MP2192

– 2A, SYNCHRONOUS STEP-DOWN CONVERTER WITH 25µA IQ

MP2192 Rev. 1.0

MonolithicPower.com

14

5/12/2021

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© 2021 MPS. All Rights Reserved.

HS Driver

VREF

VFB

COT

Generator

EN

IAAM

IL_SENSE

R

S

Q

FBCOMP

AAMCOMP

Figure 5: Simplified AAM Control Logic

Under light-load conditions, the SW on-pulse

time is the longer pulse. If the AAM comparator

pulse is longer than the on-time generator, the

operation mode is controlled by AAM (see

Figure 6).

AAM

IOUT

IL

b. Increasing Load in AAM

AAM

IOUT

IL

a. Light Loads in AAM

Figure 6: The AAM Comparator Controls tON

If the AAM comparator pulse is shorter than the

on-time generator, the operation mode

is

controlled by the on-time generator (see Figure

7).

AAM

IOUT

IL

b. Increasing Loads with On-Timer

AAM

IOUT

IL

a. Light Loads with On-Timer

Figure 7: The On-Timer Controls tON

Figure 8 shows that when the AAM threshold

decreases, tON increases gradually. For CCM,

IOUT must exceed at least 50% of the AAM

threshold. Generally, the AAM threshold is

below the inductor current during normal duty

cycles.

The MP2192 uses ZCD to determine if the

inductor current has started reversing. When

the inductor current reaches the ZCD threshold,

the LS-FET turns off.

AAM with a ZCD circuit forces the MP2192 to

work in DCM under light loads, even if VOUT is

close to VIN.

0

50

100

150

200

250

300

350

0

0.5

1

1.5

2

2.5

3

Ton(µs)

AAM Threshold vs. Ton

Figure 8: AAM Threshold Decreases as tON

Increases

Enable (EN)

If the input voltage exceeds the under-voltage

lockout (UVLO) threshold (typically 2.3V), the

MP2192 can be enabled by pulling EN above

1.2V. Leave EN floating or pull EN down to

ground to disable the MP2192. There is an

internal 1M

Ω resistor connected from EN to

ground.

When the device is disabled, the part enters

output

discharge

mode

automatically.

The

device

’s internal discharge MOSFET provides a

resistive

discharge

path

for

the

output

capacitor.

Soft Start (SS)

The MP2192 has 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 1.1ms.

Current Limit

The MP2192 has a typical 3.5A HS-FET current

limit. When the high-side switch reaches its

current limit, the MP2192 remains in hiccup

mode until the current drops. This prevents the

inductor current from continuing to rise and

damaging components.

Short Circuit and Recovery

The MP2192 triggers short-circuit protection

(SCP) when it reaches its current limit and

attempts to recover with hiccup mode. The

MP2192 disables the output power stage,

discharges

the

soft-start

capacitor,

and

attempts soft start again automatically. If the

short-circuit condition remains after soft start

ends, the MP2192 repeats this cycle until the

1.5

tON (μS)

AAM Threshold vs. tON