ADP194ACBZ-R7 datasheet(11/12 Pages) AD

11 / 12 page

ADP194

Rev. 0 | Page 11 of 12

THERMAL CONSIDERATIONS

Power dissipation due to ground current is quite small and

can be ignored. Therefore, the junction temperature equation

simplifies to the following:

In most applications, the ADP194 does not dissipate much heat

due to its low on-channel resistance. However, in applications

with high ambient temperature and high load current, the heat

dissipated in the package can cause the junction temperature of

the die to exceed the maximum junction temperature of 125°C.

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

(3)

In cases where the board temperature is known, use the thermal

characterization parameter, ΨJB, to estimate the junction temper-

ature rise. Maximum junction temperature (TJ) is calculated

from the board temperature (TB) and power dissipation (PD)

using the formula

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.

TJ = TB + (PD × ΨJB)

(4)

To guarantee reliable operation, the junction temperature of

the ADP194 must 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 temperature, power

dissipation in the 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 5 shows typical θJA values of the 4-ball WLCSP for various

PCB copper sizes. Table 6 shows the typical ΨJB value of the

4-ball WLCSP.

PCB LAYOUT CONSIDERATIONS

The heat dissipation capability of the package can be improved

by increasing the amount of copper attached to the pins of the

ADP194. However, as listed in Table 5, a point of diminishing

returns is eventually reached, beyond which an increase in the

copper size does not yield significant heat dissipation benefits.

It is critical to keep the input and output traces as wide and as

short as possible to minimize the circuit board trace resistance.

Table 5. 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 6. Typical ΨJB Values

Package

ΨJB

Unit

4-Ball WLCSP

58.4

°C/W

The junction temperature of the ADP194 is calculated from the

following equation:

Figure 25. ADP194 PCB Layout

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.

ADP194ACBZ-R7 数据表(PDF) 11 Page - Analog Devices

ADP194ACBZ-R7 数据表(HTML) 11 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12

数据表下载