MCP73113 datasheet(22/34 Pages) MICROCHIP

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MCP73113/4

DS22183C-page 22

6.1.1.2

Thermal Considerations

The worst-case power dissipation in the battery

charger occurs when the input voltage is at the

maximum and the device has transitioned from the

Preconditioning mode to the Constant-current mode. In

this case, the power dissipation is:

Power dissipation with a 5V, ±10% input voltage

source, 500 mA ±10% and preconditioning threshold

voltage at 2.7V is:

EQUATION 6-1:

This power dissipation with the battery charger in the

DFN-10 package will result approximately 63

°C above

room temperature.

6.1.1.3

External Capacitors

The MCP73113/4 are stable with or without a battery

load. In order to maintain good AC stability in the

Constant-voltage mode, a minimum capacitance of

1 µF is recommended to bypass the VBAT pin to VSS.

This capacitance provides compensation when there is

battery

load.

addition,

the

battery

and

interconnections appear inductive at high frequencies.

These elements are in the control feedback loop during

Constant-voltage

mode.

Therefore,

the

bypass

capacitance may be necessary to compensate for the

inductive nature of the battery pack.

A minimum of 16V rated 1 µF, is recommended to apply

for output capacitor and a minimum of 25V rated 1 µF,

is recommended to apply for input capacitor for typical

applications.

TABLE 6-1:

MLCC CAPACITOR EXAMPLE

Virtually any good quality output filter capacitor can be

used,

independent

the

capacitor’s

minimum

Effective Series Resistance (ESR) value. The actual

value of the capacitor (and its associated ESR)

depends on the output load current. A 1 µF ceramic,

tantalum or aluminum electrolytic capacitor at the

output is usually sufficient to ensure stability.

6.1.1.4

Reverse-Blocking Protection

The MCP73113/4 provide protection from a faulted or

shorted input. Without the protection, a faulted or

shorted input would discharge the battery pack through

the body diode of the internal pass transistor.

PowerDissipation

DDMAX

PTHMIN

–

() I

REGMAX

Where:

VDDMAX = the maximum input voltage

IREGMAX = the maximum fast charge current

VPTHMIN = the minimum transition threshold

voltage

PowerDissipation

5.5V

2.7V

–

() 550mA

1.54W

MLCC

Capacitors

Temperature

Range

Tolerance

X7R

-55

°C to +125°C

±15%

X5R

-55

°C to +85°C

±15%

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