CS8122YT5 datasheet(6/8 Pages) CHERRY

Part #	CS8122YT5

Description	2% 5V, 750mA Low Dropout Linear Regulator with Delayed RESET

Download	8 Pages

Scroll/Zoom	100%

Manufacturer	CHERRY [Cherry Semiconductor Corporation]

Direct Link	http://www.cherrycorp.com/

Logo

6 / 8 page

6

Application Notes

The output or compensation capacitor helps determine

three main characteristics of a linear regulator: start-up

delay, load transient response and loop stability.

The capacitor value and type should be based on cost,

availability, size and temperature constraints. A tantalum

or aluminum electrolytic capacitor is best, since a film or

ceramic capacitor with almost zero ESR can cause instabil-

ity. The aluminum electrolytic capacitor is the least expen-

sive solution, but, if the circuit operates at low tempera-

tures (-25¡C to -40¡C), both the value and ESR of the

capacitor will vary considerably. The capacitor manufac-

turers data sheet usually provides this information.

The value for the output capacitor COUT shown in the test

and applications circuit should work for most applica-

tions, however it is not necessarily the optimized solution.

To determine an acceptable value for COUT for a particular

application, start with a tantalum capacitor of the recom-

mended value and work towards a less expensive alterna-

tive part.

Step 1:

Place the completed circuit with a tantalum capac-

itor of the recommended value in an environmental cham-

ber at the lowest specified operating temperature and

monitor the outputs with an oscilloscope. A decade box

connected in series with the capacitor will simulate the

higher ESR of an aluminum capacitor. Leave the decade

box outside the chamber, the small resistance added by

the longer leads is negligible.

Step 2:

With the input voltage at its maximum value,

increase the load current slowly from zero to full load

while observing the output for any oscillations. If no oscil-

lations are observed, the capacitor is large enough to

ensure a stable design under steady state conditions.

Step 3:

Increase the ESR of the capacitor from zero using

the decade box and vary the load current until oscillations

appear. Record the values of load current and ESR that

cause the greatest oscillation. This represents the worst

case load conditions for the regulator at low temperature.

Step 4

: Maintain the worst case load conditions set in step

3 and vary the input voltage until the oscillations increase.

This point represents the worst case input voltage condi-

tions.

Step 5:

If the capacitor is adequate, repeat steps 3 and 4

with the next smaller valued capacitor. A smaller capaci-

tor will usually cost less and occupy less board space. If

the output oscillates within the range of expected operat-

ing conditions, repeat steps 3 and 4 with the next larger

standard capacitor value.

Step 6:

Test the load transient response by switching in

various loads at several frequencies to simulate its real

working environment. Vary the ESR to reduce ringing.

Step 7:

Remove the unit from the environmental chamber

and heat the IC with a heat gun. Vary the load current as

instructed in step 5 to test for any oscillations.

Once the minimum capacitor value with the maximum

ESR is found, a safety factor should be added to allow for

the tolerance of the capacitor and any variations in regula-

tor performance. Most good quality aluminum electrolytic

capacitors have a tolerance of ± 20% so the minimum

value found should be increased by at least 50% to allow

for this tolerance plus the variation which will occur at

low temperatures. The ESR of the capacitor should be less

than 50% of the maximum allowable ESR found in step 3

above.

The maximum power dissipation for a single output regu-

lator (Figure 1) is:

PD(max)={VIN(max)ÐVOUT(min)}IOUT(max)+VIN(max)IQ

(1)

where

VIN(max) is the maximum input voltage,

VOUT(min) is the minimum output voltage,

IOUT(max) is the maximum output current for the applica-

tion, and

IQ is the quiescent current the regulator consumes at

IOUT(max).

Once the value of PD(max) is known, the maximum permis-

sible value of RQJA can be calculated:

RQJA =

(2)

The value of RQJA can then be compared with those in

the package section of the data sheet. Those packages

with RQJA's less than the calculated value in equation 2

will keep the die temperature below 150¡C.

In some cases, none of the packages will be sufficient to

dissipate the heat generated by the IC, and an external

heatsink will be required.

150¡C - T

A

PD

Calculating Power Dissipation

in a Single Output Linear Regulator

Stability Considerations

VIN

Smart

Regulator

VOUT

IOUT

IIN

IQ

Control

Features

}

Figure 1: Single output regulator with key performance parameters

labeled.

Similar Part No. - CS8122YT5

Manufacturer	Part #	Datasheet	Description
ON Semiconductor	CS8122YT5	100Kb / 10P	2.0% 5.0 V, 750 mA Low Dropout Linear Regulator with Delayed RESET June, 2006 ??Rev. 7
ON Semiconductor	CS8122YT5G	100Kb / 10P	2.0% 5.0 V, 750 mA Low Dropout Linear Regulator with Delayed RESET June, 2006 ??Rev. 7

More results

Similar Description - CS8122YT5

Manufacturer	Part #	Datasheet	Description
Cherry Semiconductor Co...	CS8126	207Kb / 9P	5V, 750mA Low Dropout Linear Regulator with Delayed RESET
	CS8129	188Kb / 8P	5V, 750mA Low Dropout Linear Regulator with Lower RESET Threshold
	CS403	158Kb / 6P	5V, 750mA Linear Regulator with RESET
National Semiconductor ...	LM2925	223Kb / 8P	Low Dropout Regulator with Delayed Reset
HTC Korea TAEJIN Techno...	LM2925	228Kb / 8P	Low Dropout Regulator with Delayed Reset
National Semiconductor ...	LM2826	319Kb / 9P	Low Dropout Regulator with Delayed Reset
National Semiconductor ...	LM2926	404Kb / 10P	Low Dropout Regulator with Delayed Reset
ON Semiconductor	CS8126	121Kb / 12P	5.0 V, 750 mA Low Dropout Linear Regulator with Delayed RESET February, 2006 ??Rev. 16
ON Semiconductor	CS8126	167Kb / 9P	5.0 V, 750 mA Low Dropout Linear Regulator with Delayed RESET October, 2009 ??Rev. 18
National Semiconductor ...	LM9071	193Kb / 7P	Low-Dropout System Voltage Regulator with Delayed Reset

More results

CS8122YT5 Datasheet(PDF) 6 Page - Cherry Semiconductor Corporation

CS8122YT5 Datasheet(HTML) 6 Page - Cherry Semiconductor Corporation

Similar Part No. - CS8122YT5

Similar Description - CS8122YT5

Html Pages

1 2 3 4 5 6 7 8

Datasheet Download

Link URL