MIC2133 datasheet(30/50 Pages) MICROCHIP

30 / 50 page

 2022 Microchip Technology Inc. and its subsidiaries

DS20006653B-page 30

MIC2133

RDSON(LS) increases to about 2x, at 125°C related to

the value at 25°C; therefore, it is necessary to choose

RDSON *IOUT(MAX) < 60 mV at 25°C to respect the

sensing range over temperature.

To desensitize the AVP related to the temperature

variation of RDSON, a resistance network used with an

NTC resistor needs to be used, as shown in the figure

below.

FIGURE 4-20:

Use of an NTC Resistance

to Compensate the RDSON Temperature

Coefficient on the DROOP Pin.

The idea in the figure above is that increasing the

DROOP voltage with temperature at the IOUT(MAX)

(positive temperature coefficient) is compensated by

the RNTC (negative temperature coefficient) to keep the

node of the divider, Div_DROOP_ZeroTC, constant

versus temperature.

The rest of the calculations are similar to the afore-

mentioned case, where the sensing current was

temperature-insensitive. In case the AVP is not neces-

sary, a 10 kΩ, 1 nF series RC filter to ground can be used

to have a reading of the filtered output current.

4.5.12

OVP FUNCTION

The MIC2133 operates with high input voltages

powering costly ASIC or PA. If the high-side MOSFET

is damaged during switching, it can present high output

voltage which can damage the costly load. This can

also happen if the FB path is open during the assembly

process, which in turn, can damage the costly load

while testing.

To discharge the output during those high output volt-

age Fault conditions, the MIC2133 has a dedicated DR

pin with a discharge FET driver.

The threshold for this OVP comparator is programmed

internally at 112% of the reference voltage. An external

discharge FET is connected from VOUT, in case of

faulty conditions, to provide a short path for a high cur-

rent. A series resistor can be connected to limit a high

short current.

The DR pin is latched in high if an overvoltage of a

duration longer than 12 µs typical is present on the out-

put. All the overvoltage events that last less than 12 µs

will not trigger DR = High. The circuitry involving OVP

will be active after the rise threshold of UVLO before

any other action of the control loop.

To reset the state of DR = High latched, it is necessary

to make UVLO go low, which means to collapse the

VDD rail. This Reset action can be obtained by making

EN = Low and waiting for VDD to collapse. Another

possible Reset action is shutting down the input VIN, in

which case the VDD will collapse because of the

HVLDO linear regulator.

The external FET can pull down the EN pin tied to VIN

with a resistor. In this case, it is possible to have a very

long time until the VDD collapses and the UVLO resets

the DR output. In this case, a very long time cycle will

take place after the part restarts. The DR pin can be

reset either by VIN cycling or EN cycling.

Another possible protection during OVP is to use the

DR output to make an SCR on, and fire a fuse on the

VIN power supply, disconnecting the input power

supply from the buck converter.

4.5.13

TELEMETRY KNOBS

The MIC2133 can provide die temperature and

average output current sense outputs. These analog

outputs can be used by the PMBus-enabled micro-

controller to convert to digital form and communicate

with the PMBus host for telemetry. The MIC2133 to

PMBus-enabled microcontroller connections are illus-

trated in the figure below.

FIGURE 4-21:

MIC2133 to PMBus-Enabled

Microcontroller Connections.

The MIC2133 die temperature is monitored internally

across the PN junction diode and provided as voltage

at the TEMP pin. A 1 µF capacitor is connected at

TEMP to AGND to remove the DC error.

The internal temperature sense has a 6 mV/°C gain

and a 1.8V offset voltage. The internal temperature

sense can be reported from -40°C to +125°C to the

PMBus enabled microcontroller.

MIC2133

FBS

DROOP

VOUT

RINJ

CINJ

RIP_INJ

GFB

RDROOP

RFBT

CFF

RNTC

Div_DROOP_ZeroTC

RBIAS

RFBB1

RFBB2

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