Datasheet

SLUU087B
2
10-Watt Flyback Converter Using the UCC3809
1 Introduction
1.1 Design Procedure
The UCC3809EVM evaluation module is an isolated 10-W, 3.3-V converter designed for telecom input voltages,
nominally –48 Vdc but ranging from –32 Vdc to –75 Vdc. The UCC3809 economy primary-side controller is used
as the pulse-width modulator (PWM), combined with a TLV431 low-voltage adjustable-precision shunt regulator
on the secondary side. The nominal switching frequency for this converter is approximately 400 kHz. The
UCC3809 is configured with a 50% duty-cycle clamp.
1.2 Operating Specifications
SPECIFICATION MIN TYP MAX UNITS
Input voltage range 32 48 75 V
Output voltage range 3.218 3.3 3.383 V
Output current range 0 3.3 A
Operating frequency 344 380 420 kHz
Output ripple 100 mV
Efficiency (V
IN
= 48 V, I
OUT
= 3 A) 75 %
The circuit, shown in Figure 1, is a discontinuous fixed-frequency current-mode controlled flyback converter.
This converter contains features such as external shut down, optocoupler isolation, programmable maximum
duty cycle, and a summing node for voltage feedback, current sense, and slope compensation.
Table 1. UCC3809 10-W Flyback Converter Bill of Materials
Reference QTY Description Manufacturer Part Number
C1 1 Ceramic, 39 pF, ±5%, 50 V, NPO, 0603 Panasonic ECJ–1VC1H390J
C2 1 Ceramic, 1.0 µF, +80%/–20%, 50 V, Y5V, 0805 Taiyo Yuden UMK212F105ZG
C3 1 Ceramic, 10 nF, ±10%, 50 V, X7R, 0603 Panasonic ECU–V1H103KBV
C4 1 Ceramic, 0.47 µF, +80%/–20%, 16 V, Y5V, 0603 Panasonic ECJ–1VF1C474Z
C5 1 Ceramic, 10 µF, ±10%, 35 V, Y5V, 1210 Taiyo Yuden GMK325F106ZH
C6 1 Ceramic, 4.7 nF, ±10%, 50 V, X7R, 0603 Panasonic ECU–V1H472KBV
C7 1 Ceramic, 120 pF, ±5%, 50 V, NPO, 0603 Panasonic ECJ–1VC1H121J
Capacitor
C8 1 Ceramic, 1.5 nF, ±10%, 50 V, X7R, 0603 Panasonic ECU–V1H152KBV
Capacitor
C9
1 Ceramic, 150 pF, ±5%, 50 V, NPO, 0603 Panasonic ECU–V1H151JCV
C10, C11, C12 3 Tantalum, 470 µF, ±10%, 6.3 V, 7343H Kemet T510X477K006AS *
C13 1 Ceramic, 47 pF, ±5%, 50 V, NPO, 0603 Panasonic ECJ–1VC1H470J
C14 1 Ceramic, 10 µF, ±10%, 6.3 V, X5R, 1206 Taiyo Yuden JMK316BJ106ML
C15 1 Ceramic, 0.1 µF, +80%/–20%, 16V, Y5V, 0603 Panasonic ECJ–1VF1C104Z
C16, C17 2 Ceramic, 220 pF, ±5%, 50 V, NPO, 0603 Panasonic ECU–V1H221JCV
C18 1 Ceramic, 1 µF, ±10%, 100 V, X7R, 2225 Kemet C2225C105K1RAC *
C19 1 Ceramic, 1 µF, ±10%, 16 V, X7R, 1206 Panasonic ECJ–3YB1C105K
NOTE: * Equivalent substitution not recommended