ISL97653AIRZ-TK Intersil, ISL97653AIRZ-TK Datasheet - Page 11

• Manufacturer Part Number: ISL97653AIRZ-TK
• Description: IC LCD SUPPLY 5CHN 40-QFN
• Manufacturer: Intersil

Specifications of ISL97653AIRZ-TK

• Applications: LCD TV/Monitor
• Current - Supply: 4mA
• Voltage - Supply: 4 V ~ 14 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 40-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application Information
A
The
boost FET. The regulator uses a current mode PI control
scheme which provides good line regulation and good
transient response. It can operate in both discontinuous
conduction mode (DCM) at light loads 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.
The boost soft-start function is digitally controlled within a
fixed 10ms time frame during which the current limit is
increased in eight linear steps.
The boost converter uses a summing amplifier architecture
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 triggered. Since this comparison is cycle
based, the PWM output will be released after the peak
current goes below the current limit threshold.
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:
where R
page 5. Unless otherwise stated, component variables
referred to in equations refer to the Typical Application
Diagram.
The current through the MOSFET is limited to 4.4A peak.
This restricts the maximum output current (average) based
on Equation 3:
Where ΔIL is peak to peak inductor ripple current, and is set
by Equation 4. f
ΔI
V
----------------- -
A
I
OMAX
boost
VDD
V
VDD
L
IN
=
A
VDD
V
---------
=
Boost Converter
L
=
=
IN
3
R
-------------------- -
------------ -
1 D
⎛
⎝
and R
×
boost converter features a fully integrated 4.4A
3
I
R
LMT
–
1
---- -
f
+
D
S
4
R
4
–
s
4
×
ΔI
--------
is the switching frequency (680kHz).
are in the “Typical Application Diagram” on
2
V
L
FBB
⎞
⎠
×
V
---------
V
IN
O
11
(EQ. 1)
(EQ. 2)
(EQ. 3)
(EQ. 4)
ISL97653A
Table 1 gives typical values (worst case margins are
considered 10%, 3%, 20%, 10% and 15% on V
F
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. Some capacitors are recommended in Table 2
for input capacitor.
Boost Inductor
The boost inductor is a critical part which influences the
output voltage ripple, transient response, and efficiency.
Values of 3.3µH to 10µH are recommended to match the
internal slope compensation as well as to maintain a good
transient response performance. The inductor must be able
to handle the average and peak currents expressed in
Equations 5 and 6:
Some inductors are recommended in Table 3.
I
I
INDUCTOR
CAPACITOR
LAVG
LPK
SW
5.1A
6A
10µF/25V
10µF/25V
TABLE 2. BOOST CONVERTER INPUT CAPACITOR
5.9µH/
TABLE 1. MAXIMUM OUTPUT CURRENT CALCULATION
10µH/
PEAK
and I
=
V
PEAK
(V)
12
12
5
5
5
IN
=
TABLE 3. BOOST INDUCTOR RECOMMENDATION
I
LAVG
------------ -
1 D
OMAX
I
–
O
RECOMMENDATION
DIMENSIONS
12.9X12.9X4 Sumida
+
13x13x4.5
ΔI
--------
SIZE
1210
1210
):
(mm)
2
L
V
(V)
12
15
15
18
9
O
TDK
Murata
VENDOR
VENDOR
TDK
(µH)
6.8
6.8
6.8
6.8
6.8
L
RLF12545T-100M5R1
CDEP12D38NP-5R9MB-120
C3225X7R1E106M
GRM32DR61E106K
PART NUMBER
PART NUMBER
IN
September 7, 2010
I
, V
OMAX
(mA)
2215
1673
1344
3254
2670
O
, L,
FN6367.3
(EQ. 5)
(EQ. 6)