ADM7160ACPZN1.8-R2 datasheet(16/24 Pages) AD

16 / 24 page

ADM7160

Data Sheet

Rev. 0 | Page 16 of 24

Figure 41 and Figure 42 show the connection of 4.7 μF capaci-

tors on the VIN and VOUT pins for the 5-lead TSOT and 6-lead

LFCSP packages, respectively.

CIN

4.7µF

COUT

4.7µF

VOUT = 2.5V

VIN = 2.9V

VOUT

VIN

GND

ADM7160

OFF

NC = NO CONNECT. DO NOT

CONNECT TO THIS PIN.

Figure 41. 5-Lead TSOT with 4.7 μF Input and Output Capacitors

ADM7160

TOP VIEW

(Not to Scale)

GND

VOUT

VIN

NC = NO CONNECT. DO NOT

CONNECT TO THIS PIN.

OFF

CIN

4.7µF

COUT

4.7µF

VIN = 2.9V

VOUT = 2.5V

Figure 42. 6-Lead LFCSP with 4.7 μF Input and Output Capacitors

THERMAL CONSIDERATIONS

In most applications, the ADM7160 does not dissipate much

heat due to its high efficiency. However, in applications with

high ambient temperature and a high supply voltage-to-output

voltage differential, the heat dissipated in the package 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 ADM7160

enters thermal shutdown. To prevent any permanent damage, the

regulator recovers only after the junction temperature decreases

below 135°C. Therefore, thermal analysis for the selected applica-

tion 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

ADM7160 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 power device, and thermal resistance between

the junction and ambient air (θJA). The θJA value is dependent on

the package assembly compounds used and the amount of copper

used to solder the package GND pin and the exposed pad (in the

case of the LFCSP) to the PCB.

Table 6 shows typical θJA values for the 5-lead TSOT and 6-lead

LFCSP packages for various PCB copper sizes.

Table 6. Typical θJA Values

Copper Size (mm2)

θJA (°C/W)

TSOT

LFCSP

170

231.2

152

161.8

100

146

150.1

300

134

111.5

500

131

91.8

Device soldered to minimum size pin traces.

Table 7 shows the typical ΨJB values for the 5-lead TSOT and

6-lead LFCSP.

Table 7. Typical ΨJB Values

Package

ΨJB (°C/W)

TSOT

LFCSP

28.3

The junction temperature of the ADM7160 can be calculated

using the following equation:

TJ = TA + (PD × θJA)

(2)

where:

TA is the ambient temperature.

θJA is the junction-to-ambient thermal resistance of the package.

PD is the power dissipation in the die, given by

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

(3)

where:

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

ILOAD is the load current.

IGND is the ground current.

Power dissipation due to ground current is quite small and can

be ignored. Therefore, the junction temperature equation can

be simplified as follows:

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

(4)

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

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

minimum copper size requirement exists for the PCB to ensure

that the junction temperature does not exceed 125°C.

Figure 43 through Figure 54 show junction temperature

calculations for various ambient temperatures, load currents,

input-to-output voltage differentials, and areas of PCB copper.

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