0.97

ILIM

1.004

ILIM

1.033

ILIM

52640V

OSmax

R

k

55960V

OSnom

R

k

56850V

OSmin

R

k

I

(mA) =

I

(mA) =

I

(mA) =

W

W

W

13

TPS25221

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SLVSDT3D – JANUARY 2018 – REVISED DECEMBER 2019

Product Folder Links: TPS25221

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Copyright © 2018–2019, Texas Instruments Incorporated

Feature Description (continued)

The open-drain fault reporting output FAULT is asserted (active low) immediately during an over-temperature

shutdown condition.

9.4 Device Functional Modes

Table 1. Protection Function Table

EVENT

CONDITION

ACTION

Overload on OUT

ILOAD > IOS

The device outputs IOS x RLOAD until thermal shutdown. The

fault indicator asserts when the over-current condition

persists for more 8 ms, the fault does not de-assert until

over-current is removed and persists for 8 ms.

Overheating

TJ > 165 C

The device immediately shuts off the internal power switch

and the fault indicator asserts immediately when the junction

temperature exceeds 165°C (typical). The device has a

thermal hysteresis of 20°C (typical). The fault indicator de-

asserts when the junction temperature falls below 145°C

(typical).

Undervoltage on IN

VIN < 2.37 V

The device immediately shuts off the internal current-limited

switch.

9.5 Programming

9.5.1 Programming the Current-Limit Threshold

The over-current threshold is user programmable through an external resistor. The TPS25221 uses an internal

regulation loop to provide a regulated voltage on the ILIM pin. The current-limit threshold is proportional to the

current sourced out of ILIM. The recommended 1% resistor range for RILIM is 20 kΩ ≤ RILIM ≤ 210 kΩ to ensure

stability of the internal regulation loop. Many applications require that the minimum current limit is above a certain

current level or that the maximum current limit is below a certain current level, so it is important to consider the

tolerance of the over-current threshold when selecting a value for RILIM. The following equations and Figure 24

can be used to calculate the resulting over-current threshold for a given external resistor value (RILIM). Figure 24

includes current-limit tolerance due to variations caused by temperature and process. However, the equations do

not account for tolerance due to external resistor variation, so it is important to account for this tolerance when

selecting RILIM. The traces routing the RILIM resistor to the TPS25221 must be as short as possible to reduce

parasitic effects on the current-limit accuracy.

RILIM can be selected to provide a current-limit threshold that occurs: 1) above a minimum load current or 2)

below a maximum load current.

To design above a minimum current-limit threshold, find the intersection of RILIM and the maximum desired load

current on the IOS(min) curve and choose a value of RILIM below this value. Programming the current limit above a

minimum threshold is important to ensure start-up into full load or heavy capacitive loads. The resulting

maximum current-limit threshold is the intersection of the selected value of RILIM and the IOS(max) curve.

To design below a maximum current-limit threshold, find the intersection of RILIM and the maximum desired load

current on the IOS(max) curve and choose a value of RILIM above this value. Programming the current limit below a

maximum threshold is important to avoid current limiting upstream power supplies, causing the input voltage bus

to droop. The resulting minimum current-limit threshold is the intersection of the selected value of RILIM and the

IOS(min) curve.

Current-Limit Threshold Equation (IOS):

where:

20 kΩ ≤ RILIM ≤ 210 kΩ.

(1)