AS1313 datasheet(11/26 Pages) AMSCO

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ams Datasheet

Page 11

[v1-43] 2015-Jul-23

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AS1313 − Detailed Description

The AS1313 is a hysteretic converter and has no continuously

operating fixed oscillator, providing an independent timing

reference. This means the triggering of the on-off switching of

the internal switches depends only on comparators measuring

the output voltage and the coil current measurement. This lead

to a very low quiescent current. In addition, because there is no

fixed timing reference, the operating frequency is determined

by external components (inductor and capacitors) and the

loading on the output.

Ripple at the output is an essential operating behavior. A power

cycle is initiated when the output regulated voltage drops

below the nominal value of VOUT.

Figure 13:

Simplified Synchronous Step-Down DC-DC Architecture

When SW1 is closed and SW2 is open, the current is flowing from

VIN through the coil to RLOAD. With neglecting the resistive

voltage drop over SW1 the voltage across the coil is:

Based on the expression, which shows the correlation between

voltage across the coil and the coil current, it's easy to rearrange

this equation to get the coil current ICOIL generated while SW1

is closed (tON).

Detailed Description

SW2

SW1

GND

VIN

VOUT

VCOIL_on

VCOIL_off

ICOIL_on

ICOIL_off

VIN

VOUT

CIN

COUT

RLOAD

IPK

IZERO

VCOIL on

–

VIN VOUT

–

(EQ1)

-----

ICOIL



VIN VOUT

–

------------------------------ t

⋅





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