TOP242-249 データシートの表示（PDF） - Power Integrations, Inc

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TOP242-249

TOPSwitch®-GX Family Extended Power, Design Flexible, EcoSmart®, Integrated Off-line Switcher

Power Integrations, Inc 

Using Feature Pins

FREQUENCY (F) Pin Operation

The FREQUENCY pin is a digital input pin available in the

Y or R package only. Shorting the FREQUENCY pin to

SOURCE pin selects the nominal switching frequency of

132 kHz (Figure 13) which is suited for most applications. For

other cases that may benefit from lower switching frequency

such as noise sensitive video applications, a 66 kHz switching

frequency (half frequency) can be selected by shorting the

FREQUENCY pin to the CONTROL pin (Figure 14). In

addition, an example circuit shown in Figure 15 may be used to

lower the switching frequency from 132 kHz in normal

operation to 66 kHz in standby mode for very low standby

power consumption.

LINE-SENSE (L) Pin Operation (Y and R Packages)

When current is fed into the LINE-SENSE pin, it works as a

voltage source of approximately 2.6 V up to a maximum

current of +400 µA (typical). At +400 µA, this pin turns into

a constant current sink. Refer to Figure 12a. In addition, a

comparator with a threshold of 1 V is connected at the pin and

is used to detect when the pin is shorted to the SOURCE pin.

There are a total of four functions available through the use of

the LINE-SENSE pin: OV, UV, line feed forward with DCMAX

reduction, and remote ON/OFF. Connecting the LINE-SENSE

pin to the SOURCE pin disables all four functions. The LINE-

SENSE pin is typically used for line sensing by connecting a

resistor from this pin to the rectified DC high voltage bus to

implement OV, UV and DCMAX reduction with line voltage. In

this mode, the value of the resistor determines the line OV/UV

thresholds, and the DC is reduced linearly with rectified DC

MAX

high voltage starting from just above the UV threshold. The pin

can also be used as a remote on/off and a synchronization input.

TOP242-249

Refer to Table 2 for possible combinations of the functions with

example circuits shown in Figure 16 through Figure 40. A

description of specific functions in terms of the LINE-SENSE

pin I/V characteristic is shown in Figure 11 (right hand side).

The horizontal axis represents LINE-SENSE pin current with

positive polarity indicating currents flowing into the pin. The

meaning of the vertical axes varies with functions. For those

that control the on/off states of the output such as UV, OV and

remote ON/OFF, the vertical axis represents the enable/disable

states of the output. UV triggers at IUV (+50 µA typical with

30 µA hysteresis) and OV triggers at I (+225 µA typical with

OV

8 µA hysteresis). Between the UV and OV thresholds, the

output is enabled. For line feed forward with DCMAX reduction,

the vertical axis represents the magnitude of the DCMAX. Line

feed forward with DCMAX reduction lowers maximum duty cycle

from 78% at I (+60 µA typical) to 38% at I (+225 µA).

L(DC)

OV

EXTERNAL CURRENT LIMIT (X) Pin Operation

(Y and R Packages)

When current is drawn out of the EXTERNAL CURRENT

LIMIT pin, it works as a voltage source of approximately 1.3

V up to a maximum current of –240 µA (typical). At –240 µA,

it turns into a constant current source (refer to Figure 12a).

There are two functions available through the use of the

EXTERNAL CURRENT LIMIT pin: external current limit

and remote ON/OFF. Connecting the EXTERNAL CURRENT

LIMIT pin and SOURCE pin disables the two functions. In

high efficiency applications this pin can be used to reduce the

current limit externally to a value close to the operating peak

current, by connecting the pin to the SOURCE pin through a

resistor. The pin can also be used as a remote on/off. Table 2

shows several possible combinations using this pin. See Figure

LINE-SENSE AND EXTERNAL CURRENT LIMIT PIN TABLE*

Figure Number

16 17 18 19 20 21 22 23 24 25 26 27 28 29

Three Terminal Operation

✔

Under-Voltage

✔✔

✔✔✔

Overvoltage

✔

✔

✔✔✔

Line Feed Forward (DC )

MAX

✔

Overload Power Limiting

✔

✔✔✔

External Current Limit

✔✔

✔✔

✔✔

Remote ON/OFF

✔✔ ✔ ✔ ✔ ✔

✔

*This table is only a partial list of many LINE-SENSE and EXTERNAL CURRENT LIMIT pin configurations that are possible.

Table 2. Typical LINE-SENSE and EXTERNAL CURRENT LIMIT Pin Configurations.

August 8, 2000

11 E

7/01

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