AMC3202DMF

APPLICATION SUMMARY

The

AMC3202 incorporates a current mode control scheme, in which the duty cycle of the

switch is directly controlled by switch current rather than by output voltage. The output of

the oscillator turns on the power switch at a frequency of 280kHz as shown in the block

diagram. The power switch is turned off by the output of the PWM comparator.

A TTL low voltage will shut down the chip and high voltage enable the chip through

EN pin. This pin may also be used to synchronize the part to nearly twice the base

oscillator frequency. In order to synchronize to a higher frequency, a positive transition

turns on the power switch before the output of the oscillator goes high, thereby resetting

the oscillator. The synchronization operation allows multiple power supplies to operate at

the same frequency. If synchronization is not used,this pin should be either tied high or

left floating for normal operation.

Component Selection:

The

AMC3202 develops a 1.276V reference from the FB pin to ground. Output voltage is

set by connecting the FB pin to an output resistor divider and the maximum output voltage

is determined by the VSW pin maximum voltage minus the output diode forward voltage.

Referring to typical application circuit, the output voltage is set by the below formula(1):

When choosing the inductor, one must consider factors such as peak current, core and

ferrite material, output voltage ripple, EMI, temperature range, physical size, and cost.

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AMC3202DMF