TPS1663 datasheet(18/30 Pages) TI1

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(UVLOR)

(UV)

(OVPR)

(OV)

ILIM

18k

TPS1663

SLVSET9A – SEPTEMBER 2018 – REVISED OCTOBER 2018

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9.2.2 Detailed Design Procedure

9.2.2.1 Programming the Current-Limit Threshold R(ILIM) Selection

The R(ILIM) resistor at the ILIM pin sets the over load current limit, this can be set using Equation 7.

where

•

ILIM = 1 A

(7)

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

9.2.2.2 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.

(8)

(9)

For minimizing the input current drawn from the power supply {I(R123) = V(IN) / (R1 + R2 + R3)}, it is recommended

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 20x 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 k

Ω.

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

9.2.2.3 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 and Figure 11 illustrates the inrush current limiting performance during 50 V hot-plug in

condition.

9.2.2.3.1

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 Absolute Maximum Ratings table). Typical resistance value in the range of 10 kΩ to 100 kΩ is recommended

for RPGOOD. Figure 13 and Figure 15 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. A minimum of 0.1 µF is

recommended for C(IN).

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