irs20955 International Rectifier Corp., irs20955 Datasheet - Page 10

• Manufacturer Part Number: irs20955
• Description: Protected Digital Audio Driver
• Manufacturer: International Rectifier Corp.

Protection Control
The internal protection control block dictates the
operational mode-normal, or shutdown, using the
input of the CSD pin. The IC functions as expected
in the normal mode. In shutdown mode, the IC
forces LO and HO to output 0 V with respect to
COM and VS to turn off the power MOSFETs.
The CSD pin provides five functions.
Self Reset Protection
By putting a capacitor between CSD and VSS, the
IRS20955S can reset itself after entering shutdown
mode.
www.irf.com
Figure 8. Self Reset Protection Configuration
1. Power up delay timer
2. Self-reset timer
3. Shutdown input
4. Latched protection configuration
5. Shutdown status output (host I/F)
Ct
VDD
CSD
VSS
Ct
VDD
CSD
VREF
OCSET
VSS
NC
IN
DT
Figure 7. Shutdown Functional Block Diagram
CSH
VCC
COM
HO
NC
VB
VS
LO
Vth2
Vth1
COMP1
COMP2
`
`
UVLO(VCC)
LEVEL
SHIFT
HV
OC
S
R
Designing C
The timing capacitor, C
and t
The values chosen for t
the capacitance of C
where I
CSD pin
V
DD
Q
FLOATING INPUT
•
•
= the supply voltage with respect to V
SU
PWM
.
t
from when the IC enters shutdown mode to
the time when the IC resumes operation.
t
heating the MOSFET from the repetitive
sequence of shutting down and resuming
operation during over-current conditions. In
most
recommended time for t
t
up the IC in shutdown mode to the moment
the IC releases shutdown to begin normal
operation.
RESET,
RESET
SU
CSD
is the amount of time between powering
= the charge/discharge current at the
t
DEAD TIME
LEVEL
SHIFT
should be long enough to avoid over
C
is the amount of time that elapses
HV
C
of
SD
t
t
=
=
IRS20955(S)PbF
t
t
applications,
t
`
using the given equations:
RESET
0
1
SU
7 .
LEVEL
SHIFT
1 .
HV
HO
LO
t
, is used to program t
RESET
⋅
⋅
⋅
V
I
V
⋅
CSD
DD
I
DD
CSD
and t
FLOATING HIGH SIDE
OC DET (H)
UVLO(VB)
OC DET (L)
RESET
LOW SIDE
[F]
[F]
SU
the
is 0.1.
will determine
SS.
minimum
10
RESET