MAX1747EUP Maxim Integrated Products, MAX1747EUP Datasheet - Page 12

• Manufacturer Part Number: MAX1747EUP
• Description: Charge Pumps
• Manufacturer: Maxim Integrated Products

Specifications of MAX1747EUP

• Function: Step Up, Step Down
• Output Voltage: 4.5 V to 5.5 V, +/- 35 V
• Output Current: 200 mA
• Maximum Operating Temperature: + 85 C
• Package / Case: TSSOP-20
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Triple Charge-Pump TFT LCD
DC-DC Converter
where N is the number of charge-pump stages.
Adjust the main output voltage by connecting a volt-
age-divider from the output (V
Typical Operating Circuit). Adjust the negative low-
power output voltage by connecting a voltage-divider
from the output (V
tive low-power output voltage by connecting a voltage-
divider from the output (V
R2, R4, and R6 in the 10kΩ to 200kΩ range. Calculate
the remaining resistors with the following equations:
where V
5.5V, V
may range from 0 to -35V.
Increasing the flying capacitor’s value increases the
output-current capability. Above a certain point, larger
capacitor values lower the secondary pole formed by
the transfer capacitor and switch R
lizes the output. For the main charge pump, use a
ceramic capacitor based on the following equation:
For the low-power charge pumps, a 0.1µF ceramic
capacitor works well in most applications. Smaller val-
ues may be used for lower current applications.
Component suppliers are listed in Table 1.
For the main charge pump, use a ceramic capacitor
based on the following equation:
For low-frequency applications (close to 200kHz),
selection of the output capacitor is limited solely by the
switching frequency. However, for high-frequency
applications (close to 2MHz), selection of the output
capacitor is limited by the secondary pole formed by
the flying capacitor and switch on-resistance.
12
C
OUT
Efficiency ≅ V
positive low-power charge pump
______________________________________________________________________________________
POS
≥
REF







may range from V
M
= 1.25V. V
20
Hz
R1 = R2 [(V
R3 = R4 [(V
R5 = R6 |V
C
X
POS
×
NEG
≤
C
0 47
X
/ [V
.
) to FBN to REF. Adjust the posi-
Output Voltage Selection
×
OUT
NEG
µ ×
SUPP
f
f
OSC
OUT
POS
OSC
F
POS
/ V
OUT
may range from 4.5V to



SUPP
) to FBP to GND. Select
/ V
MHz
/ V
✕
Output Capacitors
AND
REF
(N+1)] for the
Flying Capacitors
REF
REF
) to FB and GND (see
|
to +35V, and V
ON
) – 1]
) – 1]



2
, which destabi-
µ
F
f
OSC
×
M
Hz







NEG
For the low-power charge pumps, the output capacitor
should be anywhere from 5-times to 20-times larger
than the flying capacitor, depending on the ripple toler-
ance. Increasing the output capacitance or decreasing
the ESR reduces the output ripple voltage and the
peak-to-peak transient voltage.
Using an input capacitor with a value equal to or
greater than the output capacitor is recommended.
Place the capacitor as close to the IC as possible. If the
source impedance or inductance of the input supply is
large, additional input bypassing may be required.
For the low-power charge-pump inputs (SUPN and
SUPP), using bypass capacitors with values equal to or
greater than the flying capacitors is recommended.
Place these capacitors as close to the supply voltage
inputs as possible.
Use Schottky diodes with a current rating greater than
4 times the average output current, and with a voltage
rating of 1.5 times V
and V
The MAX1747 contains an internal current integrator
that improves the DC load regulation but increases the
peak-to-peak transient voltage (see Load-Transient
Waveform in the Typical Operating Characteristics).
Connect a ceramic capacitor between INTG and GND
based on the following equation:
Table 1. Component Suppliers
CAPACITORS
AVX
Kemet
Sanyo
Taiyo Yuden
DIODES
Central
International
Rectifier
Motorola
Nihon
SUPPLIER
SUPN
for the negative charge pump.
C
INTG
≥
SUPP
150
803-946-0690
408-986-0424
619-661-6835
408-573-4150
516-435-1110
310-322-3331
602-303-5454
847-843-7500
Hz
PHONE
for the positive charge pump
f
OSC
×
Integrator Capacitor
C
OUT
Input Capacitors
Rectifier Diodes
803-626-3123
408-986-1442
619-661-1055
408-573-4159
516-435-1824
310-322-3332
602-994-6430
847-843-2798
FAX