Page 12

ams Datasheet

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[v1-43] 2015-Jul-23

AS1313 − Detailed Description

When SW1 is open and SW2 is closed, the coil gets discharged,

works like a voltage supply and forces the current through

SW2 the voltage across the coil is:

The increasing coil current during the charging (SW1 closed)

and the decreasing coil current during the discharging of the

coil (SW2 closed) must be the same. Hence, it’s easy to calculate

the duty cycle of SW1.

Based on the EQ1, the on time of SW1 can be given by:

Figure 14:

Simplified Voltage and Current Diagram

Timing Diagram: This figure shows the relationship between the current and the voltages inside the loop within

the switching cycle.

–

=

(EQ2)

L

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

OFF

⋅

=

(EQ3)

–

L

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

ON

⋅

L

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

OFF

⋅





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

+

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

=







==

(EQ4)

L

–

------------------------------ I

COIL

⋅

=

t

0

0

V

I

C

A

B

B

A

D

t

400mA

SW1 on

SW2 off

SW1 off

SW2 on

SW1 off

SW2 off

SW1 on

SW2 off

SW1 off

SW2 on