LTC1871 Datasheet, PDF (33/36 Pages) Linear Technology – Wide Input Range, No RSENSE Current Mode Boost, Flyback and SEPIC Controller

LTC1871
TYPICAL APPLICATIO S
4.5V to 28V Input, 5V/2A Output SEPIC Converter with Undervoltage Lockout and Soft-Start
R2
54.9k
1%
C1
4.7nF
R_C
12k
C_C1
8.2nF
C_C2
47pF
R1
115k
1%
R4
49.9k
R3 ^1%
154k
1%
1
RUN
2
I_TH
10
SENSE
9
V_IN
LTC1871
3
FB
4
FREQ
8
INTV_CC
7
GATE
R_T
5
MODE/SYNC
6
GND
162k
1%
C_VCC
4.7µF
10V
X5R
•
C_DC
L1* ^2.2µF
25V
V_IN
4.5V to 28V
X5R
×3 _D1
V_OUT
5V
2A
+ _COUT1
(3A TO 4A PEAK)
330µF
6.3V
C_OUT2
M1
L2*
22µF
C_IN1
2.2µF
+
35V
C_IN2
22µF
•
6.3V
X5R
X5R
35V
GND
1871 TA02a
R5
C2
100Ω
1µF
Q1
X5R
R6
750Ω
NOTES:
1.
V_IN
V_IN
UVLO⁺
UVLO^–
=
=
4.17V
3.86V
2. SOFT-START dV_OUT/dt = 5V/6ms
C_IN1, C_DC: TAIYO YUDEN GMK325BJ225MN
C_IN2: AVX TPSE226M035R0300
C_OUT1: SANYO 6TPB330M
C_OUT2: TAIYO YUDEN JMK325BJ226MN
C_VCC: LMK316BJ475ML
D1: INTERNATIONAL RECTIFIER 30BQ040
L1, L2: BH ELECTRONICS BH510-1007 (*COUPLED INDUCTORS)
M1: SILICONIX/VISHAY Si4840
Q1: PHILIPS BC847BF
Soft-Start
Load Step Response at V_IN = 4.5V
V_OUT
1V/DIV
V_OUT
100mV/DIV
(AC)
I_OUT ^2.2A
1A/DIV
(DC)
0.5A
1ms/DIV
1871 TA02b
Load Step Response at V_IN = 28V
V_OUT
100mV/DIV
(AC)
250µs/DIV
1871 TA02c
I_OUT ^2.2A
1A/DIV
(DC) _0.5A
250µs/DIV
1871 TA02d
33