to a
final design. The fixed 5V LT1376-5 has internal divider
8
INPUT
SHDN
SYNC
DIAGRAM
BIAS
COMPARATOR
SHUTDOWN
U
REGULATOR
+
2.9V BIAS
INFORMATION
2.38V
U
W
3.5µA
+
–
0.37V
–
LOCKOUT
COMPARATOR
W
OSCILLATOR
SLOPE COMP
INTERNAL
V
CC
500kHz
U
+
Figure 1. Block Diagram
0.05Ω
Σ
V
FOLDBACK
0.9V
–
CURRENT
C
–
+
CLAMP
LIMIT
CURRENT
SENSE
AMPLIFIER
VOLTAGE GAIN = 10
CURRENT
COMPARATOR
Q2
than the input voltage, allowing switch to be saturated.
This boosted voltage is generated with an external capaci-
tor and diode. Two comparators are connected to the
shutdown pin. One has a 2.38V threshold for undervoltage
lockout and the second has a 0.4V threshold for complete
shutdown.
resistors and the FB pin is renamed SENSE, connected
directly to the output.
The suggested value for the output divider resistor (see
Figure 2) from FB to ground (R2) is 5k or less, and a
formula for R1 is shown below. The output voltage error
caused by ignoring the input bias current on the FB pin is
less than 0.25% with R2 = 5k. A table of standard 1%
values is shown in Table 1 for common output voltages.
S
R
g
SHIFT CIRCUIT
m
FREQUENCY
FLIP-FLOP
= 2000µMho
AMPLIFIER
R
S
ERROR
–
+
CIRCUITRY
DRIVER
2.42V
BOOST
Q1
POWER
SWITCH
1375/76 BD
GND
V
FB
SW
13756fd