MCP16413 datasheet(24/44 Pages) MICROCHIP

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MCP1641X

DS20006394D-page 24

 2020-2021 Microchip Technology Inc. and its subsidiaries

FIGURE 5-4:

PGT Output Response.

5.3.10

AUTOMATIC INPUT-TO-OUTPUT

BYPASS MODE

The MCP1641X features Automatic Input-to-Output

Bypass mode if VIN is close to the selected VOUT or

higher. In this situation, VOUT tracks VIN, which is

“bypassed” to the output through the synchronous

P-Channel MOSFET. The device resumes Boost mode

if VOUT decreases down to approximately 90% of the

target regulation voltage.

This function has the advantage of offering a highly

efficient Conversion mode while the battery is fresh,

which translates into better battery utilization. This mode

of operation also removes the high output ripple and

noise, which is usually present in boost converters

during operation when the value of the input is very close

to the desired output voltage (where the switching duty

cycle is minimum and limited). This mode is

recommended for noise-sensitive power rail applications

(e.g., audio, LCD displays). The disadvantage is that the

output is not regulated in this range, but equal with

battery voltage minus a drop on the synchronous

P-MOS (IOUT * RDSON) rectifier.

FIGURE 5-5:

Automatic Boost-Bypass

Transition.

5.3.11

ENABLE

The MCP1641X devices are enabled when the EN pin

is set high and are disabled when the EN pin is set low

(Shutdown mode). The enable threshold voltage varies

with the input voltage. To enable the boost converter,

the EN voltage level must be greater than 82% of the

VIN voltage. To disable the boost converter, the EN

voltage must be less than 25% of the VIN voltage.

In Shutdown mode, a low quiescent current, 2.3 µA

(typical), is consumed from the input (battery).

5.3.12

SHORT-CIRCUIT PROTECTION

Unlike most boost converters, the MCP1641X allows its

output to be shorted during normal operation. The 1A

(typical) internal current limit and thermal shutdown

reduce excessive stress and protect the device during

periods of short-circuit, overcurrent and overtemperature.

5.3.13

INPUT OVERCURRENT LIMIT

The MCP1641X devices use a 1A (typical)

cycle-by-cycle inductor peak current limit to protect the

N-Channel switch. The overcurrent comparator resets

the driving latch when the peak of the inductor current

reaches the limit. In current limitation, the output

voltage starts dropping. To assure highest load current

operation, by design, the current limit is higher than

typical for an input voltage close to the output voltage

value.

5.3.14

THERMAL SHUTDOWN

Thermal shutdown circuitry is integrated in the

MCP1641X devices. This circuitry monitors the

device’s junction temperature and shuts off the output

if the junction temperature exceeds the typical +140°C

value. If this threshold is exceeded, the device auto-

matically restarts once the junction temperature drops

by 10°C (typical).

PGT

RESPONSE

PGT

DELAY

VOUT

PGT

250 µs

<150 µs

VOUT (BOOST)

VOUT = (VIN –IOUT * RDSON)

VIN

VOUT

Time

VOUT = VIN

90% VOUT

0.85V

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