TEA1708T

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Product data sheet

Rev. 1 — 25 September 2013

3 of 11

NXP Semiconductors

TEA1708T

GreenChip X capacitor discharge IC

7.

Functional description

The TEA1708 incorporates a timer and a zero-crossing mains voltage detector. If a

positive or negative voltage above the threshold zero-crossing mains voltage (20 V) is

applied between the high-voltage pins, the timer charges the external capacitor on the

TMR1 and TMR2 pins. If the voltage between the TMR1 and TMR2 pins reaches 1.2 V, a

discharge current is activated. If the voltage applied between the high-voltage pins, is

below the threshold zero-crossing mains voltage, the external capacitor is discharged and

the discharging stops. The discharge current is internally limited.

When an AC mains voltage is applied, the timer capacitor is charged between the mains

zero crossings and discharged during the mains zero crossings. When the AC mains is

disconnected and a high voltage remains on the X capacitor, the timer charges the

external capacitor above its discharge activation threshold voltage point (1.2 V), switching

on the internally limited discharge current of the external X capacitor.

To protect the IC during mains surges, a high voltage clamping circuit is integrated. The

clamping circuit is activated for > 500 V positive and negative voltages. The high-voltage

pins HV1 and HV2 are fully symmetrical.

Fig 3.

Functional behavior