irs20955 International Rectifier Corp., irs20955 Datasheet - Page 12
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irs20955
Manufacturer Part Number
irs20955
Description
Protected Digital Audio Driver
Manufacturer
International Rectifier Corp.
Datasheet
1.IRS20955.pdf
(21 pages)
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Low-side Over-Current Sensing
For negative load currents, low-side over-current
sensing monitors the load condition and shuts down
switching operation if the load current exceeds the
preset trip level.
Low-side
measurement of V
during low-side turn on. In order to avoid triggering
OCP from overshoot, a blanking interval inserted
after LO turn on disables over-current detection for
450 ns.
The OCSET pin is used to program the threshold for
low-side over-current sensing. When the V
measured across the low-side MOSFET exceeds
the voltage at the OCSET pin with respect COM, the
IRS20955S begins the OCP sequence described
earlier.
www.irf.com
current
LEVEL
SHIFT
DS
HV
sensing
across the low side MOFET
FLOATING HIGH SIDE
5V REG
DEAD TIME
SD
HIGH
Figure 12. Bi-Directional Over-Current Protection
SIDE
CS
is
DETECT
DETECT
UV
UV
based
UV
LEVEL
SHIFT
HV
Q
LOW SIDE CS
on
the
DS
VCC
CSH
HO
VS
LO
COM
OCSET
VB
VREF
Since the voltage from V
the voltage at the OCSET pin, the voltage at OCSET
determines the trip level for over-current detection.
By selecting the trip level for over-current, the
voltage at OCSET can be calculated using the
equation below.
V
In order to minimize the effect of the input bias
current at the OCSET pin, select resistor values for
R4 and R5 such that the current through the voltage
divider is 0.5 mA or more.
* Note: Using V
through a resistive divider provides improved
immunity from fluctuations in V
OCSET
R3
Cbs
R2
= V
R5
R4
R1
DS(LOW SIDE)
Dbs
D1
REF
to generate an input to OCSET
IRS20955(S)PbF
= I
Q2
Q1
TRIP+
S
+B
Vcc
-B
to COM is compared to
x R
CC
DS(ON)
.
OUT
12