ISL97651ARTZ-TK Intersil, ISL97651ARTZ-TK Datasheet - Page 12

• 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

Some inductors are recommended in Table 3.
Rectifier Diode (Boost Converter)
A high-speed diode is necessary due to the high switching
frequency. Schottky diodes are recommended because of
their fast recovery time and low forward voltage. The reverse
voltage rating of this diode should be higher than the
maximum output voltage. The rectifier diode must meet the
output current and peak inductor current requirements.
Table 4 shows some recommendations for boost converter
diode.
Output Capacitor
The output capacitor supplies the load directly and reduces
the ripple voltage at the output. Output ripple voltage
consists of two components: the voltage drop due to the
inductor ripple current flowing through the ESR of output
capacitor, and the charging and discharging of the output
capacitor.
For low ESR ceramic capacitors, the output ripple is
dominated by the charging and discharging of the output
capacitor. The voltage rating of the output capacitor should
be greater than the maximum output voltage.
Note: Capacitors have a voltage coefficient that makes their
effective capacitance drop as the voltage across then
increases. C
of the capacitor at a particular voltage and not the
manufacturer’s stated value, measured at 0V.
V
INDUCTOR
4.55A
4.6A
5.5A
RIPPLE
MBRS340
TABLE 4. BOOST CONVERTER RECTIFIER DIODE
6.8µH/
5.2µH/
10µH/
DIODE
SS23
SL23
PEAK
PEAK
PEAK
TABLE 3. BOOST INDUCTOR RECOMMENDATION
=
I
12.95x9.4x5.21 Coilcraft
LPK
RECOMMENDATION
DIMENSIONS
OUT
10x10.1x3.8
10x10x5
V
RATING
(mm)
×
30V/2A
40V/3A
30V/2A
R
in Equation 6 assumes the effective value
ESR
/I
AVG
+
V
----------------------- -
O
Sumida
Cooper
Bussmann
VENDOR
V
–
PACKAGE
O
12
V
IN
SMB
SMC
SMB
×
--------------- -
C
OUT
I
DO3316P-682ML
CDR10D48MNNP-100NC
CD1-5R2
O
×
PART NUMBER
Fairchild
Semiconductor
International
Rectifier
Vishay
Semiconductor
--- -
f
1
s
VENDOR
(EQ. 6)
ISL97651
Table 5 shows some selections of output capacitors.
PI Loop Compensation (Boost Converter)
The boost converter of ISL97651 can be compensated by a
RC network connected from CM1 pin to ground. C3 = 4.7nF
and R1 = 10k RC network is used in the demo board. A
higher resistor value can be used to lower the transient
overshoot - however, this may be at the expense of stability
to the loop.
The stability can be examined by repeatedly changing the
load between 100mA and a max level that is likely to be
used in the system being used. The A
examined with an oscilloscope set to AC 100mV/div and the
amount of ringing observed when the load current changes.
Reduce excessive ringing by reducing the value of the
resistor in series with the CM1 pin capacitor.
Boost Converter Feedback Resistors and
Capacitor
An RC network across feedback resistor R5 may be required
to optimize boost stability when A
than 12V. This network reduces the internal voltage
feedback used by the IC. This RC network sets a pole in the
control loop. This pole is set to approximately fp = 10kHz for
C
adding a small capacitor (20pF to 100pF) in parallel with R5
(i.e. R17 = short) may help to reduce A
improve regulation, particularly if high value feedback
resistors are used.
Cascaded MOSFET Application
An 20V N-channel MOSFET is integrated in the boost
regulator. For the applications where the output voltage is
greater than 20V, an external cascaded MOSFET is needed,
as shown in Figure 12. The voltage rating of the external
MOSFET should be greater than A
R17
C18
TABLE 5. BOOST OUTPUT CAPACITOR RECOMMENDATION
OUT
CAPACITOR
10µF/25V
10µF/25V
=
=
= 10µF and fp = 4kHz for C
⎛
⎝
------------------------------------------------------ -
(
2
⎛
⎝
------------------------ -
0.1 R5
×
3.142
1
×
1
×
⎞
⎠
SIZE
1210 TDK
1210 Murata
fp
–
--------- -
R3
×
1
R5
⎞
⎠
–
)
VENDOR
1
VDD
OUT
VDD
C3225X7R1E106M
GRM32DR61E106K
VDD
voltage is set to less
= 30µF. Alternatively,
VDD
.
PART NUMBER
voltage should be
noise and
April 24, 2009
(EQ. 7)
(EQ. 8)
FN7493.3