MIC33M350 datasheet(17/32 Pages) MICROCHIP

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DS20006348B-page 17

MIC33M350

4.0

DETAILED DESCRIPTION

4.1

Device Overview

The MIC33M350 device is a high-efficiency, 3A current,

synchronous buck regulator power module with inte-

grated inductor. The COT control architecture with

automatic HyperLight Load mode provides very high

efficiency at light loads and ultra-fast transient

response.

The MIC33M350 output voltage is set by two VSEL

three-state logic pins that can set the output voltage to

nine different values (see Table 4-1).

The 2.4V to 5.5V input voltage operating range makes

the device ideal for single cell Li-ion battery-powered

applications. The 100% duty cycle capability provides

Low Dropout operation, extending battery life in

portable systems. The automatic HyperLight Load

mode provides very high efficiency at light loads.

These devices focus on high output voltage accuracy.

Total output error is less than 1.5% over line, load and

temperature.

MIC33M350 focuses on high output voltage accuracy.

The MIC33M350 buck regulator uses an adaptive

Constant On-Time control method. The adaptive

on-time control scheme is employed to obtain a nearly

constant switching frequency and to simplify the control

compensation. Overcurrent protection is implemented

without the use of an external sense resistor. The

MIC33M350 device includes an internal soft start

function which reduces the power supply input surge

current at start-up by controlling the output voltage rise

time.

4.2

HyperLight Load® Mode (HLL)

HLL is a power-saving mode. In HLL, the switching

frequency is not constant over the operation current

range. At light loads, the minimum duty cycle is limited,

which causes the switching frequency to decrease at

light loads, this reduces switching and drive losses, and

increases efficiency.

4.3

Enable (EN)

When the EN pin is pulled low, the IC is in a Shutdown

state, with all internal circuits disabled and with the

Power Good output low. During shutdown, the

MIC33M350 part typically consumes 1.5 µA. When the

EN pin is pulled high, the start-up sequence is initiated.

4.4

Power Good (PG)

The Power Good output is generally used for power

sequencing, where the PG output is tied to the Enable

output of another regulator. This technique avoids all

the regulators powering up at the same time, which

causes large inrush current.

PG is an open-drain output that indicates that the

output is above 87% of its voltage set value. During

start-up, when the output voltage is rising, the Power

Good output goes high when the output voltage

reaches 91% of its set value. The Power Good

threshold has 4% hysteresis, so the Power Good

output stays high until the output voltage falls below

87% of the set value. A built-in 65 µs blanking time is

incorporated to prevent nuisance tripping.

A pull-up resistor can be connected to VIN, VOUT, or an

external source that is less than or equal to VIN. The

PG pin can be connected to another regulator’s enable

pin for sequencing of the outputs. The PG output is

deasserted as soon as the Enable pin is pulled low or

an input undervoltage condition, or any other Fault is

detected.

4.5

Resistive Discharge (Soft

Discharge)

To ensure a known output condition when the output is

turned off, then back on again (i.e. in a brown output

condition), the output is actively discharged to ground

by means of an internal 10

 resistor if the output is

disabled.

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