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SC4437

9

Advantage Over Shunt References

The SC4437 is a low power precision series voltage

reference. The series reference has major advantages over

shunt references when the load current has variations and

the reference is powered by a battery. A shunt reference

requires a resistance to connect the input and the output.

This resistance will be designed to consume the maximum

load current. When the actual load current is smaller than

the maximum load current, the difference will be

consumed by the reference. This behavior not only reduce

efficiency but also increase the thermal stress on the

device, thus is not desirable. On the contrary, the series

reference consumes the same current as the load. When

there is no load current required, the device itself

Precision Reference Over Wide Input Voltage Range, Load

Conditions and Operating Temperatures

The SC4437 can maintain 1% precision regulation over

wide load range, operating temperature condition and

input voltage range. To provide 3.3V output voltage, the

load can range from 0 to 20mA; the temperature can

from V

temperature conditions. The input voltage range should

be selected based on the drop out voltage speci cation.

Although the SC4437 can maintain tight regulation over

wide operating conditions, attention should be paid to

the thermal stress of the device. For example, with the

input voltage of 28V and the load current of 20mA, the

power consumption on the device is

P = (28V-3.3V)*0.02A = 0.494W

consumption on the chip gives an ambient to junction

is higher than 25 °C, then the junction temperature will be

higher than 125°C, thus should be avoided.

Input and Output Capacitances

The SC4437 is stable with or without output capacitors

under all load conditions. Adding output capacitances can

improve the dynamic response under load transient. In

order to obtain optimum performance under load

capacitor placed at the output.

Reverse Battery Connection Protection

The SC4437 has reverse battery connection protection.

When the input and ground is reversely connected, the

leakage current from the input is very small (maximum 6

µ

A), protecting both the battery and the device itself.

Load Transient Responses

The following gure shows the circuit setup to test the 1

mA load transient response.

3.3V

IN

OUT

GND

SC4437

C

IN

0.1 µF

5.8V

(optional)

C

O

3.3V

2.3V

1 k

Without output capacitance, the transient response is

shown below.

The high overshoot is due to the high resistance at high

frequency without output capacitance.

signi cantly. The gure below shows the 1mA transient

Applications Information