AS3607 datasheet(17/71 Pages) AMSCO

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AS3606 AS3607 2v2

Data Sheet - D e t a i l e d D e s c r i p t i o n - P o w e r M anage ment F uncti ons

8.2.1 Functional Description

The step-down converter is a high efficiency fixed frequency current mode regulator. By using low resistance internal PMOS and NMOS switches

efficiency up to 97% can be achieved. The fast switching frequency allows using small inductors, without increasing the current ripple. The

unique feedback and regulation circuit guarantees optimum load and line regulation over the whole output voltage range, up to an output current

of 700mA, with an output capacitor of only 10µF. The implemented current limitation protects the DCDC and the coil during overload condition.

To achieve optimized performance in different applications, adjustable settings allow to compromise between high efficiency and low input,

output ripple:

Low Ripple, Low Noise Operation (current force mode = OFF). In this mode there is no minimum coil current necessary before

switching off the PMOS. As result, the ON time of the PMOS will be reduced down to tmin_on at no or light load conditions, even if the coil

current is very small or the coil current is inverted. This results in a very low ripple and noise, but decreased efficiency, at light loads, especially at

low input to output voltage differences. In the case of an inverted coil current the regulator will not operate in pulse skip mode.

Figure 7. DCDC Buck with Disabled Current Force / Pulse Skip Mode

High Efficiency Operation (current force mode = ON). In this mode, there is a minimum coil current necessary before switching off the

PMOS. As result, fewer pulses at low output loads are necessary, and therefore the efficiency at low output load is increased. On the other hand

the output voltage ripple increases, and the noisy pulse skip operation is on up to a higher output current.

Figure 8. DCDC Buck with Enabled Current Force / Pulse Skip Mode

It’s also possible to switch between these two modes dynamically during operation.

1: LXC1 voltage

2: Coil current (1mV=1mA)

3: Output voltage

1: LXC1 voltage

2: Coil current (1mV=1mA)

3: Output voltage

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