ISL97635IRZ-T Intersil, ISL97635IRZ-T Datasheet - Page 15

• Manufacturer Part Number: ISL97635IRZ-T
• Description: IC LED DRVR WHT/RGB BCKLGT 24QFN
• Manufacturer: Intersil
• Type: Backlight, White LED, RGBr

Specifications of ISL97635IRZ-T

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 8
• Internal Driver: Yes
• Type - Primary: Automotive, Backlight
• Type - Secondary: RGB, White LED
• Frequency: 600kHz, 1.2MHz
• Voltage - Supply: 6 V ~ 24 V
• Voltage - Output: 34.5V
• Mounting Type: Surface Mount
• Package / Case: 24-VQFN
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 35mA
• Internal Switch(s): Yes
• Efficiency: 91%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

off. This monitoring happens on a cycle by cycle basis in a
self protecting way.
Additionally, the ISL97635 monitors the voltage at the LX
and OVP pins. At start-up, a fixed current is injected out of
the LX pins and into the output capacitor. The device will not
start-up unless the voltage at LX exceeds 1.2V. Furthermore,
should the voltage at LX not rise above this threshold during
any subsequent period where the power FET is not switched
on, it will immediately disable the input protection FET. The
OVP pin is also monitored such that if it rises above and
subsequently falls below 20% of the target OVP level, the
input protection FET will also be switched off.
Over-Temperature Protection (OTP)
The ISL97635 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
STATUS
FAULT/
FAULT
LOGIC
FIGURE 18. SIMPLIFIED FAULT PROTECTIONS
CONTROL
SMBUS
LOGIC
DRIVER
SHORT
FET
O/P
THRM
THRM
SHDN
SHDN
OTP
OTP
PWM/OC0/SC0
ISL97635
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/OC7/SC7
IIN0
VSET
+
-
Q5
IIN7
December 22, 2008
FN6434.2