OPA863 datasheet(29/52 Pages) TI

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9.4.1.1 Thermal Considerations

The OPAx863 does not require heat sinking or airflow in most applications. The maximum allowed junction

temperature sets the maximum allowed internal power dissipation. Do not allow the maximum junction

temperature to exceed 150°C.

Operating junction temperature (TJ) is given by,

TJ = TA + PD x RƟJA

(4)

where

• TA is the ambient temperature

• PD is the total power dissipation internal to the amplifier

• RƟJA is the junction-to-ambient thermal resistance

The total power dissipation PD = PDQ + PDL

where

• PDQ = (VS+ ‐ VS-) x IQ, is the power dissipation due to the amplifier quiescent current

• PDL(max) = VS 2 / (4 × RL), is the internal power dissipation due to the output load current

As a worst-case example, compute the maximum TJ using an OPA2863-DGK (VSSOP package) configured as

a unity gain buffer, operating on ±6-V supplies at an ambient temperature of 25°C and driving a grounded 500-Ω

load.

PD = 12 V × 2 mA + 62 / (4 × 500 Ω) = 42 mW

(5)

Maximum TJ = 25°C + (0.042 W × 180.3°C/W) = 33°C, which is much less than the maximum allowed junction

temperature of 150°C.

9.4.2 Layout Example

Place bypass capacitors

close t o power pins

Place gain and feedback r esistors close

to pins to mi nimize str ay capacit ance

Place ser ies output resistors close

to output pin to m inimi ze

par asitic capacitance

Ground and power plane removed

from inner layers. Ground fill on outer

layer s also removed

Ground and power plane exist on inner

layer s.

Place bypass capacitors

close t o power pins

Remove GND and Power plane under

output and i nv er ting pins to m inimize

stray PCB capacitance

BYP

S-

BYP

S+

Representati ve schematic of a

single channel

BYP

Figure 9-7. Layout Recommendation for Dual-Channel DGK Package

www.ti.com

OPA863, OPA2863, OPA4863

SBOS982J – JUNE 2020 – REVISED JUNE 2023

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