APL5537RDCTI-TRG 데이터 시트보기 (PDF) - Anpec Electronics

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APL5537RDCTI-TRG

Dual Channel 300mA Low Dropout Linear Regulator

Anpec Electronics 

APL5537

Application Information

Input Capacitor

The APL5537 requires proper input capacitors to supply

surge current during stepping load transients to prevent

the input rail from dropping. Because the parasitic induc-

tor from the voltage sources or other bulk capacitors to

the VIN limit the slew rate of the surge current, place the

Input capacitors near VIN as close as possible. Input ca-

pacitors should be larger than 1µF and a minimum ce-

ramic capacitor of 1µF is necessary.

Output Capacitor

The APL5537 needs a proper output capacitor to main-

tain circuit stability and improve transient response over

temperature and current. In order to insure the circuit

stability, the proper output capacitor value should be larger

than 1µF. With X5R and X7R dielectrics, 1µF is sufficient

at all operating temperatures. Large output capacitor

value can reduce noise and improve load-transient re-

sponse and PSRR, Figure 1 shows the curves of allow-

able ESR range as the function of load current for various

output capacitor values.

Region of Stable COUT ESR vs. Output Current

10

APL5537-OC

VCIINN==VCEONU=T4=.12µVF/X7R

1

Unstable Range

where (T -T ) is the temperature difference between the

JA

junction and ambient air. θJA is the thermal resistance

between Junction and ambient air. Assuming the TA=25oC

and maximum TJ=160oC (typical thermal limit threshold),

the maximum power dissipation is calculated as:

P (max)=(160-25)/165 = 0.82(W)

D

For normal operation, do not exceed the maximum junc-

tion temperature rating of TJ = 125oC. The calculated

power dissipation should be less than:

PD =(125-25)/165 = 0.61(W)

The GND provides an electrical connection to the ground

and channels heat away. Connect the GND to the ground

by using a large pad or a ground plane.

Layout Consideration

Figure 2 illustrates the layout. Below is a checklist for

your layout:

1. Please place the input capacitors close to the VIN.

2. Ceramic capacitors for load must be placed near the

load as close as possible.

3. To place APL5537 and output capacitors near the load

is good for performance.

4. Large current paths, the bold lines in figure 2, must

have wide tracks.

VIN

CIN

VIN

VOUT1

VOUT1

COUT1

0.1

Stable Range

0.01

Stable by Simulation Verify

ON

OFF

0.001

0

50 100 150 200 250 300

Output Current (mA)

Figure1. Stable COUT ESR Range

Operation Region and Power Dissipation

The APL5537 maximum power dissipation depends on

the thermal resistance and temperature difference be-

tween the die junction and ambient air. The TDFN1.6x

1.6-6 package power dissipation PD across the device is:

P

D

=

(T

J

-

T)

A

/

θJA

Copyright © ANPEC Electronics Corp.

10

Rev. A.7 - Oct., 2011

APL5537

EN1

VOUT2

EN2

GND

VOUT2

COUT2

Figure2. Large Current Paths

www.anpec.com.tw

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