TOP261EN datasheet(11/48 Pages) POWERINT

11 / 48 page

Rev. F 01/09

TOP252-262

www.powerint.com

Line Overvoltage Shutdown (OV)

The same resistor used for UV also sets an overvoltage

threshold, which, once exceeded, will force TOPSwitch-HX to

stop switching instantaneously (after completion of the current

switching cycle). If this condition lasts for at least 100

μs, the

TOPSwitch-HX output will be forced into off state. Unlike with

TOPSwitch-GX, however, when the line voltage is back to

normal with a small amount of hysteresis provided on the OV

threshold to prevent noise triggering, the state machine sets to

S13 and forces TOPSwitch-HX to go through the entire auto-

restart sequence before attempting to switch again. The ratio

of OV and UV thresholds is preset at 4.5, as can be seen in

Figure 12. When the MOSFET is off, the rectiﬁed DC high

voltage surge capability is increased to the voltage rating of the

MOSFET (700 V), due to the absence of the reﬂected voltage

and leakage spikes on the drain. The OV feature can be

disabled independent of the UV feature.

In order to reduce the no-load input power of TOPSwitch-HX

designs, the V-pin (or M-pin for P Package) operates at very low

currents. This requires careful layout considerations when

designing the PCB to avoid noise coupling. Traces and

components connected to the V-pin should not be adjacent to

any traces carrying switching currents. These include the drain,

clamp network, bias winding return or power traces from other

converters. If the line sensing features are used, then the sense

resistors must be placed within 10 mm of the V-pin to minimize

the V-pin node area. The DC bus should then be routed to the

line sense resistors. Note that external capacitance must not

be connected to the V-pin as this may cause misoperaton of the

V pin related functions.

Hysteretic or Latching Output Overvoltage Protection (OVP)

The detection of the hysteretic or latching output overvoltage

protection (OVP) is through the trigger of the line overvoltage

threshold. The V-pin or M-pin voltage will drop by 0.5 V, and

the controller measures the external attached impedance

immediately after this voltage drops. If I

V or IM exceeds IOV(LS)

(336

μA typical) longer than 100 μs, TOPSwitch-HX will latch

into a permanent off state for the latching OVP. It only can be

reset if V

V or VM goes below 1 V or VC goes below the power-

up-reset threshold (V

C(RESET)) and then back to normal.

If I

V or IM does not exceed IOV(LS) or exceeds no longer than

100

μs, TOPSwitch-HX will initiate the line overvoltage and the

hysteretic OVP. Their behavior will be identical to the line

overvoltage shutdown (OV) that has been described in detail in

the previous section.

Voltage Monitor and External Current Limit Pin Table*

Figure Number

Three Terminal Operation

✓

Line Undervoltage

✓✓✓✓

✓✓

Line Overvoltage

✓✓✓

✓

Line Feed-Forward (DC

MAX)

✓✓✓

✓✓

Output Overvoltage Protection

✓✓

Overload Power Limiting

✓

External Current Limit

✓✓

✓✓✓

Remote ON/OFF

✓✓✓

Device Reset

✓

*This table is only a partial list of many VOLTAGE MONITOR and EXTERNAL CURRENT LIMIT Pin Conﬁgurations that are possible.

Table 2.

VOLTAGE MONITOR (V) Pin and EXTERNAL CURRENT LIMIT (X) Pin Conﬁguration Options.

Multi-Function Pin Table*

Figure Number

Three Terminal Operation

✓

Line Undervoltage

✓✓✓✓

Line Overvoltage

✓✓✓

✓

Line Feed-Forward (DC

MAX)

✓✓✓

Output Overvoltage Protection

✓✓

Overload Power Limiting

✓

External Current Limit

✓✓

Remote ON/OFF

✓✓✓

Device Reset

✓

*This table is only a partial list of many MULTI-FUNCTIONAL Pin Conﬁgurations that are possible.

Table 3.

MULTI-FUNCTION (M) Pin Conﬁguration Options.

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