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SC453

Portable, VID Programmed Single Phase Power Supply Controller

Semtech Corporation 

SC453

POWER MANAGEMENT

Applications Information (Cont.)

SUPPLY, BIAS, UVLO, POWER GOOD GENERATOR

Supply

The chip is optimized to operate from a 5V ± 5% rail but

also designed to work up to 6V maximum supply voltage.

Under-Voltage Lock-Out Circuit

The Under-Voltage Lock-Out Circuit consists of compara-

tors which monitor the VCCA and V5 voltage levels. The

SC453 is in UVLO mode while either supply has not

ramped above the upper threshold or has dropped below

the lower threshold. During UVLO, the external FETs are

held off, tri-stating the output (DRN).

Over-Voltage Protection

If the CORE voltage is greater than +14% of the DAC (i.e.,

out of the power good window), the SC453 will latch off

and hold the low-side driver on permanently. Either the

power or EN must be recycled to clear the latch. The latch

is disabled during soft-start and VID/Sleep transitions.

For safety, the latch is enabled if the CORE voltage ex-

ceeds 2V even during VID/Sleep transitions.

Thermal Shutdown

The device will be disabled and latched off when the inter-

nal junction temperature reaches approximately 160°C.

Either the power or EN must be recycled to clear the

latch.

Band Gap Reference

A ± 0.85% precision Band Gap reference acts as the in-

ternal reference voltage standard of the chip, which all

critical biasing voltages and currents are derived from. All

references to VREF in the equations to follow will assume

VREF = 1.7V.

Precision DAC

This 6-bit digital-to-analog converter (DAC) serves as the

programmable reference source of the Core Comparator.

Programming is accomplished by logic voltage levels ap-

plied to the DAC inputs. The VID code vs. the DAC output

is shown in the following table. The accuracy of the VID

/DAC is maintained on the same level as the Band Gap

reference.

VID

54 32 10

000000

00000 1

0000 10

0000 11

000 100

000 10 1

000 110

000 111

00 1000

00 100 1

00 10 10

00 10 11

00 1100

00 110 1

00 1110

00 1111

0 10000

0 1000 1

0 100 10

0 100 11

0 10 100

0 10 10 1

0 10 110

0 10 111

0 11000

0 1100 1

0 110 10

0 110 11

0 11100

0 1110 1

0 11110

0 11111

VDAC

V

1.708

1.692

1.676

1.660

1.644

1.628

1.612

1.596

1.580

1.564

1.548

1.532

1.516

1.500

1.484

1.468

1.452

1.436

1.420

1.404

1.388

1.372

1.356

1.340

1.324

1.308

1.292

1.276

1.260

1.244

1.228

1.212

VID

54 3 2 10

10 0 0 0 0

10000 1

100 0 10

1000 11

100 100

100 10 1

100 110

100 111

10 1000

10 100 1

10 10 10

10 10 11

10 1100

10 110 1

10 1110

10 1111

1 10 00 0

1 10 00 1

1 10 0 10

1 10 0 1 1

1 10 10 0

1 10 10 1

1 10 1 10

1 10 1 1 1

1 1 10 0 0

11100 1

1 110 10

1110 11

1 11100

1 1110 1

1 11110

111111

VDAC

V

1.196

1.180

1.164

1.148

1.132

1.116

1.100

1.084

1.068

1.052

1.036

1.020

1.004

0.988

0.972

0.956

0.940

0.924

0.908

0.892

0.876

0.860

0.844

0.828

0.812

0.796

0.780

0.764

0.748

0.732

0.716

0.700

© 2006 Semtech Corp.

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