ADP190ACBZ-R7 datasheet(12/16 Pages) AD

12 / 16 page

ADP190/ADP191

Rev. D | Page 12 of 16

The turn-off time is defined as the delta between the time from

90% to 10% of VOUT reaching its final value. It is also dependent

on the RC time constant.

The ADP191 incorporates an internal output discharge resistor

to discharge the output capacitance when the ADP191 output is

disabled. See Figure 28 and Figure 29 for a comparison of turn-

off times.

CH1 1V

CH2 500mV

M10µs

A CH1

30.36µs

VOUT = 1.8V

VEN = 3.6V

ILOAD = 200mA,

CLOAD = 1µF

ILOAD = 100mA,

CLOAD = 1µF

ILOAD = 100mA,

CLOAD = 4.7µF

VEN

Figure 28. ADP190 Typical Turn-Off Time, Various Load Currents

CH1 2.00V

CH3 500mV

M200µs

A CH1

600mV

T 10.20%

VEN

VOUT

Figure 29. ADP191 Typical Turn-Off Time, Load Current = 0 mA

THERMAL CONSIDERATIONS

In most applications, the ADP190/ADP191 do not dissipate

much heat due to their low on-channel resistance. However, in

applications with high ambient temperature and load current,

the heat dissipated in the package can be large enough to cause

the junction temperature of the die to exceed the maximum

junction temperature of 125°C.

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 1.

To guarantee reliable operation, the junction temperature of

the ADP190/ADP191must not exceed 125°C. To ensure that the

junction temperature stays below this maximum value, the user

must be aware of the parameters that contribute to junction

temperature changes. These parameters include ambient temper-

ature, power dissipation in the power device, and thermal

resistances between the junction and ambient air (θJA). The θJA

value is dependent on the package assembly compounds that

are used and the amount of copper used to solder the package

GND pin to the PCB. Table 6 shows typical θJA values of the 4-ball

WLCSP for various PCB copper sizes. Table 7 shows the typical

ΨJB value of the 4-ball WLCSP.

Table 6. Typical θJA Values for WLCSP

Copper Size (mm2)

θJA (°C/W)

260

159

100

157

300

153

500

151

1 Device soldered to minimum size pin traces.

Table 7. Typical ΨJB Values

Package

ΨJB

Unit

4-Ball WLCSP

58.4

°C/W

The junction temperature of the ADP190/ADP191can be

calculated from the following equation:

TJ = TA + (PD × θJA)

(1)

where:

TA is the ambient temperature.

PD is the power dissipation in the die, given by

PD = [(VIN − VOUT) × ILOAD] + (VIN × IGND)

(2)

where:

ILOAD is the load current.

IGND is the ground current.

VIN and VOUT are the input and output voltages, respectively.

Power dissipation due to ground current is quite small and

can be ignored. Therefore, the junction temperature equation

simplifies to the following:

TJ = TA + {[(VIN − VOUT) × ILOAD] × θJA}

(3)

As shown in Equation 3, 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

that the junction temperature does not rise above 125°C. Figure 30

to Figure 35 show junction temperature calculations for different

ambient temperatures, load currents, VIN to VOUT differentials,

and areas of PCB copper.

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