APX9270 Просмотр технического описания (PDF) - Anpec Electronics

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APX9270

Direct PWM Variable Speed Fan Motor Driver

Anpec Electronics 

APX9270

Application Information (Cont.)

HB Bias Output and Hall Input Signals

The IC outputs a 1.3V voltage on HB pin to provide bias

for the external hall element. The IC also has two pins

IN+ and IN- to receive the hall signals from the hall

element. The hall signals are very weak so the layout

tracks must be short and far away from those noise

sources to avoid noise coupling. The hall input amplifier

has 20mV hysteresis. Therefore, the recommended dif-

ferential hall input voltage should be more than 60mV.

CT Capacitor

The capacitor that is connected from CT pin to GND

determines the shutdown time and restart time.

Locked Detection Time = CCT (× VCT1 − 0.2V)

ICT1

( ) Restart Time = CCT × VCT1 − VCT2

ICT1

( ) Shutdown Time = CCT × VCT1 − VCT2

ICT2

where

CCT = CT pin capacitor

For example:

V =12V,

CC

CCT=1µF

Locked Detection Time = 1.545 s

Restart Time = 0.909 s

Shutdown Time = 9.091 s

The value of charge capacitor in the range of 0.47µF to

1µF is recommended.

FG Resistor

The value of the FG resistor could be decided by the

following equation

RFG = V6VREG − VFG

IFG

For example:

V

6VREG

=

6V,

I

FG

=

5mA,

V

FG

=

0.2V,

R

FG

=

1.16kΩ

The value of resistor in the range of 1kΩ to 10kΩ is

recommended.

Thermal Pad Consideration

The thermal pad on the bottom of the TSSOP-20P pack-

age should be soldered down to a copper pad on the

circuit board. Heat can be conducted away from the ther-

mal pad through the copper plane to ambient. If the cop-

per plane is not on the top surface of the circuit board, 8 to

10 vias of 13 mil or smaller in diameter should be used to

thermally couple the thermal pad to the bottom plane. For

good thermal conduction, the vias must be plated through

and solder filled. The copper plane is used to conduct

heat away from the thermal pad should be as large as

practical.

If the ambient temperature is higher than 25οC, a larger

copper plane or forced-air cooling will be required to keep

the APX9270 junction temperature below the thermal pro-

tection temperature (160οC).

Thermal Consideration

Refer to “Maximum Power Dissipation vs. Ambient

Temperature”, the IC is safe to operate below the curve

and it will cause the thermal protection if the operating

area is above the line. For example, T = 50οC, the SSOP-

A

20 package maximum power dissipation is about 0.95W.

Power dissipation can be calculated by the following

equation:

( ) PD = VCC − VOUT1 − VOUT2 ×IOUT + VCC ×ICC

For example:

When VCC = 12V, ICC = 6mA, IOUT = 300mA, VOUT1 = 11.66V,

VOUT2 = 0.13V, then PD = 0.213W

According the power dissipation issue, we could adapt

this SSOP-20 package.

Copyright © ANPEC Electronics Corp.

12

Rev. A.3 - Jun., 2008

www.anpec.com.tw

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