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Detailed Description

The ICL7663S is a CMOS integrated circuit incorporating all

the functions of a voltage regulator plus protection circuitry

on a single monolithic chip. Referring to the Functional

Diagram, the main blocks are a bandgap-type voltage

reference, an error amplifier, and an output driver with both

PMOS and NPN pass transistors.

The bandgap output voltage, trimmed to 1.29V

±15mV for

are compared in amplifier A. Error amplifier A drives a

P-channel pass transistor which is sufficient for low (under

about 5mA) currents. The high current output is passed by

an NPN bipolar transistor connected as a follower. This

configuration gives more gain and lower output impedance.

Logic-controlled shutdown is implemented via a N-Channel

MOS transistor. Current-sensing is achieved with

which can be used in combination with amplifier A to

generate programmable-temperature-coefficient output

voltages.

The amplifier, reference and comparator circuitry all operate

at bias levels well below 1

µA to achieve extremely low

quiescent current. This does limit the dynamic response of

the circuits, however, and transients are best dealt with

outside the regulator loop.

Basic Operation

The ICL7663S is designed to regulate battery voltages in the

5V to 15V region at maximum load currents of about 5mA to

30mA. Although intended as low power devices, power

dissipation limits must be observed. For example, the power

dissipation in the case of a 10V supply regulated down to 2V

with a load current of 30mA clearly exceeds the power

dissipation rating of the Mini-DIP:

The circuit of Figure 8 illustrates proper use of the device.

CMOS devices generally require two precautions: every

input pin must go somewhere, and maximum values of

applied voltages and current limits must be rigorously

observed. Neglecting these precautions may lead to, at the

least, incorrect or nonoperation, and at worst, destructive

device failure. To avoid the problem of latchup, do not apply

inputs to any pins before supply voltage is applied.

Input Voltages - The ICL7663S accepts working inputs of

1.5V to 16V. When power is applied, the rate-of-rise of the

input may be hundreds of volts per microsecond. This is

potentially harmful to the regulators, where internal

operating currents are in the nanoampere range. The

0.047

µF capacitor on the device side of the switch will limit

inputs to a safe level around 2V/

µs. Use of this capacitor is

suggested in all applications. In severe rate-of-rise cases, it

may be advisable to use an RC network on the SHutDowN

pin to delay output turn-on. Battery charging surges,

transients, and assorted noise signals should be kept from

the regulators by RC filtering, zener protection, or even

fusing.

arrangements of these resistors, using a potentiometer,

applications the potentiometer may be eliminated by using

guaranteed to be 1.29V

±15mV and when used with ±1%

will be within

±2.7% of ideal.

drain current. However, some load current is required for

proper operation, so for extremely low-drain applications it is

necessary to draw at least 1

µA. This can include the current

at low load currents, while the low limit is the reference

voltage. The minimum input-output differential in each

Output Currents - Low output currents of less than 5mA are

obtained with the least input-output differential from the

open in this case).

SHDN

SENSE

GND

1

µA MIN

+

-

(7663 ONLY)

ON

OFF

1M

Ω

0.047

µF

+

-

M

NOTES:

9. IQ quiescent currents measured at GND pin by meter M.

FIGURE 7. ICL7663S TEST CIRCUIT

ICL7663S