Rev. B 03/10

9

TOP264-271

www.powerint.com

Figure 8.

VOLTAGE MONITOR and EXTERNAL CURRENT LIMIT (E and V package) Pin Characteristics.

-250

-200

-150

-100

-50

0

25

50

75

100

125

336

PI-5528-060409

Output

MOSFET

Switching

(Enabled)

(Disabled)

(Non-Latching) (Latching)

Current

Limit

V Pin

X Pin

Maximum

Duty Cycle

I

I

I

I

Pin Voltage

Note: This figure provides idealized functional characteristics with typical performance values. Please refer to the parametric

table and typical performance characteristics sections of the data sheet for measured data. For a detailed description of

each functional pin operation refer to the Functional Description section of the data sheet.

X and V Pins Current (

µA)

Disabled when supply

output goes out of

regulation

section above) and runs entirely off the high voltage DC input,

but with very low power consumption (<100 mW typical at

230 VAC with X pin open). When the TOP264-271 is remotely

turned on after entering this mode, it will initiate a normal

start-up sequence with soft-start the next time the CONTROL

pin reaches 5.8 V. In the worst case, the delay from remote-on

to start-up can be equal to the full discharge/charge cycle time

of the CONTROL pin, which is approximately 125 ms for a

47

mF CONTROL pin capacitor. This reduced consumption

remote off mode can eliminate expensive and unreliable in-line

mechanical switches. It also allows for microprocessor

controlled turn-on and turn-off sequences that may be required

in certain applications such as inkjet and laser printers.

Soft-Start

The 17 ms soft-start sweeps the peak drain current and switching

frequency linearly from minimum to maximum value by operating

through the low frequency PWM mode and the variable

frequency mode before entering the full frequency mode. In

addition to start-up, soft-start is also activated at each restart

attempt during auto-restart and when restarting after being in

hysteretic regulation of CONTROL pin voltage (V

remote OFF or thermal shutdown conditions. This effectively

minimizes current and voltage stresses on the output MOSFET,

the clamp circuit and the output rectifier during start-up. This

feature also helps minimize output overshoot and prevents

saturation of the transformer during start-up.