DAC7750IPWPR.B datasheet(41/56 Pages) TI2

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11.1.1 Thermal Considerations

The DACx750 is designed for a maximum junction temperature of 150°C. In cases where the maximum AVDD is

driving maximum current into ground, this junction temperature can be exceeded. Use Equation 7 to determine

the maximum junction temperature that can be reached.

Power dissipation = (TJ max – TA) / θJA

(7)

where

• TJ max = 150°C

• TA is the ambient temperature

• θJA is the package-dependent, junction-to-ambient thermal resistance, found in Section 7.4.

The power dissipation is calculated by multiplying all the supply voltages with the currents supplied, which are

found in the Power Requirements subsection of Section 7.5.

Consider an example: IOUT is enabled, supplying 24 mA into GND with a 25°C ambient temperature, AVDD

of 24 V, and DVDD is generated internally. From the Section 7.5, the max value of AIDD = 3 mA when IOUT

is enabled and DAC code = 0x0000. Also, the max value of DIDD = 1 mA. Accordingly, the worst-case power

dissipation is 24 V × (24 mA + 3 mA + 1 mA) = 672 mW. Using the θJA value for the TSSOP package, we

get TJ max = 25°C + (32.3 × 0.672)°C = 46.7°C. At 85°C ambient temperature, the corresponding value of TJ

max is 106.7°C. Using this type of analysis, the system designer can both specify and design for the equipment

operating conditions. Note that for enhanced thermal performance, connect the thermal pad in both packages to

a copper plane.

11.2 Layout Example

Figure 11-1 shows an example layout for the DACx750 device based on a similar layout for the DACx760 from

TIPD153.

Analog

Supply

Decoupling

GND

AVDD

DVDD

External RSET

(Optional)

External

Boost Transistor

(Optional)

Digital I/O

CAP1 / CAP2

Capacitance

(Optional)

Analog Supply

Series Resistance

Digital

Supply

Decoupling

ALARM

Pull-up

Resistance

Reference

Capacitance

HART

Input

IOUT

R3-SENSE

Figure 11-1. Example Layout

www.ti.com

DAC7750, DAC8750

SBAS538D – DECEMBER 2013 – REVISED DECEMBER 2021

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