STR-W6735 Datasheet, PDF (1/14 Pages) Allegro MicroSystems – Quasi-Resonant Topology Primary Switching Regulators

STR-W6735
Quasi-Resonant Topology
Primary Switching Regulators
Features and Benefits
▪ Quasi-resonant topology IC ⇒ Low EMI noise and soft
switching
▪ Bottom-skip operation ⇒ Improved system efficiency
over the entire output load by avoiding increase of
switching frequency
▪ Standby burst mode operation ⇒ Lowers input power at
very light output load condition
▪ Avalanche-guaranteed MOSFET ⇒ Improves system-
level reliability and does not require V_DSS derating
▪ 500 V / 0.57 Ω, 160 W (120 Vac input)
Continued on the next page…
Package: 6-pin TO-220
Description
The STR-W6735 is a quasi-resonant topology IC designed for
SMPS applications. It shows lower EMI noise characteristics
than conventional PWM solutions, especially at greater than
2 MHz. It also provides a soft-switching operation to turn on the
internal MOSFET at close to zero voltage (V_DS bottom point)
by use of the resonant characteristic of primary inductance
and a resonant capacitor.
The package is a fully molded TO-220, which contains the
controller chip (MIC) and MOSFET, enabling output power up
to 160 W with a 120 Vac input. The bottom-skip function skips
the first bottom of V_DS and turns on the MOSFET at the second
bottom point, to minimize an increase of operational frequency
at light output load, improving system-level efficiency over
the entire load range.
There are two standby functions available to reduce the input
power under very light load conditions. The first is an auto-burst
mode operation that is internally triggered by periodic sensing,
and the other is a manual standby mode, which is executed
by clamping the secondary output. In general applications,
the manual standby mode reduces the input power further
compared to the auto-burst mode.
The soft-start function minimizes surge voltage and reduces
power stress to the MOSFET and to the secondary rectifying
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Typical Application
D
VCC
1
4
STR-W6735
3
S/GND
ROCP
Cont
7
OCP
/BD
6
FB
5
RX
SS
/OLP
CX
P
S1
+B
ErrAmp A
D
S2
B SI
GND
Standby
ON/OFF
LowB
Standby
Out
GND
A For ErrAmp, Sanken SE series device recommended
B For SI, Sanken linear regulator IC recommended
28103.30-5