TLV755P datasheet(20/49 Pages) TI

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7.2.2 Detailed Design Procedure

7.2.2.1 Input Current

During normal operation, the input current to the LDO is approximately equal to the output current of the LDO.

During start-up, the input current is higher as a result of the inrush current charging the output capacitor. Use

Equation 5 to calculate the current through the input.

OUT(t)

OUT

´ dV

(t)

OUT(t)

LOAD

(5)

where:

• VOUT(t) is the instantaneous output voltage of the turn-on ramp

• dVOUT(t) / dt is the slope of the VOUT ramp

• RLOAD is the resistive load impedance

7.2.2.2 Thermal Dissipation

Junction temperature is determined using the junction-to-ambient thermal resistance (RθJA) and the total power

dissipation (PD). Use Equation 6 to calculate the power dissipation. Multiply PD by RθJA as Equation 7 shows and

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

PD = (IGND+ IOUT) × (VIN – VOUT)

(6)

TJ = RθJA × PD + TA

(7)

Calculate the maximum ambient temperature as Equation 8 shows if the (TJ(MAX)) value does not exceed 125°C.

Equation 9 calculates the maximum ambient temperature with a value of 99.95°C.

TA(MAX) = TJ(MAX) – RθJA × PD

(8)

TA(MAX) = 125°C – 100.2°C/W × (4.3V – 3.3V) × (0.25A) = 99.95°C

(9)

7.2.3 Application Curve

Frequency (Hz)

100

10k

100k

10M

IOUT = 10 mA

IOUT = 50 mA

IOUT = 100 mA

IOUT = 500 mA

VIN = 4.3V, VOUT = 3.3V

Figure 7-5. PSRR vs Frequency (4.3V to 3.3V)

7.3 Power Supply Recommendations

Connect a low output impedance power supply directly to the IN pin of the TLV755P. If the input source is

reactive, consider using multiple input capacitors in parallel with the 1µF input capacitor to lower the input supply

impedance over frequency.

TLV755P

SBVS320D – NOVEMBER 2017 – REVISED SEPTEMBER 2024

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