LT1776C Linear Technology, LT1776C Datasheet - Page 14

• Manufacturer Part Number: LT1776C
• Description: Wide Input Range/ High Efficiency/ Step-Down Switching Regulator
• Manufacturer: Linear Technology

Minimum Component Count Application
Figure 4a shows a basic “minimum component count”
application. The circuit produces 5V at up to 500mA I
with input voltages in the range of 10V to 40V. The typical
P
SHDN and SYNC pins are unused, however either (or both)
can be optionally driven by external signals as desired.
LT1776
TYPICAL APPLICATIONS
14
OUT
/P
IN
efficiency is shown in Figure 4b. As shown, the
10V TO
40V
V
IN
+
C1: PANASONIC HFQ
C2: AVX D CASE TPSD107M010R0080
C4, C5: X7R OR COG/NPO
D1: MOTOROLA 100V, 1A, SMD SCHOTTKY
L1: COILCRAFT DO3316P-104
U
C1
39 F
63V
Figure 4a. Minimum Component Count Application
C5
100pF
90
80
70
60
50
40
30
20
1
1
6
V
V
V
Figure 4b. P
IN
IN
IN
SHDN
SYNC
= 10V
= 20V
= 30V
LT1776
GND
V
OUT
IN
5
4
V
V
10
V
SW
IN
FB
V
CC
C
I
= 40V
LOAD
OUT
2
3
7
8
User-Programmable Undervoltage Lockout
Figure 5 adds a resistor divider to the basic application.
This is a simple, cost-effective way to add a user-
programmable undervoltage lockout (UVLO) function.
Resistor R5 is chosen to have approximately 200 A
through it at the nominal SHDN pin lockout threshold of
1.25V. The somewhat arbitrary value of 200 A was
/P
(mA)
FOR 3.3V V
R1: 24.3K, R2: 14.7k
L1: 68 H, DO3316P-683
I
IN
OUT
R3
22k
5%
Efficiency
100
: 0mA TO 500mA
D1
MBRS1100
C3
2200pF
X7R
OUT
1776 F04b
VERSION:
100 H
1000
L1
C4
100pF
+
C2
100 F
10V
R1
36.5k
1%
R2
12.1k
1%
1776 F04a
V
5V
0mA to 500mA
OUT