TNY177PN Просмотр технического описания (PDF) - Power Integrations, Inc

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TNY177PN

TinySwitch-LT Family Energy Efficient, Offline Switcher with Enhanced Flexibility and Extended Power Range®

Power Integrations, Inc 

TNY174-180

VEN

CLOCK

DMAX

IDRAIN

VDRAIN

200

100

V

DC-INPUT

0

10

5

V

BYPASS

0

400

200

V

DRAIN

0

0

1

2

Time (ms)

Figure 10. Power Up.

Figure 9. Operation at Very Light Load.

PI-2661-072400

Figure 11 illustrates a typical power down timing waveform.

No bias winding is needed to provide power to the chip

because it draws the power directly from the DRAIN pin (see

Functional Description above). This has two main benefits.

First, for a nominal application, this eliminates the cost of a

bias winding and associated components. Secondly, for battery

charger applications, the current-voltage characteristic often

allows the output voltage to fall close to zero volts while still

delivering power. TinySwitch-LT accomplishes this without a

forward bias winding and its many associated components. For

applications that require very low no-load power consumption

(50 mW), a resistor from a bias winding to the BYPASS/

MULTI-FUNCTION pin can provide the power to the chip.

The minimum recommended current supplied is 1 mA. The

BYPASS/MULTI-FUNCTION pin in this case will be clamped

at 6.4 V. This method will eliminate the power draw from the

DRAIN pin, thereby reducing the no-load power consumption

and improving full-load efficiency.

Current Limit Operation

Each switching cycle is terminated when the DRAIN current

reaches the current limit of the device. Current limit operation

provides good line ripple rejection and relatively constant power

delivery independent of input voltage.

BYPASS/MULTI-FUNCTION Pin Capacitor

The BYPASS/MULTI-FUNCTION pin can use a ceramic

capacitor as small as 0.1 μF for decoupling the internal power

supply of the device. A larger capacitor size can be used to adjust

the current limit. For TNY175-180, a 1 μF BP/M pin capacitor

will select a lower current limit equal to the standard current

6A

08/07

200

V

100

DC-INPUT

0

400

300

200

V

DRAIN

100

0

0

.5

1

Time (s)

Figure 11. Normal Power Down Timing.

limit of the next smaller device and a 10 μF BP/M pin capacitor

will select a higher current limit equal to the standard current

limit of the next larger device. The higher current limit level of

the TNY180 is set to 850 mA typical. The TNY174 MOSFET

does not have the capability for increased current limit so this

feature is not available in this device.

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