XR76203-Q/XR76205-Q/XR76208-Q

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exar.com/XR76203-Q/XR705-Q/XR76208-Q

Rev 1C

©2016-2017 Exar Corporation

Programming the On-Time

ing to following equation:

where:

Eff is the Regulator efficiency corresponding to nominal

Over-Current Protection (OCP)

for four consecutive switching cycles, the Module enters

hiccup mode of operation. In hiccup, the MOSFET gates

are turned off for 110ms (hiccup timeout). Following the hic-

cup timeout, a soft-start is attempted. If OCP persists, hic-

cup timeout will repeat. The Module will remain in hiccup

mode until load current is reduced below the programmed

the following equation:

Where:

RDS is the MOSFET rated On Resistance; XR76208-

Q=21.5mΩ, XR76205-Q=59mΩ, XR76203-Q=59mΩ

8mV is the OCP comparator maximum offset

ILIM is the internal current that generates the necessary

OCP comparator threshold (use 45μA).

Note that ILIM has a positive temperature coefficient of

0.4%/°C (figure 10). This is meant to roughly match and

compensate for positive temperature coefficient of the syn-

in figure 7-9. Maximum allowable RLIM for XR76205-Q is

8.06kΩ.

Short-Circuit Protection (SCP)

If the output voltage drops below 60% of its programmed

value, the Module will enter hiccup mode. Hiccup will per-

sist until short-circuit is removed. SCP circuit becomes

active after PGOOD asserts high.

Over-Temperature (OTP)

OTP triggers at a nominal die temperature of 150°C. The

gate of switching FET and synchronous FET are turned off.

When die temperature cools down to 135°C, soft-start is

initiated and operation resumes.

Programming the Output Voltage

Use an external voltage divider as shown in the Application

where R2 has a nominal value of 2kΩ.

Programming the Soft-start

Place a capacitor CSS between the SS and AGND pins to

program the soft-start. In order to program a soft-start time

of TSS, calculate the required capacitance CSS from the

following equation:

R

ON

9

–

10



–





3.05

10

–

10

------------------------------------------------------------

=

T

ON





-------------------------------

=

R

ON

fEff



----------------





25

9

–

10

 V

IN





–

3.05

10

–

10

-------------------------------------------------------------------------

=

RLIM



 8mV

+

ILIM

----------------------------------------------------

=

R1

R2

0.6

------------- 1

–







=

CSS

TSS

10

A

0.6V

--------------







=