isl97635a Intersil Corporation, isl97635a Datasheet - Page 15

• Manufacturer Part Number: isl97635a
• Description: Smbus 6-channel Led Driver
• Manufacturer: Intersil Corporation

subsequently falls below 20% of the target OVP level, the
input protection FET will also be switched off.
Over-Temperature Protection (OTP)
The ISL97635A includes two over-temperature thresholds.
The lower threshold is set to +130°C. When this threshold is
reached, any channel which is outputting current at a level
significantly below the regulation target will be treated as
“open circuit” and disabled after a time-out period. This
time-out period is also reduced to 800µs when it is above the
lower threshold. The intention of the lower threshold is to
allow bad channels to be isolated and disabled before they
cause enough power dissipation (as a result of other
channels having large voltages across them) to hit the upper
temperature threshold.
REG
VSET/2
VIN
IMAX
DRIVER
15
ILIMIT
REGISTER
FAULT
STATUS
FAULT/
LOGIC
FIGURE 18. SIMPLIFIED FAULT PROTECTIONS
CONTROL
SMBUS
LOGIC
DRIVER
SHORT
THRM
THRM
SHDN
SHDN
FET
O/P
OTP
OTP
PWM/OC0/SC0
ISL97635A
VSET
LX
VSC
VSC
LX
DC CURRENT
+
-
The upper threshold is set to +150°C. Each time this is
reached, the boost will stop switching and the output current
sources will be switched off. Once the device has cooled to
approximately +100°C, the device will restart with the DC
LED current level reduced to 77% of the initial setting. If the
dissipation problem persists, subsequent hitting of the limit
will cause identical behavior, with the current reduced in
steps to 53% and finally 30%. Hitting of the upper threshold
will also set the thermal fault bit of the Fault/Status register
0x02. Unless disabled via the EN pin, the device stays in an
active state throughout, allows the external processor to
interrogate the fault condition.
For the extensive fault protection conditions, please refer to
Figure 18 and Table 1 for details.
OVP
T2
T1
SENSOR
TEMP
REF
VOUT
Q0
PWM/OC5/SC5
IIN0
VSET
+
-
Q5
IIN5
December 22, 2008
FN6564.2