ADP160/ADP161/ADP162/ADP163

Data Sheet

Rev. G | Page 16 of 24

Consider the case where a hard short from OUT to ground

occurs. At first, the ADP16x current limit so that only 320 mA

is conducted into the short. If self-heating of the junction is

great enough to cause its temperature to rise above 150°C,

thermal shutdown activates, turning off the output and

reducing the output current to zero. As the junction tempera-

ture cools and drops below 135°C, the output turns on and

conducts 320 mA into the short, again causing the junction

temperature to rise above 150°C. This thermal oscillation

between 135°C and 150°C causes a current oscillation between

320 mA and 0 mA that continues as long as the short remains

at the output.

Current and thermal limit protections are intended to protect

the device against accidental overload conditions. For reliable

operation, device power dissipation must be externally limited

so junction temperatures do not exceed 125°C.

THERMAL CONSIDERATIONS

In most applications, the ADP16x do not dissipate much heat due

to their high efficiency. However, in applications with high ambient

temperature and high supply voltage to output voltage differential,

the heat dissipated in the package is large enough that it can cause

the junction temperature of the die to exceed the maximum

junction temperature of 125°C.

When the junction temperature exceeds 150°C, the converter enters

thermal shutdown. It recovers only after the junction temperature

has decreased below 135°C to prevent any permanent damage.

Therefore, thermal analysis for the chosen application is very

important to guarantee reliable performance over all conditions.

The junction temperature of the die is the sum of the ambient

temperature of the environment and the temperature rise of the

package due to the power dissipation, as shown in Equation 2.

To guarantee reliable operation, the junction temperature of

the ADP16x must not exceed 125°C. To ensure the junction

temperature stays below this maximum value, the user needs to

be aware of the parameters that contribute to junction temperature

changes. These parameters include ambient temperature, power

dissipation in the power device, and thermal resistances between

on the package assembly compounds that are used and the amount

of copper used to solder the package GND pins to the PCB.

4-ball WLCSP for various PCB copper sizes. Table 9 shows the

θ

TSOT

WLCSP

170

260

50

152

159

100

146

157

300

134

153

500

131

151

Ψ

TSOT

WLCSP

42.8

58.4

The junction temperature of the ADP16x can be calculated

from the following equation:

(2)

where:

(3)

where:

Power dissipation due to ground current is quite small and can be

ignored. Therefore, the junction temperature equation simplifies to

the following:

(4)

As shown in Equation 4, for a given ambient temperature, input-

to-output voltage differential, and continuous load current, there

exists a minimum copper size requirement for the PCB to ensure

the junction temperature does not rise above 125°C. Figure 41 to

Figure 48 show the junction temperature calculations for the

differentials, and areas of PCB copper.

In the case where the board temperature is known, use the

temperature rise (see Figure 49 and Figure 50). Maximum

following formula:

(5)

and 43°C/W for the 5-lead TSOT package.

140

120

100

80

60

40

20

0

0.3

4.8

4.3

3.8

3.3

2.8

2.3

1.8

1.3

0.8

MAXIMUM JUNCTION TEMPERATURE