ICL7660CPA Maxim Integrated Products, ICL7660CPA Datasheet - Page 9

• Manufacturer Part Number: ICL7660CPA
• Description: Charge Pumps Switched-Capacitor Voltage Converter
• Manufacturer: Maxim Integrated Products

Specifications of ICL7660CPA

• Function: Inverting, Step Up
• Output Voltage: - 1.5 V to - 10 V, 3 V to 20 V
• Output Current: 20 mA
• Maximum Operating Temperature: + 70 C
• Package / Case: PDIP-8 Narrow
• Minimum Operating Temperature: 0 C
• Mounting Style: Through Hole

The first term is the effective resistance from the
switched-capacitor circuit.
Conversion losses occur during the transfer of charge
between capacitors C1 and C2 when there is a voltage
difference between them. The power loss is:
Efficiency can be improved by lowering output voltage
ripple and output impedance. Both output voltage rip-
ple and output impedance can be reduced by using
large capacitors with low ESR.
The output voltage ripple can be calculated by noting
that the output current is supplied solely from capacitor
C2 during one-half of the charge-pump cycle.
Slowing the oscillator frequency reduces quiescent cur-
rent. The oscillator frequency can be reduced by con-
necting a capacitor to the OSC pin.
Reducing the oscillator frequency increases the ripple
voltage in the MAX1044/ICL7660. Compensate by
increasing the values of the bucket and reservoir
capacitors. For example, in a negative voltage converter,
the pump frequency is around 4kHz or 5kHz. With the
recommended 10µF bucket and reservoir capacitors,
the circuit consumes about 70µA of quiescent current
while providing 20mA of output current. Setting the
Figure 8. Negative Voltage Converter with BOOST and LV
Connections
10µF
P
V
CONV.LOSS
RIPPLE
C1
1
2
3
4
2 x f
2
1
BOOST
C2 V
2
OSC
1
_______________________________________________________________________________________
C1 (V
1
MAX1044
Switched-Capacitor Voltage Converters
ICL7660
RIPPLE
x C2
)
2
2
LV
2V
V
2 x ESR
OUT
OUT RIPPLE
Increasing Efficiency
8
7
6
5
2
V
C2
C
0.1µF
C2
10µF
I
BYPASS
OUT
x f
V+
V
OUT
OSC
-(V+)
/ 2
oscillator to 400Hz by connecting a 100pF capacitor to
OSC reduces the quiescent current to about 15µA.
Maintaining 20mA output current capability requires
increasing the bucket and reservoir capacitors to
100µF.
Note that lower capacitor values can be used for lower
output currents. For example, setting the oscillator to
40Hz by connecting a 1000pF capacitor to OSC pro-
vides the highest efficiency possible. Leaving the bucket
and reservoir capacitors at 100µF gives a maximum
I
a power conversion efficiency of 98%.
1) Connecting any input terminal to voltages greater
2) Never exceed maximum supply voltage ratings.
3) Do not connect C1 and C2 with the wrong polarity.
4) Do not short V+ to ground for extended periods with
5) Ensure that V
________________Application Circuits
Figure 8 shows a negative voltage converter, the most
popular application of the MAX1044/ICL7660. Only two
external capacitors are needed. A third power-supply
bypass capacitor is recommended (0.1µF to 10µF)
Figure 9. Voltage Doubler
OUT
than V+ or less than ground may cause latchup. Do
not apply any input sources operating from external
supplies before device power-up.
supply voltages above 5.5V present on other pins.
than GND (pin 3). Adding a diode in parallel with
C2, with the anode connected to V
to LV, will prevent this condition.
of 2mA, a no-load quiescent current of 10µA, and
1
2
3
4
MAX1044
OUT
ICL7660
Negative Voltage Converter
(pin 5) does not go more positive
General Precautions
8
7
6
5
V+
OUT
C1
V
OUT
and cathode
= 2(V+) - 2V
C2
D
9