Linear Technology Analog Devices LT8708, Datasheet, Page: 58 / 64

LT8708
58
Rev 0
For more information www.analog.com
APPLICATIONS INFORMATION
Direction Change with
V
BAT1
= 47.5V and V
BAT2
= 14V
Direction Change with
V
BAT1
= 55V and V
BAT2
= 14V
Direction Change with
V
BAT1
= 47.5V and V
BAT2
= 36V
Efficiency V
BAT1
Charging Lead Acid Battery V
BAT2
30ms/DIV
8708 TA04d
DIR
5V/DIV
I
L
20A/DIV
I
IN
10A/DIV
I
OUT
20A/DIV
30ms/DIV
8708 TA04e
DIR
5V/DIV
I
L
20A/DIV
I
OUT
10A/DIV
I
IN
20A/DIV
30ms/DIV
8708 TA04f
DIR
5V/DIV
I
L
20A/DIV
I
IN
5A/DIV
I
OUT
20A/DIV
CHARGIN V
BAT2
CHARGING V
BAT1
VBAT1 (V)
VBAT2 (V)
10 20 30 40 50 60
85
88
91
94
97
100
EFFICIENCY (%)
EFFICIENCY
8708 TA04g
V
BAT2
I
OUT
CHARGING TIME (HOURS)
0 5 10 15
10
11
12
13
14
15
0
3
6
10
13
16
V
BA
T2
(V)
I
OUT
(A)
V
BAT2
8708 TA04h
V
BAT1
Charge Voltage = 48V (FBIN in RHCM) V
BAT2_UV
to Stop Discharging = 10.5V (VOUTLOMON Falling) or 12.3V (VOUTLOMON Rising)
V
BAT2
Charge Voltage = 14.5V (FBOUT in FHCM) V
BAT1
Charging Current Limit = 4A (IMON_INN)
V
BAT1_DEAD
= 21.3V (Falling) or 22.2V (Rising) V
BAT2
Charging Current Limit = 15A (IMON_OP)
V
BAT2_DEAD
= 9.25V (Falling) or 9.4V (Rising) Frequency = 120kHz
Table of Operation Modes and Power Flow Directions
CONDITIONS RESULTS
V
BAT1
V
BAT2
DIR POWER FLOW CHIP OPERATES IN RVSOFF *
<V
BAT1_DEAD
–
–
No Power Flow
Shutdown
–
– <V
BAT2_DEAD
No Switching
<V
BAT1_UV
> V
BAT2_DEAD
Hi FHCM
>V
BAT1_UV
>14.5V
>V
BAT2_DEAD
and <14.5V
Power Flows from V
BAT1
to V
BAT2
(V
BAT2
Charging)
>V
BAT1_DEAD
>V
BAT2_DEAD
and <V
BAT2_UV
Lo
No Power Flow
RHCM
Lo
>48V >V
BAT2_UV
Hi
>V
BAT1_DEAD
and <48V >V
BAT2_UV
Power Flows from V
BAT2
to V
BAT1
(V
BAT1
Charging)
*For use with LT8708-1(s)
48V to 14V Bidirectional Dual Battery System with FHCM & RHCM Details