Linear Technology Analog Devices LT8708-1 Datasheet page 30

LT8708-1
APPLICATIONS 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 Selection: Connect 17.4k from IMON_OP to
IMON_OP
GND for the LT8708-1.
R Selection: LT8708-1's IMON_ON is only used
IMON_ON
to monitor the I
OUT(SLAVE)
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 , R , R
SENSE1 IMON_INP IMON_INN
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 current in the forward and reverse direc-
IN
tions, respectively.
The maximum slave V current in the forward direction is:
IN
I
(IMON_OP,MASTER)
I =
IN(MAX,FWD,SLAVE)
6A • 12V
= = 9A
8V
30
in the reverse direction. A same
selection: IMON_INP
• V
OUT
V
IN,MIN
For more information
And the maximum slave V
tion is:
I = I
IN(MAX,RVS,SLAVE) IN(IMON_ON,MASTER)
Choose R to be around 17.4k, so that the
IMON_INP
LT8708 1's V
CSPIN–CSNIN
R is calculated to be:
SENSE1
50mV
R = ≅ 6mΩ
SENSE1
9A
Using the equation given in the I
Monitoring and Limiting section of the LT8708 data sheet,
R is recalculated to be:
IMON_INP
R =
IMON_INP
I
IN(MAX, FWD,SLAVE)
And R is calculated to be:
IMON_INN
R =
IMON_INN
I
IN(MAX, RVS,SLAVE)
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.
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current in the reverse direc-
IN
= 3.6A
limit becomes 50mV, and the
and I Current
IN OUT
1.209
Ω ≅ 16.2kΩ
A
• 1m • R + 20µA
SENSE2
V
1.21
Ω ≅ 29.4kΩ
A
• 1m • R + 20µA
SENSE2
V
Rev 0