ISL97653AIRZ-TK Intersil, ISL97653AIRZ-TK Datasheet - Page 14

• 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

Output Capacitor (Buck Converter)
Four 10µF or two 22µF ceramic capacitors are recommended
for this part. The overshoot and undershoot will be reduced
with more capacitance, but the recovery time will be longer.
PI Loop Compensation (Buck Converter)
The buck converter of ISL97653A can be compensated by a
RC network connected from CM2 pin to ground. C
and R
larger value resistor can lower the transient overshoot,
however, at the expense of stability of the loop.
The stability can be optimized in a similar manner to that
described in “PI Loop Compensation (Boost Converter)” on
page 12.
Bootstrap Capacitor (C
This capacitor provides the supply to the high driver circuitry
for the buck MOSFET. The bootstrap supply is formed by an
internal diode and capacitor combination. A 1µF is
recommended for ISL97653A. A low value capacitor can
lead to overcharging and in turn damage the part.
During very light loads, the on-time of the low side diode
may be insufficient to replenish the bootstrap capacitor
voltage. Additionally, if V
MOSFET pull-up device may be unable to turn-on until
V
this case. The minimum load can be adjusted by the
feedback resistors to FBL.
Charge Pump Controllers (V
The ISL97653A includes 2 independent charge pumps (see
charge pump block and connection diagram). The negative
charge pump inverts the SUPN voltage and provides a
regulated negative output voltage. The positive charge pump
doubles or triples the SUPP voltage and provides a
regulated positive output voltage. The regulation of both the
negative and positive charge pumps is controlled by internal
comparators that sense the output voltage. These sensed
voltages are then compared to scaled internal reference
voltages.
Charge pumps use pulse width modulation to adjust the
pump period, depending on the load present. The pumps
can provide 100mA for V
CAPACITOR
LOGIC
TABLE 9. BUCK OUTPUT CAPACITOR RECOMMENDATION
100µF/6.3V
10µF/6.3V
10µF/6.3V
22µF/6.3V
20
falls. Hence, there is a minimum load requirement in
= 10k RC network is used in the demo board. A
SIZE
0805
0805
1210
1206
IN
OFF
- V
13
TDK
Murata
TDK
Murata
14
VENDOR
and 40mA for V
BUCK
)
ON
< 1.5V, the internal
and V
C2012X5R0J106M
GRM21BR60J106K
C3216X5R0J226M
GRM31CR60J107M
PART NUMBER
OFF
ON
.
)
8
= 4.7nF
ISL97653A
Positive Charge Pump Design Consideration
All positive charge pump diodes (D1, D2 and D3 shown in
the “NEGATIVE CHARGE PUMP BLOCK DIAGRAM” on
page 16) for x2 (doubler) and x3 (Tripler) modes of operation
are included in the ISL97653A. During the chip start-up
sequence the mode of operation is automatically detected
when the charge pump is enabled. With both C
present, the x3 mode of operation is detected. With C
present, C
of operation will be detected.
Internal switches M1, M2 and M3 isolate P
until the charge pump is enabled. This is important for TFT
applications that require the negative charge pump output
(V
The maximum P
from the following equations assuming a 50% switching
duty:
Note: V
function of I
I
2 V
------------------------------------------------------------------------------------------------------------------------- - 0.95A
I
3 V
------------------------------------------------------------------------------------------------------------------------- - 0.95V
MAX
MAX
•
•
OFF
SUPP
SUP
(
(
2x
3x
) and A
DIODE
·
)
(
)
P
2
∼
(
∼
8
2
–
–
•
min of 40mA or
min of 40mA or
MAX
2
•
3
(
open and with C
3 R
VDD
(
•
•
2 R
•
(2 • I
V
V
•
OUT
DIODE
DIODE
and V
ONH
supplies to be established prior to P
ONH
MAX
charge pump current can be estimated
+
DIODE
(
(
2 I
+
2 I
2 R
) is the on-chip diode voltage as a
•
R
•
•
ONL
MAX
MAX
ONL
1
+ shorted to C
(40mA) < 0.7V.
)
) V V
)
) V V
)
–
–
)
(
(
ON
ON
)
)
•
•
OUT
2
+, the x2 mode
7
September 7, 2010
from SUPP
and C
(EQ. 14)
7
FN6367.3
OUT
8
.