APL3200 Просмотр технического описания (PDF) - Anpec Electronics

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APL3200

Dual-Input, USB/AC Adapter, 1-Cell Li+ Charger with OVP and Thermal Regulation

Anpec Electronics 

APL3200

Applicaiton Information

Input Overvoltage Protection Switch

Connect a P-channel MOSFET between DCLV and DC to

protect the DCLV input pin from over-voltage up to 18V.

When DC voltage is above 6.4V OVP threshold, the DCOK

will be pulled high to turn off the P-channel MOSFET. The

P-channel MOSFET will be turned on again until the DC

voltage is below the OVP threshold. If the OVP function is

not needed, leave the DCOK open and tie the DC pin to

DCLV pin.

Battery-Load Switch

When an AC adapter or USB power is connected to

charger, some systems prefer that system load is

supplied from the AC adapter or USB power rather than

from the battery. In these systems, the battery is

permanently connected to system load. If the battery is

completely discharged, the system might not ready to

operate immediately. If the battery-load switch function is

needed, uses external components D1, D2, Q1, Q2, and

Q3 to achieve the function.

Typical Application Circuit 3 shows the full-featured circuit.

When input power is supplied, the Q1 disconnects the

battery from the system load. The input can power the

system through D1, D2, Q2, and Q3 when either USB or

AC power is present. Typical Application Circuit 4 shows

the partial battery-load switching. AC adapter power is

routed directly to the battery but USB power is not. When

the USB power is connected, total USB current is set by

USEL and system power is drawn from the battery through

D2.

STAT Pins

The STAT1 and STAT2 outputs indicate various charge

status. These two pins can be used to drive LEDs or

communicate to the host processor. When status pins

are monitored by a processor, there should be a 10kΩ

pull-up resistor to connect each status pin and the V of

CC

the processor; furthermore, when the status is viewed by

LED, the LED with a current rating is less than 10mA and

a resistor should be selected to connect LED in series,

so the current will be limited to the desired current value.

The resistor is calculated by the following equation:

RLED = (VIN − VLED _ ON)

PD

In other words, the LED and resistor between the input

and each status pin shoule in series.

Capacitor Selection

Typically, a 4.7µF ceramic capacitor is used to connect

from DC/USB to the GND. For high charging current, it is

recommended to use a larger input bypass capacitance

to reduce supply noise. Note that if the OVP function is

used, the DC should protect against the high DC input

voltage, so the voltage rating of the DC input capacitor

must be larger than 25V.

There is a ceramic capacitor connecting from BATT to the

GND for proper stability. To work well with most

applications, at least a 2.2µF X5R ceramic capacitor is

required.

Thermal Consideration

The APL3200 is available in a thermally enhanced QFN

package with an exposed pad. It is recommended to con-

nect the exposed pad to a large copper ground plane on

the backside of the circuit board through several ther-

mal vias for heatsinking. The exposed pad transfers

heat away from the device, allowing the APL3200 to

charge the battery with maximum current while minimiz-

ing the increase in die temperature.

The most common measure of package thermal perfor-

mance is thermal resistance measured from the device

junction to the air surrounding the package surface (θJA).

The θJA can be calculated by the following equation:

θJA = TJ − TA

PD

where:

TJ=device junction temperature

T = ambient temperature

A

PD=device power dissipation

The device power dissipation, PD, is the function of the

charge rate and the voltage drop across the internal FET.

It can be calculated by the following equation:

Copyright © ANPEC Electronics Corp.

17

Rev. A.5 - Apr., 2009

www.anpec.com.tw

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