ISL97651ARTZ-TK Intersil, ISL97651ARTZ-TK Datasheet - Page 11

• Manufacturer Part Number: ISL97651ARTZ-TK
• Description: IC LCD SUPPLY HP 4CHN 36-TQFN
• Manufacturer: Intersil

Specifications of ISL97651ARTZ-TK

• Applications: LCD TV/Monitor
• Current - Supply: 400µA
• Voltage - Supply: 4 V ~ 5.5 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 36-TQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Applications Information
The ISL97651 provides a complete power solution for TFT
LCD applications. The system consists of one boost
converter to generate the A
one buck converter to provide voltage to logic circuit in the
LCD panel, one integrated V
linear-regulator controller to provide the voltage to row
drivers. This part also integrates V
help to optimize the picture quality. With the high output
current capability, this part is ideal for big screen LCD TV
and monitor panel application.
The integrated boost converter and buck converter operate
at 1.2MHz which can allow the use of multilayer ceramic
capacitors and low profile inductor which result in low cost,
compact and reliable system. The logic output voltage is
independently enabled to give flexibility to the system
designers.
Boost Converter
The boost converter is a current mode PWM converter
operating at a fixed frequency of 1.2MHz. It can operate in
both discontinuous conduction mode (DCM) at light load and
continuous mode (CCM). In continuous current mode,
current flows continuously in the inductor during the entire
switching cycle in steady state operation. The voltage
conversion ratio in continuous current mode is given by
Equation 1:
Where D is the duty cycle of the switching MOSFET
Figure 11 shows the functional block diagram of the boost
regulator. It uses a summing amplifier architecture consisting
of gm stages for voltage feedback, current feedback and
slope compensation. A comparator looks at the peak
inductor current cycle by cycle and terminates the PWM
cycle if the current limit is reached.
An external resistor divider is required to divide the output
voltage down to the nominal reference voltage. Current
drawn by the resistor network should be limited to maintain
the overall converter efficiency. The maximum value of the
resistor network is limited by the feedback input bias current
and the potential for noise being coupled into the feedback
pin. A resistor network in the order of 60kΩ is recommended.
The boost converter output voltage is determined by
Equation 2:
The current through the MOSFET is limited to a minimum of
4.4A
V
----------------------- -
V
BOOST
BOOST
V
IN
PEAK
=
=
(maximum values can be up to 6.3A
(
------------------------- -
------------ -
1 D
R
–
1
3
R
+
5
R
5
)
×
V
REF
VDD
ON
11
charge pump and one V
voltage for column drivers,
ON
-slice circuit which can
PEAK
.
(EQ. 2)
(EQ. 1)
OFF
ISL97651
This restricts the maximum output current (average) based
on Equation 3:
Where ΔI
by Equation 4:
where f
Table 1 gives typical values (margins are considered 10%,
3%, 20%, 10% and 15% on V
Boost Converter Input Capacitor
An input capacitor is used to suppress the voltage ripple
injected into the boost converter. A ceramic capacitor with
capacitance larger than 10µF is recommended. The voltage
rating of input capacitor should be larger than the maximum
input voltage. Examples of recommended capacitors are
given in Table 2 below.
Boost Inductor
The boost inductor is a critical component which influences
the output voltage ripple, transient response, and efficiency.
Values of 3.3µH to 10µH are to match the internal slope
compensation. The inductor must be able to handle without
saturating the following average and peak current:
I
ΔI
I
I
OMAX
LAVG
LPK
L
TABLE 2. BOOST CONVERTER INPUT CAPACITOR
V
CAPACITOR
TABLE 1. MAXIMUM OUTPUT CURRENT CALCULATION
IN
=
10µF/16V
10µF/10V
22µF/10V
4
4
4
5
5
5
=
V
---------
(V)
=
=
S
L
I
IN
LAVG
------------ -
1 D
L
is the switching frequency (1.2MHz).
⎛
⎝
×
I
I
–
is peak to peak inductor ripple current, and is set
LMT
O
---- -
f
D
RECOMMENDATION
S
+
V
–
ΔI
--------
O
2
ΔI
--------
12
15
12
15
9
9
L
2
(V)
L
SIZE
1206
0805
1210
⎞
⎠
×
V
---------
V
IN
O
L (µH)
VENDOR
Murata
Murata
6.8
6.8
6.8
6.8
6.8
6.8
TDK
IN
, V
O
, L, f
F
C3216X7R1C106M
GRM21BR61A106K
GRB32ER61A226K
S
S
1.2
1.2
1.2
1.2
1.2
1.2
(MHz)
PART NUMBER
and I
OMAX
I
OMAX
April 24, 2009
1661
1173
2077
1466
1099
879
:
(EQ. 5)
FN7493.3
(EQ. 3)
(EQ. 4)
(mA)