MCP73830L datasheet(14/24 Pages) MICROCHIP

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MCP73830/L

DS20005049E-page 14

 2011-2019 Microchip Technology Inc.

FIGURE 6-3:

Input Overvoltage Protection Example.

6.1.1.3

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 Preconditioning mode to

Constant-Current mode. In this case, the power

dissipation is:

EQUATION 6-1:

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

source, 200 mA, ±10%, and preconditioning threshold

voltage at 3.0V is:

EQUATION 6-2:

This power dissipation with the battery charger in the

2x2 TDFN-6 package will result in a temperature of

approximately +10.45

C (PCB mounted, infinite heat

sink) above room temperature.

In the worst case (minimum PCB copper, natural

convection), the temperature will increase by +50.1°C

above the room temperature.

The actual junction temperature is described in

equation 6-3:

EQUATION 6-3:

The MCP73830/L devices are stable with or without a

battery load. In order to maintain good AC stability in

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

no battery load. In addition, the battery and intercon-

nections appear inductive at high frequencies. These

elements are in the control feedback loop during

Constant Voltage mode. Therefore, the bypass capaci-

tance 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 the output capacitor and a minimum of 25V rated

1 µF is recommended to apply for the input capacitor

for typical applications.

STAT

VDD

VBAT

PROG

Regulated

Wall Cube

0.5



VSS

SMAJ5.0A/AC

TVS

CIN

2 mm x 2 mm DFN

MCP73830/L

Cable Resistance

PowerDissipation

VDDMAX VPTHMIN

–

 I

REGMAX



Where:

VDDMAX = The maximum input voltage

IREGMAX = The maximum fast charge current

VPTHMIN = The minimum transition threshold

voltage

PowerDissipation = (5.5V – 3.0V)

 220 mA = 0.55W

TABLE 6-1:

MLCC CAPACITOR EXAMPLE

MLCC

Capacitors

Temperature

Range

Tolerance

X7R

-55

C to +125C±15%

X5R

-55

C to +85C

±15%

TA 10.45C0.55W HA



Where:

TJ = Junction Temperature

TA = Ambient Temperature

+10.45

C = Temperature Increase due to JC

HA = Heat Sink to Ambient Thermal

Resistance

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