8
FN2853.7
September 4, 2015
Other Applications
Relay and Lamp Drivers
The ICL7667 is suitable for converting low power TTL or
CMOS signals into high current, high voltage outputs for
relays, lamps and other loads. Unlike many other level
translator/driver ICs, the ICL7667 will both source and sink
current. The continuous output current is limited to 200mA
by the I
2
R power dissipation in the output FETs.
Charge Pump or Voltage Inverters and Doublers
The low output impedance and wide V+ range of the
ICL7667 make it well suited for charge pump circuits. Figure
13A shows a typical charge pump voltage inverter circuit and
a typical performance curve. A common use of this circuit is
to provide a low current negative supply for analog circuitry
or RS232 drivers. With an input voltage of +15V, this circuit
will deliver 20mA at -12.6V. By increasing the size of the
capacitors, the current capability can be increased and the
voltage loss decreased. The practical range of the input
frequency is 500Hz to 250kHz. As the frequency goes up,
the charge pump capacitors can be made smaller, but the
internal losses in the ICL7667 will rise, reducing the circuit
efficiency.
Figure 14, a voltage doubler, is very similar in both circuitry
and performance. A potential use of Figure 13 would be to
supply the higher voltage needed for EEPROM or EPROM
programming.
Clock Driver
Some microprocessors (such as the CDP68HC05 families)
use a clock signal to control the various LSI peripherals of
the family. The ICL7667s combination of low propagation
delay, high current drive capability and wide voltage swing
make it attractive for this application. Although the ICL7667
is primarily intended for driving power MOSFET gates at
15V, the ICL7667 also works well as a 5V high-speed buffer.
Unlike standard 4000 series CMOS, the ICL7667 uses short
channel length FETs and the ICL7667 is only slightly slower
at 5V than at 15V.
FIGURE 13A. FIGURE 13B. OUTPUT CURRENT vs OUTPUT VOLTAGE
FIGURE 13. VOLTAGE INVERTER
1/2
ICL7667
+15V
10
µF
+
-
IN4001
47µF
+
-
-13.5V
IN4001
1kHz - 250kHz
SQUARE
WAVE
IN TTL
LEVELS
520 40 60 80 100
-4
-6
-8
-10
-12
-14
V
OUT
(V)
I
OUT
(mA)
SLOPE = 60
f = 10kHz
1/2
ICL7667
+15V
10
µF
+
-
IN4001
47µF
+
-
28.5V
IN4001
1kHz - 250kHz
+15
SQUARE
WAVE
IN TTL
LEVELS
FIGURE 14. VOLTAGE DOUBLER
ICL7667
