HCF1305-2R2-R datasheet(22/39 Pages) MICROCHIP

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MIC24054

DS20007043B-page 22



2025-2026 Microchip Technology Inc. and its subsidiaries

If the voltage divider resistors R1 and R2 are in the kΩ

range, a CFF of 1 nF to 100 nF can easily satisfy the

large time constant requirements. Also, a 100 nF

injection capacitor Cinj is used in order to be

considered as short for a wide range of the

frequencies.

The process of sizing the ripple injection resistor and

capacitors is:

Step 1. Select CFF to feed all output ripples into the

Feedback pin and make sure the large time constant

assumption is satisfied. Typical choice of CFF is 1 nF to

100 nF if R1 and R2 are in the kΩ range.

Step 2. Select Rinj according to the expected feedback

voltage ripple using Equation 5-17:

EQUATION 5-19:

Then the value of Rinj is obtained as:

EQUATION 5-20:

Step 3. Select Cinj as 100 nF, which could be

considered as short for a wide range of the

frequencies.

5.5

Setting Output Voltage

The MIC24054 requires two resistors to set the output

voltage as shown in Figure 5-4.

FIGURE 5-4:

Voltage Divider

Configuration.

It is recommended to use a bleeder resistor (VOUT to

GND) of 27 kΩ for better regulation at output voltages

below 1V.

The output voltage is determined by Equation 5-21:

EQUATION 5-21:

If R1 is too large, it may allow noise to be introduced

into the voltage feedback loop. If R1 is too small, it will

decrease the efficiency of the power supply, especially

at light loads. Once R1 is selected, R2 can be

calculated using Equation 5-22.

EQUATION 5-22:

In addition to the external ripple injection added at the

FB pin, internal ripple injection is added at the inverting

input of the comparator inside the MIC24054, as shown

in Figure 5-5. The inverting input voltage VINJ is

clamped to 1.2V. As VOUT is increased, the swing of

VINJ will be clamped. The clamped VINJ reduces the

line regulation because it is reflected as a DC error on

the FB terminal. Therefore, the maximum output

voltage of the MIC24054 should be limited to 5.5V to

avoid this problem.

FIGURE 5-5:

Internal Ripple Injection.

KDIV

VFB PP







VIN

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

fSW 



1 D

–







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



Rinj

R1//R2





KDIV

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

–











VOUT VFB 1 R1

-------











VFB R1



VOUT VFB

–

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

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