MIC24046 datasheet(21/38 Pages) MICROCHIP

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2022 Microchip Technology Inc.

DS20006677A-page 21

MIC24046

5.2

Setting the Switching Frequency

The MIC24046 switching frequency can be pro-

grammed using the FREQ pin as shown in Table 5-1:

5.3

Setting the Output Voltage

The MIC24046 output voltage can be programmed by

setting pins VOSET0 and VOSET1, as shown in

Table 5-2.

To achieve accurate output voltage regulation, the

OUTSNS pin (internal feedback divider top terminal)

should be Kelvin-connected as close as possible to the

point-of-regulation top terminal. Since both the internal

reference and the internal feedback divider’s bottom

terminal refer to AGND, it is important to minimize volt-

age drops between the AGND and the point-of-regula-

tion return terminal.

5.4

Setting the Current Limit

The MIC24046 valley-mode current limit on the

low-side MOSFET can be programmed by means of

ILIM pin as shown in Table 5-3.

Note that the programmed current-limit values act as

pulse-by-pulse current-limit thresholds on the valley

inductor current. If the inductor current has not decayed

below the threshold at the time the PWM requires a

new ON time, the high-side MOSFET turn-on is either

delayed until the valley current recovers below the

threshold or skipped. Each time the high-side MOSFET

turn-on is skipped, a 4-bit up-down counter is incre-

mented. When the counter reaches the configuration

1111, a hiccup sequence is invoked in order to reduce

power dissipation under prolonged short-circuit condi-

tions.

The highest current-limit setting (6.8A) is intended to

comfortably accommodate a 5A application.

Ensure the value of the operating junction temperature

does not exceed the maximum rating in high output

power applications.

5.5

Inductor Selection and Slope

Compensation

When selecting an inductor, it is important to consider

the following factors:

• Inductance

• Rated current value

• Size requirements

• DC resistance (DCR)

• Core losses

The inductance value is critical to the operation of

MIC24046. Because the MIC24046 is a valley cur-

rent-mode regulator, it needs a slope compensation for

the stable current loop operation where duty cycles are

below 50%. Slope compensation is internally pro-

grammed according to the frequency and output volt-

age selection, assuming there is a minimum

inductance value for the given operating condition.

Table 5-4 lists the assumed minimum inductor values

recommended for stable current loop operation. Note

that the minimum suggested inductance values should

be met when taking into account inductor tolerance and

its change with current level.

TABLE 5-1:

SWITCHING FREQUENCY

SETTINGS

FREQ

Frequency

Hi-Z (Open)

400 kHz

0 (GND)

565 kHz

1 (VDDA)

790 kHz

TABLE 5-2:

OUTPUT VOLTAGE

SETTINGS

VOSET1

VOSET0

Output Voltage

0 (GND)

3.3V

0 (GND)

1 (VDDA)

2.5V (2.49V)

1 (VDDA)

0 (GND)

1.8V

1 (VDDA)

1.5V

0 (GND)

Hi-Z (Open)

1.2V

Hi-Z (Open)

0 (GND)

1.0V

1 (VDDA)

Hi-Z (Open)

0.9V

Hi-Z (Open)

1 (VDDA)

0.8V

Hi-Z (Open)

0.7V

TABLE 5-3:

CURRENT-LIMIT SETTING

ILIM

Low-Side Valley

Current Limit

(Typical Value)

Rated Output

Current

0 (GND)

4.6 A

1 (VDDA)

6.2 A

Hi-Z (Open)

6.8 A

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