MIC2133 datasheet(26/50 Pages) MICROCHIP

26 / 50 page

 2022 Microchip Technology Inc. and its subsidiaries

DS20006653B-page 26

MIC2133

As shown in Example 4-2, the sizing of current limit per

phase needs to be verified over temperature to make

sure Equation 4-16 and Equation 4-17 work correctly,

because it is necessary to always have:

EQUATION 4-19:

For linearization and fitting the temperature coefficient

of the bottom MOSFET RDSON, a network from ILIM pin

to AGND, used with an NTC resistor, is shown in the

following figure.

FIGURE 4-12:

Resistance Network Used

with RNTC Resistor for Linearization and Fitting

the Temperature Coefficient of MOSFET RDSON.

In case a temperature-independent resistor sensing is

used, a simple temperature constant standard

resistance is used on the ILIM pin.

4.5.5

NEGATIVE CURRENT LIMIT

The MIC2133 supports a cycle-by-cycle negative cur-

rent limit. The absolute value of the negative

current-limiting threshold is 50% of the programmed

current limit. If the negative low-side MOSFET current

is going to trigger a negative current limit, the low-side

MOSFET will be turned off and allow current through its

body diode. During this time, the output voltage tends

to rise because this protection limits the current to dis-

charge the output capacitor. To prevent a huge reverse

current over the short limit value, the low-side FET

turns on after 500 ns, maintaining negative current at

the programmed level.

4.5.6

PRECISION ENABLE (EN)

The precision enable input (EN) is used to control the

regulator. The precision feature allows the simple

sequencing of multiple power supplies with a resistor

divider from another supply. Connecting this pin to

ground or to a voltage lower than 1.2V (typical) will turn

off the regulator. In this state, the current drain from the

input supply is 25 µA (typical) at a 12V input voltage.

The EN input has an internal pull-up of about 6 µA.

Therefore, this pin can be left floating or pulled to a volt-

age greater than 1.2V (typical) to turn the regulator on.

The hysteresis on this input is about 65 mV (typical)

above the 1.2V (typical) threshold. When driving the

enable input, the voltage must never exceed the abso-

lute maximum specification for this pin. Although an

internal pull-up is provided on the EN pin, it is a good

practice to pull the input high when this feature is not

used, especially in noisy environments. This can be

done easily by connecting a high-value resistor (1 MΩ)

between the VIN and EN pins. The MIC2133 device also

incorporates an internal input undervoltage lockout

(UVLO) feature. This prevents the regulator from turning

on when the input voltage is not high enough to properly

bias the internal circuitry. The rising threshold is 4.3V

(typical), while the falling threshold is 3.9V (typical). In

some cases, these thresholds may be too low to provide

good system performance. The solution is to use the EN

input as an external programmable input UVLO to dis-

able the part when the input voltage falls below a target

lower threshold. This is often used to prevent excessive

battery discharge or early turn-on during start-up. This

method is also recommended to prevent abnormal

device operation in applications where the input voltage

falls below the minimum of 4.5V. Figure 4-13 shows the

connections to implement this method of UVLO. The two

equations below can be used to determine the correct

resistor values.

EQUATION 4-20:

EQUATION 4-21:

Due to the 6 µA pull-up, the current in the divider must

be much higher than this. A value of 20 kΩ for RBOT is

a good first choice.

1.2V 4 RDSON



ILIM





RTOP

RBOT

VOFF

VENTH VENHYS

–

------------------------------------------ 1

–







Where:

RTOP = Top Resistor of the VIN Voltage Resistor

Divider

RBOT = Bottom Resistor of the VIN Voltage Resistor

Divider

VOFF = Target VIN Voltage below which the

Regulator turns off

VENTH = Device Enable Upper Threshold Voltage

VENHYS = Enable Threshold Hysteresis Voltage

VON

VOFF

VENTH

VENTH VENHYS

–

------------------------------------------



Where:

VOFF = Input Voltage where the Regulator

Shuts Off

VON = Input Voltage where the Regulator Turns On

VENHYST = Enable Threshold Hysteresis

VENTH = Enable Upper Threshold Voltage

MIC2133 датащи(PDF) 26 Page - Microchip Technology

MIC2133 датащи(HTML) 26 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

датащи скачать

ссылки URL