DPA424PN-TL データシートの表示（PDF） - Power Integrations, Inc

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DPA424PN-TL

Highly Integrated DC-DC Converter ICs for Power over Ethernet & Telecom Applications

Power Integrations, Inc 

DPA422-426

LINE-SENSE (L) Pin Operation

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 +240 µA (typical). At +240 µA, this pin turns into a constant

current sink. Refer to Figure 8. 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 five functions available through the use of

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

reduction, remote ON/OFF and synchronization. Shorting the

LINE-SENSE pin to the SOURCE pin disables all five functions.

The LINE-SENSE pin is typically used for line sensing by

connecting a resistor from this pin to the positive input DC

voltage bus to implement OV, UV and line feed-forward with

DCMAX reduction over line voltage. In this mode, the value of the

resistor determines the line OV/UV thresholds, and the DCMAX is

reduced linearly with input DC high-voltage starting from just

above the UV threshold. This pin can also be used as the input

pin for remote ON/OFF and synchronization. An external

transistor placed between the LINE-SENSE pin and the

CONTROL pin realizes remote ON/OFF via UV or OV threshold.

Synchronization is available by connecting an open drain

external MOSFET between the LINE-SENSE pin and the

SOURCE pin to generate synchronization pulse. Each time the

MOSFET turns on, the falling edge of the LINE-SENSE pin

voltage initiates a new switching cycle. The lowest

synchronization frequency guaranteed by DPA-Switch is

128 kHz. Refer to Table 2 for possible combinations of the

functions with example circuits shown in Figure 11 through

Figure 24. A description of specific functions in terms of the

LINE-SENSE pin I/V characteristic is shown in Figure 7 (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 4 µA hysteresis) and OV triggers at IOV (+135 µA typical with

4 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 75% at IL(DC) (+55 µA typical) to 33% at IOV (+135 µA).

EXTERNAL CURRENT LIMIT (X) Pin Operation

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 -230 µA (typical). At -230 µA, it turns into a

constant current source (refer to Figure 8).

There are two functions available through the use of the

EXTERNAL CURRENT LIMIT pin: external current limit and

remote ON/OFF. Shorting the EXTERNAL CURRENT LIMIT pin

and SOURCE pin disables both 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 control input.

Table 2 shows several different ways of using this pin. See

Figure 7 for a description of the functions where the horizontal

axis (left hand side) represents the EXTERNAL CURRENT LIMIT

pin current. The meaning of the vertical axes varies with

function. For those that control the on/off states of the output

such as remote ON/OFF, the vertical axis represents the enable/

disable states of the output. For external current limit, the

vertical axis represents the magnitude of the ILIMIT. Please see

graphs in the Typical Performance Characteristics section for

the current limit programming range and the selection of the

appropriate resistor value.

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Rev. T 12/12

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