2.13 Transformer Design

The internal switch dc-dc (Si8281, Si8283) and external switch dc-dc (Si8282, Si8284) operate in different topologies and, thus, require

different transformer designs. The table below provides a list of transformers and their parametric characteristics that have been valida-

ted to work with Si828x products. It is recommended that users order the transformers from the vendors per the part numbers given

below.

To manufacture transformers from your preferred suppliers that may not be listed below, please specify to supplier the parametric char-

acteristics as specified in the table below for a given input voltage and isolation rating.

Table 2.2. Si828x Recommended Transformers

Transformer Supplier

Ordering Part #

Input

Voltage

Turns Ratio

Leakage

Inductance

Primary

Inductance

Primary

Resistance

Isolation

Rating

UMEC

www.umec-usa.com

UTB02257s

3.0–5.5 V

1:15:5

125 nH max 1.5 µH ± 5% 0.05 Ω max

5 kV

UTB02241s

4.5–5.5 V

1:9:33.667

100 nH max

2 µH ± 5%

0.05 Ω max

5 kV

UTB02253s

7–24 V

1.2:1.21

200 nH max 25 µH ± 5% 0.225 Ω max

5 kV

Coilcraft

www.coilcraft.com

TA7788-AL

7–24 V

1:1.25:0.75

550 nH max 25 µH ± 5% 0.460 Ω max

5 kV

Si8281/82/83/84 Data Sheet

System Overview

silabs.com | Smart. Connected. Energy-friendly.

Preliminary Rev. 0.5 | 10