CS5203 datasheet(4/6 Pages) FCI

4 / 6 page

The CS 5203 is designed to make use of multiple power

supplies, to reduce the dropout volta ge. One of the

advantages of the two supply approach is maximizing the

The second supply is at least 1V greater than output

voltage and is providing the power for the control circuitry

and supplies the drive current to the NPN output

transistor. Thi s allows the NPN output transistor to be

driven into saturation. For the control voltage the current

requirement is small equal to about 1% of the output

current. Thi s drive current becomes part of the output

current. The maximum voltage on the Control pin is 12V.

The maximumvoltageat the Power pin is 7V. By typingthe

control and power inputs together the CS5203 can also

be operated as a single supply device. In single supply

operation the dropout will be determined by the minimum

control voltage.

Both the fixed and adjustable versions have remote sense

pins, per mitting very accurate regulation of output

voltage.

As a result, over an output current range of

100mA to 3A , the typical load regulation is less than 1mV.

For the fixed voltages the adjust pin is brought out

allowing the user to improve transient response by

bypassing the internal resistor divider. Optimum transient

response is provided using a capacitor in the range of

0.1 F to 1 F f or bypassingthe A djust pin.

In add ition to the enhancements mentioned, the

reference accuracy has been improved a factor of two

with a guaranteed ini tial tolerance of

1% at 25

and

1.6% accuracy over the ful l temperature and load current

range

Typical applications for the CS 5203 include 3.3V to 2.5V

conversion w ith a 5V control supply, 5V to 4. 2V

conversion with a 12V control supply or 5V to 3. 6V

conversion with a 12V control supply. The dev ice is fully

protected against overcurrent and ov ertemperature

conditions.

The CS 5203 allows true Kelvin sensing for both the high

and low side of the load. A s a result the voltage regulation

at theload can be easily optimized. V oltage drops dueto

parasitic resistances between the regulator and the load

can be placed inside the regulation loop. The advantages

of remote sensing are illustrated in figures 1 through 3.

Figure 1 shows the device connected as a conventional 3

terminal regulator with the Sense lead connected directly

to theoutput of the device. Rp is theparasitic resistance

of theconnections betweenthe device and the load .

TraceA of figure3 illustrates the effect of Rp.

Figure 2 shows the device connected to take advantage

of the remote sense feature. The Sense pin and the top

of the resistor divider are connected to the top of the

load; the bottom of the resistor divider is connected to

the bottom of the load. The effect onoutput regulation

can be seen in trace B of figure 3.

It i s important to note that thevoltage drops due to Rp ,

are noteliminated; they will addto thedropout voltage of

the regulator regardless. The CS 5203 can control the

voltageat the load as long as the input-output voltageis

greater than the total of the dropoutvoltage of the device

plus the voltagedrop across Rp .

Th e c ircuit desi gn used in the CS 520 3 series requires the

use of an output capa citor as part of the de vice frequency

compensat ion.

Th e addition of 150

F aluminum

ele ctrolytic or a 22

F sol id tantalum on the output will

ensure stability for all operating conditions.

A pplic a tio n I n fo r m a tio n

Grounding and Output Sencing

S ta bil ity

C O N TRO L

C O N TR O L

5. 0V

3. 3V

R 2

(

)(

R )

O U T

R 1

R p

C S 5203

AD J

P O W E R

S E NS E

O UT P UT

F igure 1 . C onve nt ional Load Sen si ng

F igure 2 . Remote Load Sensing

F igure 3 . R em ote Sen si ng Im proves Loa d Regulation

LOAD

TI ME

V O UT

F IG U R E 1

V O UT

F IG U R E 2

IO UT

CS-5203 3 Amp Low Dropout Positive Voltage Regulator

efficiency.

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