ISL97645AIRZ-T Intersil, ISL97645AIRZ-T Datasheet - Page 14

• Manufacturer Part Number: ISL97645AIRZ-T
• Description: IC REG BOOST VON VCOM 24-QFN
• Manufacturer: Intersil

Specifications of ISL97645AIRZ-T

• Applications: LCD Monitor, Notebook Display
• Current - Supply: 1mA
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Start-Up Sequence
When V
threshold value, Boost converter starts up, and gate pulse
modulator circuit output holds until VDPM is charged to
1.215V. Note that there is a DC path in the boost converter
from the input to the output through the inductor and diode,
hence the input voltage will be seen at output with a forward
voltage drop of diode before the part is enabled. If this
voltage is not desired, the following circuit can be inserted
between input and inductor to disconnect the DC path when
the part is disabled.
.
V
The V
back plate of an LCD display. This plate is capacitively
coupled to the pixel drive voltage which alternately cycles
FIGURE 18. CIRCUIT TO DISCONNECT THE DC PATH OF
COM
TO INDUCTOR
COM
ENABLE
IN
Amplifier
>VLOR
>VLOR
V
exceeds VLOR and ENABLE reaches the VIH
amplifier is designed to control the voltage on the
x
x
x
IN
BOOST CONVERTER
14
<1.215V
<1.215V
>1.215V
VDPM
x
x
TABLE 6. VGH_M STATUS TABLE
RESET
High
High
INPUT
Low
x
x
ISL97645A
positive and negative at the line rate for the display. Thus the
amplifier must be capable of sourcing and sinking capacitive
pulses of current, which can occasionally be quite large (a
few 100mA for typical applications).
The ISL97645A V
400mA. This limit level, which is roughly the same for
sourcing and sinking, is included to maintain reliable
operation of the part. It does not necessarily prevent a large
temperature rise if the current is maintained. (In this case the
whole chip may be shut down by the thermal trip to protect
functionality.) If the display occasionally demands current
pulses higher than this limit, the reservoir capacitor will
provide the excess and the amplifier will top the reservoir
capacitor back up once the pulse has stopped. This will
happen on the µs time scale in practical systems and for
pulses 2 or 3 times the current limit, the V
have settled again before the next line is processed.
Fault Protection
ISL97645A provides the overall fault protections including
over current protection and over-temperature protection.
An internal temperature sensor continuously monitors the
die temperature. In the event that die temperature exceeds
the thermal trip point, the device will shut down and disable
itself. The upper and lower trip points are typically set to
+140°C and +100°C respectively.
<2.5V
>2.5V
>2.5V
>2.5V
>2.5V
VGH
GROUND
GROUND
GROUND
Switching
controlled by
VFLK
VGH
COM
VGH_M
amplifier's output current is limited to
Will be grounded if VIN is above
a logic threshold. Could occur at
power-up or power-down
Start-up only condition: If either
V
VDPM < 1.215V, GND VGHM
Power-down state. Could occur
at power-up if part starts with
VGH > 2.5V
IN
> VLOR or reset is H, but
COMMENT
COM
voltage will
October 21, 2010
FN6353.1