ISL97644IRZ-TK Intersil, ISL97644IRZ-TK Datasheet - Page 13

• Manufacturer Part Number: ISL97644IRZ-TK
• Description: IC REG BOOST LDO VON VCOM 24-QFN
• Manufacturer: Intersil

Specifications of ISL97644IRZ-TK

• Applications: LCD Monitor, Notebook Display
• Current - Supply: 1mA
• Voltage - Supply: 3 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

VGH_M
Low to high transition is determined primarily by the switch
resistance and the external capacitive load. High to low
transition is more complex. Take the case where the block is
already enabled (VDPM is H). When VFLK is H, pin CE is
grounded. On the falling edge of VFLK, a current is passed
into pin CE, to charge an external capacitor to 1.2V. This
creates a delay, equal to CE*4200. At this point, the output
begins to pull down from VGH to VDD1. The slew current is
equal to 300/(RE+5000)*Load Capacitance.
VDPM
Start-Up Sequence
Figure 18 shows a detailed start up sequence waveform.
When V
threshold value, Boost converter and LDO start up, and gate
pulse modulator circuit output holds until VDPM goes to
high. 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
VFLK
V
ENABLE
VDPM
IN
FIGURE 17. GATE PULSE MODULATOR TIMING DIAGRAM
0
0
0
0
0
0
0
IN
AVDD
exceeds 2.5V and ENABLE reaches the VIH
FIGURE 18. START-UP SEQUENCE
LDO OUTPUT
13
DELAY TIME
CONTROLLED BY CE
VIN THRESHOLD
SLOPE CONTROLLED
BY RE AND LOAD
CAPACITANCE
VGH_M
VDD_1
VGH
ISL97644
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
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 ISL97644 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
ISL97644 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.
FIGURE 19. CIRCUIT TO DISCONNECT THE DC PATH OF
TO INDUCTOR
COM
COM
ENABLE
Amplifier
amplifier is designed to control the voltage on the
BOOST CONVERTER
COM
amplifier's output current is limited to
COM
voltage will
December 14, 2007
INPUT
FN9228.1