LT8708-1
30
Rev 0
For more information
MODE Pin: Connect the MODE pin to GND for CCM
operation.
SWEN and
RVSOFF
Pins: Connect the SWEN and
RVSOFF
pins together for the LT8708 and LT8708-1, respectively.
This synchronizes the start-up and operation mode
between the two chips.
ICP and ICN Pins: Connect two 17.4k resistors from the
ICP and ICN pins to GND, respectively. Place them next
to the LT8708 chip and route the ICP and ICN traces to
the LT8708-1’s counterparts, respectively.
R
IMON_OP
Selection: Connect 17.4k from IMON_OP to
GND for the LT8708-1.
R
IMON_ON
Selection: LT8708-1’s IMON_ON is only used
to monitor the I
OUT(SLAVE)
in the reverse direction. A same
value resistor of 24.9k from the LT8708 design example
is selected here to provide an IMON_ON reading on the
same scale as the one on the LT8708.
R
SENSE1
, R
IMON_INP
, R
IMON_INN
selection: IMON_INP
and IMON_INN are used to provide current limits for the
LT8708-1 only. They are set to be equal to the maximum
per phase V
IN
current in the forward and reverse direc-
tions, respectively.
The maximum slave V
IN
current in the forward direction is:
I
IN(MAX,FWD,SLAVE)
=
I
(IMON_OP,MASTER)
• V
OUT
V
IN,MIN
=
6A • 12V
8V
= 9A
And the maximum slave V
IN
current in the reverse direc-
tion is:
I
IN(MAX,RVS,SLAVE)
= I
IN(IMON_ON,MASTER)
= 3.6A
Choose R
IMON_INP
to be around 17.4k, so that the
LT8708 1’s V
CSPIN–CSNIN
limit becomes 50mV, and the
R
SENSE1
is calculated to be:
R
SENSE1
=
50mV
9A
≅
6mΩ
Using the equation given in the I
IN
and I
OUT
Current
Monitoring and Limiting section of the LT8708 data sheet,
R
IMON_INP
is recalculated to be:
R
IMON_INP
=
1.209
I
IN(MAX, FWD,SLAVE)
• 1m
A
V
• R
SENSE2
+ 20µA
Ω
≅
16.2kΩ
And R
IMON_INN
is calculated to be:
R
IMON_INN
=
1.21
I
IN(MAX, RVS,SLAVE)
• 1m
A
V
• R
SENSE2
+ 20µA
Ω
≅
29.4kΩ
FBOUT Pin: Connect FBOUT pin to GND to disable the
FBOUT pin.
FBIN Pin: Connect FBIN pin to LDO33 of the LT8708-1 to
disable the FBIN pin.
APPLICATIONS INFORMATION
