TPS746 datasheet(29/44 Pages) TI

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8.2.2.2 Thermal Dissipation

The junction temperature can be determined using the junction-to-ambient thermal resistance (RθJA) and the

total power dissipation (PD). Use Equation 7 to calculate the power dissipation. Multiply PD by RθJA as Equation

8 shows and add the ambient temperature (TA) to calculate the junction temperature (TJ).

PD = (IGND+ IOUT) × (VIN – VOUT)

(7)

TJ = RθJA × PD + TA

(8)

Calculate the maximum ambient temperature as Equation 9 shows if the (TJ(MAX)) value does not exceed 125°C.

Equation 10 calculates the maximum ambient temperature with a value of 109.85°C.

TA(MAX) = TJ(MAX) – RθJA × PD

(9)

TA(MAX) = 150°C – 80.3°C/W × (3.8 V – 3.3 V) × (1 A) = 109.85°C

(10)

8.2.3 Application Curve

Frequency (Hz)

-10

100

10k

100k

10M

ILOAD = 10 mA

ILOAD = 100 mA

ILOAD = 250 mA

ILOAD = 500 mA

ILOAD = 1 A

VIN = 3.8 V, VOUT = 3.3 V, COUT = 2.2 µF

Figure 8-10. PSRR vs Frequency and ILOAD

9 Power Supply Recommendations

The TPS745-Q1 is designed to operate from an input voltage supply range from 1.5 V to 6.0 V. The input voltage

range provides adequate headroom in order for the device to have a regulated output. This input supply must be

well regulated. If the input supply is noisy, additional input capacitors with low ESR may help improve output

noise performance. Connect a low output impedance power supply directly to the IN pin of the TPS746-Q1.

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TPS746-Q1

SBVS358B – JUNE 2018 – REVISED JANUARY 2021

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TPS746 Datasheet(PDF) 29 Page - Texas Instruments