Linear Technology DC257, Демонстрационное руководство, Страница: 2 / 13

2
DEMO MANUAL DC257
NO-DESIGN SWITCHER
W
ARY A
U
CE SU PERFOR
WW
SYMBOL PARAMETER CONDITIONS JUMPER POSITION VALUE
I
OUT
Minimum Output Current V
IN
= 5V, V
OUT
= 2.5V 600mA
V
IN
= 5V, V
OUT
= 3.3V 500mA
V
IN
= 3V, V
OUT
= 2.5V 300mA
f
OSC
Operating Frequency Unsynchronized All 350kHz
Synchronized All 385kHz to 550kHz
V
RIPPLE
Typical Output Ripple I
OUT
= 500mA, V
IN
= 5V, V
OUT
= 3.3V 30mV
P-P
V
OUT
Typical Load Regulation 0mA < I
OUT
< 0.5A, V
IN
= 5V, V
OUT
= 3.3V 0.5%
V
SYNC
Synchronize Threshold Voltage All 1.2V
V
RUN/SS
Minimum Shutdown Threshold Voltage All 0.4V
V
REF
Reference Output Voltage I
REF
= 0 All 1.19V
I
REF
Maximum V
REF
Output Currrent All 100
µ
A
Figure 1. LTC1707 Constant Frequency, High Efficiency Converter
Note 1: Programmable via optional R6. V
OUT
= 0.8V(1 + 210k/R6)
PACKAGE A D SCHE ATIC DIAGRA S
W U W
1
2
3
4
8
7
6
5
TOP VIEW
V
REF
SYNC/MODE
V
IN
SW
I
TH
RUN/SS
V
FB
GND
S8 PACKAGE
8-LEAD PLASTIC SO
LTC1707CS8
V
FB
GND
I
TH
V
IN
SW
3
4
1
6
5
I
TH
V
REF
RUN/SS
2
8
SYNC/
MODE
7
LTC1707
C
C1
C
SS
0.1
µ
F
C
C2
47pF
R
C
E3
RUN/SS
R2
165k
C
REF
1000pF
+
L1 15
µ
H
C
OUT
100
µ
F
6.3V
+
C
IN
22
µ
F
16V
1.8V
R3
97.6k
2.5V
R1
237k
1.5V
R4
78.7k
R8
10
Ω
JP2
2.9V
R5
66.5k R6*
OPTIONAL
3.3V OPEN
R7
210k
E1
V
REF
E8
SYNC/MODE
E2
V
IN
≤
8.5V
E7
V
OUT
E6
V
OSENSE
E4/E5
GND
DC257 F01
SPACE IS PROVIDED FOR AN OPTIONAL RESISTOR TO PROGRAM A CUSTOM OUTPUT VOLTAGE. THE OUTPUT VOLTAGE MUST NOT EXCEED 3.3V
OPTIONAL
*