Buck Boost Converter Discussion

1:23

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Looking for "Table or figure of switching frequency selection resistor values; include 500 kHz or nearest" in tps552892.pdf?ts=1698770017628&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fen-us%252Fdocs%252Funiversalsearch.tsp%253FlangPref%253Den-US%2526searchTerm%253DTPS552892RYQR%2526nr%253D8

Looking for "FSW pin description and how switching frequency is set (RFSW), including any equation or table mapping RFSW to frequency" in tps552892.pdf?ts=1698770017628&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fen-us%252Fdocs%252Funiversalsearch.tsp%253FlangPref%253Den-US%2526searchTerm%253DTPS552892RYQR%2526nr%253D8

Looking for "Recommended connection for FSW pin (resistor to AGND?), and any allowable frequency range" in tps552892.pdf?ts=1698770017628&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fen-us%252Fdocs%252Funiversalsearch.tsp%253FlangPref%253Den-US%2526searchTerm%253DTPS552892RYQR%2526nr%253D8

Calculating.

Set the switching frequency on TPS552892RYQR by the FSW pin resistor:

Datasheet (Pin Functions, Table 5-1): the FSW pin switching frequency is programmed by a resistor between FSW and AGND.
Datasheet frequency equation (Eq. 3 / Section “Switching Frequency”):
$f_{SW} = \frac{1000}{0.05 \times R_{FSW} + 35}\ \text{(MHz)}$

For ~500 kHz target

Using the datasheet equation, RFSW ≈ 39.3 kΩ for fSW = 0.5 MHz (500 kHz).

Where to change it in the PSpice project

In the TI PSpice reference schematic, find the resistor that:

connects to the net/pin labeled FSW (pin 6), and
goes to AGND (often labeled something like R_FSW / RFSW / Rset)

Set that resistor to 39.2 kΩ (E96) or 39.0 kΩ (E24), depending on what you have available.

If you share a screenshot of the PSpice schematic around the FSW pin, I can point to the exact refdes to edit.

58 days

vtitanhardware

Image

58 days

flux

0:25

Analy.

Calculating.

In the schematic you shared, FSW is set by the resistor from the FSW pin down to AGND/ANAGND.

It’s the part labeled R164 (shown as 49.9 kΩ, 0402) connected directly to the FSW net (bottom-left of the IC) and to ANAGND/AGND.

To target ~500 kHz, change that resistor to 39.3 kΩ (E96; 39.2 kΩ is also a common pick).

So in your PSpice project: edit R164 value from 49.9 kΩ -> 39.3 kΩ.

Pull R164 to 400kHz

Check SW1/SW2 placement

Review decoupling issues

Verify PG/EN nets

Find 39.2k 0402

58 days

SW1

PGND_3

ISP

DITH/SYNC

CDC

EN/UVLO

AGND

BOOT2

COMP

VIN

SW2

PGND_2

FSW

BOOT1

EXTVCC

ISN

~CC

VCC

VOUT

MODE

PGND_1

Reviews

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