PI5USB2546 datasheet(27/31 Pages) DIODES

27 / 31 page

All trademarks are property of their respective owners.

www.diodes.com

1/18/2017

2016-11-0004

PT0493-4

PI5USB2546

Current-Limit Settings

The PI5USB2546 have two independent current limit settings that are each programmed externally with a resistor. The

ILIM_HI setting is programmed with RILIM_HI connected between ILIM_HI and GND. The ILIM_LO setting is programmed

with RILIM_LO connected between ILIM_LO and GND. Consult the Device Truth Table to see when each current limit is used.

Both settings have the same relation between the current limit and the programming resistor. RILIM_LO is optional and the

ILIM_LO pin may be left unconnected if the following conditions are met:

ILIM_SEL is always set high

Load Detection - Port Power Management is not used

The following equation programs the typical current limit:

IOS_TYP (mA)=50250/RLIM_xx (kΩ)

RILIM_XX corresponds to either RILIM_HI or RILIM_LO as appropriate.

Many applications require that the current limit meet specific tolerance limits. When designing to these tolerance limits, both

the tolerance of the PI5USB2546 current limit and the tolerance of the external programming resistor must be taken into

account. The following equations approximate the PI5USB2546 minimum / maximum current limits to within a few mA and

are appropriate for design purposes. These equations assume an ideal – no variation - external programming resistor. To take

resistor tolerance into account, first determine the minimum /maximum resistor values based on its tolerance specifications and

use these values in the equations. Because of the inverse relation between the current limit and the programming resistor, use

the maximum resistor value in the IOS_MIN equation and the minimum resistor value in the IOS_MAX equation.

IOS_MIN (mA)=45271/(RLIM_xx (kΩ))

0.98437-30

IOS_MAX (mA) =55325/ (RLIM_xx (kΩ))

1.0139+30

The traces routing the RILIM_XX resistors should be a sufficiently low resistance as to not affect the current-limit accuracy. The

ground connection for the RILIM_XX resistors is also very important. The resistors need to reference back to the PI5USB2546

GND pin. Follow normal board layout practices to ensure that current flow from other parts of the board does not impact the

ground potential between the resistors and the PI5USB2546 GND pin.

/FAULT Response

The /FAULT open-drain output is asserted (active low) when an over-temperature or current limit condition occurs. The

PI5USB2546 is designed to eliminate false /FAULT reporting by using an internal deglitch circuit for current limit conditions

without the need for external circuitry. This ensures that /FAULT is not accidentally asserted due to normal operation such as

starting into a heavy capacitive load. Over-temperature conditions are not deglitched and assert the /FAULT signal immediately.

Undervoltage Lockout (UVLO)

The undervoltage lockout (UVLO) circuit disables the power switch until the input voltage reaches the UVLO turn on threshold.

Built-in hysteresis prevents unwanted oscillations on the output due to input voltage drop from large current surges.

PI5USB2546 Fiches technique(PDF) 27 Page - Diodes Incorporated