:

ILIM

OL

18

R

18k

I

(7)

where

• ILIM = 1 A

Choose the closest standard 1% resistor value: R(ILIM) = 18 kΩ

10.2.2.2 Undervoltage Lockout and Overvoltage Set Point

The undervoltage lockout (UVLO) and overvoltage trip point are adjusted using an external voltage divider

network of R1, R2 and R3 connected between IN, UVLO, OVP and GND pins of the device. The values required

for setting the undervoltage and overvoltage are calculated by solving Equation 8 and Equation 9.

3

(OVPR)

(OV)

1

2

3

R

V

V

R

R

R

u

(8)

2

3

(UVLOR)

(UV)

1

2

3

R

R

V

V

R

R

R

u

(9)

For minimizing the input current drawn from the power supply [I(R123) = V(IN) / (R1 + R2 + R3)], TI recommends to

use higher value resistance for R1, R2 and R3.

However, the leakage current due to external active components connected at resistor string can add error

to these calculations. So, the resistor string current, I(R123), must be chosen to be 20 times greater than the

leakage current of UVLO and OVP pins.

From the device electrical specifications, V(OVPR) = 1.2 V and V(UVLOR) = 1.2 V. From the design requirements,

V(OV) is 55 V and V(UV) is 18 V. To solve the equation, first choose the value of R3 = 20.5 kΩ and use Equation 8

to solve for (R1 + R2) = 930 kΩ. Use Equation 9 and value of (R1 + R2) to solve for R2 = 43 kΩ and finally R1 =

887 kΩ.

Choose the closest standard 1% resistor values: R1 = 887 kΩ, R2 = 43 kΩ, and R3 = 20.5 kΩ.

10.2.2.3 Setting Output Voltage Ramp Time (tdVdT)

Use Equation 1 and Equation 2 to calculate required C(dVdT) for achieving an inrush current of 300 mA. C(dVdT)

= 22 nF. Figure 10-2 and Figure 10-3 illustrate the inrush current limiting performance during 50-V hot-plug in

condition.

10.2.2.3.1 Support Component Selections RPGOOD and C(IN)

The RPGOOD serves as pull-up for the open-drain output. The current sink by this pin must not exceed 10 mA

(see the Section 7.1 table). TI recommends typical resistance value in the range of 10 kΩ to 100 kΩ for RPGOOD.

Figure 10-5 and Figure 10-7 illustrate the power up and power down performance of the system respectively.

The CIN is a local bypass capacitor to suppress noise at the input. TI recommends a minimum of 0.1 µF for C(IN).

TPS1663

SLVSET9F – SEPTEMBER 2018 – REVISED FEBRUARY 2023

www.ti.com

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