LT8709_15 Datasheet, PDF (43/46 Pages) Linear Technology – Negative Input Synchronous Multi-Topology DC/DC Controller

LT8709
Typical Application
400kHz, Negative Buck-Boost Converter Generates a –24V/2.5A Output from a –15V to –30V Input
L1
15.4µH
C_IN
10µF
×4
4.7µF
+ ^220µF
54.9k
10k 2.2µF
100k
–V_IN
–15V TO –30V
88.7k
10µF
2.2Ω
×3
R_{DAMP CDAMP}
C1
10µF
L2
15.4µH
MN
3mΩ
R_SENSE1
–V_IN
BG
CSN CSP TG
GND
ISP
EN/FBIN ^LT8709
ISN
INTV_CC
MODE
PG
RT
SYNC
–V_IN
FBY
BIAS
INTV_EE
V_C
IMON SS
68nF
470nF
D1
R_SENSE2
13m
274k
2.2µF
4.7µF
60.4k
100pF
3.3nF
8709 TA05
V_OUT
–24V
2.5A
C_OUT2
330µF
C_OUT1
10µF
×2
L1, L2: WÜRTH-HCI, 15.4µH, 7443551151
MN: INFINEON, BSC039N06NS
D1: DIODES INC, SBR12U100P5
R_SENSE1: 3mΩ, 2512
R_SENSE2: 13mΩ, 2512
C_IN: 50V, 10µF, X7R, 1210
C1: 50V, 10µF, X7R, 1210
R_DAMP: 2.2Ω, 0805
C_DAMP: 50V, 10µF, X7R, 1210
C_OUT1: 50V, 10µF, X7R, 1210
Efficiency and Power Loss vs
Load Current
100
7
–V_IN = –15V
90
6
80
–V_IN = –24V
–V_IN = –24V
5
70
4
60
3
–V_IN = –15V
50
2
40
1
30
0
0.5
1
1.5
LOAD CURRENT (A)
0
2
2.5
8709 TA05b
Transient Response with 1A to 2.5A to 1A
Output Load Step (–V_IN = –24V)
I_LOAD
2A/DIV
V_OUT
500mV/DIV
AC-COUPLED
I_L1 + I_L2
5A/DIV
500µs/DIV
8709 TA05c
For more information www.linear.com/LT8709
8709f
43