I

=

OUT(t)

C

OUT

OUT

´ dV

(t)

dt

V

OUT(t)

R

LOAD

+

IN

OUT

GND

EN

PG

TPS746

VOUT

VIN

FB

CIN

COUT

RPG

VEN

VPG

R2

R1

23

TPS746

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SBVS337A – APRIL 2018 – REVISED DECEMBER 2018

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8.3 Typical Application

Figure 50 shows the typical application circuit for the TPS746. Input and output capacitances must be at least

1 µF.

Figure 50. TPS746 Typical Application

8.3.1 Design Requirements

Use the parameters listed in Table 2 for typical linear regulator applications.

Table 2. Design Parameters

PARAMETER

DESIGN REQUIREMENT

Input voltage

3.8 V

Output voltage

3.3 V, ±1%

Input current

1 A (maximum)

Output load

1-A DC

Maximum ambient temperature

70°C

8.3.2 Detailed Design Procedure

Input and output capacitors are required to achieve the output voltage transient requirements. Capacitance

values of 2.2 µF are selected to give the maximum output capacitance in a small, low-cost package; see the

Input and Output Capacitor Selection section for details.

Figure 46 illustrates the output voltage of the TPS746. Set the output voltage using the resistor divider; see the

section for details.

8.3.2.1 Input Current

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

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

Equation 6 to calculate the current through the input.

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

(6)

8.3.2.2 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)