SI9978 Datasheet, PDF (5/6 Pages) Vishay Siliconix – Configurable H-Bridge Driver

Si9978
Vishay Siliconix
PIN DESCRIPTION (CONT’D)
Pin 6: MODE
This input determines whether the Si9978 functions as an
H-bridge or as two independent half-bridges. When the MODE
pin is at logic “1”, the Si9978 functions as an H-bridge, and
when MODE is at logic “0”, it functions as two independent
half-bridges.
Pin 7: BRK
When this input and MODE are at logic “1”, both bottom gate
drives are switched high, turning on the bottom MOSFETs.
When this input is at logic “0”, the Si9978 operates normally.
Pin 8: CL/FAULT_B
This is an open drain output which is active low. When the
MODE pin is at logic “1”, this pin functions as CL and indicates
that the H-bridge is in current limit. It stays low for the duration
of the current limit one-shot. With the MODE pin at logic “0”, it
serves as the FAULT output for half-bridge B to indicate when
an undervoltage or overcurrent condition is detected. When
indicating an overcurrent condition, the output stays low for the
duration of the current limit one-shot. The FAULT output resets
automatically when the condition clears.
Pin 9: FAULT/FAULT_A
This is an open drain output which is switched low when an
undervoltage or overcurrent condition is detected. When
indicating an overcurrent condition, the output stays low for the
duration of the current limit one-shot. When the MODE pin is
at logic “1”, this pin is the H-bridge FAULT output. With the
MODE pin at logic “0”, it serves as the FAULT output for
half-bridge A. The FAULT output resets automatically when the
condition clears.
Pin 10: NC
No internal connection.
Pin 11: R_A/C_A
The timing resistor and capacitor for the current limit one-shot
are connected to this pin. The values of the resistor and
capacitor determine the off time set by the one-shot. The
one-shot is triggered when the current limit comparator detects
an overcurrent condition.
Pin 12: R_B/C_B
The timing resistor and capacitor for the current limit one-shot
are connected to this pin. The values of the resistor and
capacitor determine the off time set by the one-shot. The
Document Number: 70011
S-40804—Rev. E, 26-Apr-04
one-shot is triggered when the current limit comparator detects
an overcurrent condition.
Pin 13: IL_A+ and Pin 14, IL_B+
These are the overcurrent sense inputs. Internally, they are
connected to the noninverting inputs of the current limit
comparators. Externally they are connected to the source(s) of
the low-side MOSFET(s) and the current sense resistor.
Pin 15: GND
The GND pin is the ground return for V+ and the ground
reference for the logic. Also, this is the ground reference input
for the current limit comparators and is connected to the
ground side of the internal 100-mV references. This pin should
be connected directly to the ground side of the current sensing
resistors.
Pin 16: GB_B and Pin 20, GB_A
These pins drive the gates of the low-side power MOSFETs.
Pin 17: GT_B and Pin 21, GT_A
These pins drive the gates of the high-side power MOSFETs.
Pin 18: S_B and Pin 22, S_A
These are the source connections of the high-side power
MOSFETs, the drain of the external low-side power MOSFET,
the negative terminal of the bootstrap capacitor, and the output
for each half-bridge.
Pin 19: CAP_B and Pin 23, CAP_A
These are the connections for the positive terminals of the
bootstrap capacitors C_BA and C_BB. A 0.01-mF capacitor can be
used for most applications.
Pin 24: V+
This is the only external power supply required for the Si9978,
and must be the same supply used to power the H-bridge it is
driving. The Si9978 powers the low-voltage logic, low-side
gate driver, and bootstrap/ charge pump circuits from
self-contained voltage regulators which require only a
bootstrap capacitor on the CAP pins.
No voltage sensing circuitry monitors V+ directly; however, the
low-voltage, internally generated supply and the bootstrap
voltage (which are derived from V+) are directly protected by
undervoltage monitors.
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