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Thermal Guidelines

Figure 3. Ch 1 OUT 1 -1.8-V Crosstalk Response, Ch2 OUT 2 – 2.8-V Transient Response for VIN at 3.3-V,

Ch 3 OUT 2 Load Current Transient

5 Thermal Guidelines

Thermal management is a key component of design of any power converter and is especially important

when the power dissipation in the LDO is high. Use the following formula to approximate the maximum

power dissipation for the particular ambient temperature:

T_j = T_a + Pd x q_ja

where T_j is the junction temperature, T_a is the ambient temperature, P_d is the power dissipation in the

device, and q_ja is the thermal resistance from junction to ambient. All temperatures are in degrees

Celsius. The maximum silicon junction temperature, T_j, must not be allowed to exceed 150°C. The layout

design of the copper trace and plane areas must be used effectively as thermal sinks in order to avoid T_j

from exceeding the absolute maximum rating under all temperature conditions and voltage conditions

across the part.

Note that because the TLV710xxxx consists of two separate LDOs in the same package, the total

dissipated power, P_d, is the sum of the power dissipated in each LDO channel separately calculated as

follows:

P_d = (Vin – Vout_1) x Iout_1 + (Vin – Vout_2) x Iout_2

where Vin is the input supply voltage at the VIN connector, Vout_1 is the output voltage at OUT 1, Iout_1

is the output load current from OUT 1, Vout_2 is the output voltage at OUT_2, and Iout_2 is the output

load current from OUT 2.

The thermal design of the PCB must be carefully considered in the layout. It is difficult to calculate the

thermal resistance for a custom layout with a unique copper area attached to each pin of the IC. repeats

information from the Dissipation Ratings Table of the TPS710xx data sheet for comparison with the

thermal resistance, q_ja, calculated for this EVM to show the wide variation in thermal resistances for

given copper areas. The high-K value is determined using a standard JEDEC high-k (2s2p) board with

dimensions of 3 inch x 30 inch with 1-ounce internal power and ground planes and 2-ounce copper traces

on top and bottom of the board.

SLVU404–September 2010 TLV7101828EVM-595

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