MP1601 Rev. 1.0

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15

3/24/2016

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HS_ driver

VREF

VFB

COT

Generator

EN

IAAM

IL_ sense

R

SQ

FBCOMP

AAMCOMP

Figure 5: Simplified AAM Control Logic

The AAM comparator pulse is shorter than the

on-time generator. The mode of operation is

shown below in Figure 7. This usually occurs

when using a very small inductance.

Besides the upper on-time method, the AAM

circuit has another 150ns AAM blank time in

sleep mode. If the on-timer is less than 150ns,

the high-side MOSFET may turn off after the

on-time generator pulse without AAM control.

The on-time pulse at sleep mode is around 40%

larger than that in DCM or CCM. In this

(see Figure 8).

Figure 8: AAM Blank Time in Sleep Mode

Figure 9 shows the AAM threshold decreasing

threshold.

Increasing

The MP1601 uses ZCD to detect if the inductor

current begins reversing. When the inductor

current reaches the ZCD threshold, the low-side

switch is turned off.

AAM mode and the ZCD circuit together cause

the MP1601 to work in DCM in light load

Enable (EN)

When the input voltage is greater than the

under-voltage

lockout

(UVLO)

threshold

(typically 2V), the MP1601 can be enabled by

pulling EN higher than 1.2V. Floating EN or

pulling it down to ground disables the MP1601.

There is an internal 1MΩ resistor from EN to

ground.

When the device is disabled, the MP1601 goes

into output discharge mode automatically. Its

internal discharge MOSFET provides a resistive

discharge path for the output capacitor.

Soft Start (SS)

The MP1601 has a built-in soft start that ramps

up the output voltage at a controlled slew rate

to avoid overshooting at start-up. The soft start

time is about 0.5ms, typically.