L6917B
PIN FUNCTION
(continued)
N
16
Name
ISEN2
Description
Channel 2 current sense pin. The output current may be sensed across a sense resistor or
across the low-side mosfet Rds
ON.
This pin has to be connected to the low-side mosfet drain or
to the sense resistor through a resistor Rg in order to program the positive current limit at 140%
as follow:
35
µA ⋅
R
g
I
MA X
= --------------------------
R
se nse
Where 35µA is the current offset information relative to the Over Current condition (offset at OC
threshold minus offset at zero load).
The net connecting the pin to the sense point must be routed as close as possible to the
PGNDS2 net in order to couple in common mode any picked-up noise.
17
OSC/
INH/
FAULT
Oscillator switching frequency pin. Connecting an external resistor from this pin to GND, the
external frequency is increased according to the equation:
14.82
⋅
10
f
S
=
300KHz
+ -----------------------------
R
O SC
(
KΩ
)
Connecting a resistor from this pin to Vcc (12V), the switching frequency is reduced according to
the equation:
12.91
⋅
10
f
S
=
300KHz
– -----------------------------
R
O SC
(
KΩ
)
If the pin is not connected, the switching frequency is 300KHz.
Forcing the pin to a voltage lower than 0.8V, the device stop operation and enter the inhibit state.
The pin is forced high when an over or under voltage is detected. This condition is latched; to
recover it is necessary turn off and on VCC.
18-22
VID4-0
Voltage IDentification pins. These input are internally pulled-up and TTL compatible. They are
used to program the output voltage as specified in Table 1 and to set the power good thresholds.
Connect to GND to program a ‘0’ while leave floating to program a ‘1’.
This pin is an open collector output and is pulled low if the output voltage is not within the above
specified thresholds.
If not used may be left floating.
Channel 2 bootstrap capacitor pin. Through this pin is supplied the high side driver and the upper
mosfet. Connect through a capacitor to the PHASE2 pin and through a diode to Vcc (cathode vs.
boot).
7
6
23
PGOOD
24
BOOT2
25
26
27
28
UGATE2 Channel 2 high side gate driver output.
PHASE2 This pin is connected to the source of the upper mosfet and provides the return path for the high
side driver of channel 2.
LGATE2
PGND
Channel 2 low side gate driver output.
Power ground pin. This pin is common to both sections and it must be connected through the
closest path to the low side mosfets source pins in order to reduce the noise injection into the
device.
7/33
STMICROELECTRONICS [ STMICROELECTRONICS ]
