VB125ASPTR-E

Electrical specifications

Doc ID 018829 Rev 1

9/17

Figure 3.

Temperature compensated high voltage clamp

Tj

Thermal output current control IN = ON (9)

150

°C

td(on)

Turn-on delay time of output

current

See (10)

1µs

td(off)

Turn-off delay time of output

current

See (11)

760

µs

1.

In the high voltage clamping structure of this device a temperature compensation has been implemented.

The circuit schematic is shown in Figure 3. The KVbe cell takes care of the temperature compensation.

The whole electrical characteristic of the new circuit is shown in Figure 4. Up to VCE =nVZ no current flows

into the collector (just the leakage current of the power stage); for nVZ < VCE < Vcl a current begins to flow

across the resistances of the KVbe compensation circuit (typical slope

≅ 20 KΩ) as soon as the Vcl reached

the dinamic resistance drop to ~4

Ω to protect the device against overvoltage (See Figure 5).

2.

The saturation voltage of the Power stage includes the drop on the sensing resistor.

3.

Considering the different ways of operation of the device (with or without spark, etc...) there are some short

periods of time in which the output terminal (HVC) is pulled below ground by a negative current due to

leakage inductances and stray capacitances of the ignition coil. With VIPower devices, if no corrective

action is taken, these negative currents can cause parasitic glitches on the diagnostic output. To kill this

potential problem, a circuit that avoids the possibility for the HVC to be pulled underground, by sending the

required negative current from the battery is implemented in the VB125ASPTR-E. For this reason there are

some short periods in which a current exceeding 220 mA flows in the VCC pin.

4.

A zener protection of 16 V (typical) is placed on the supply pin (VCC) of the chip to protect the internal

circuitry. For this reason, when the battery voltage exceeds that value, the current flowing into VCC pin can

be greater than the maximum current specified at VCC = 14 V (both in power on and power off conditions):

it will be limited by an internal resistor.

5.

The primary coil current value Icl must be measured 1 ms after desaturation of the power stage.

6.

These limits apply with regard to the minimum battery voltage and resistive drop on the coil and cables that

permit to reach the limitation or diagnostic level.

7.

No internal pull-down.

8.

When IC gets over IC(diag), the diagnostic output voltage rises to the high level and so it remains until the

end of the input signal.

9.

Tjmin = 150 °C means that the behavior of the device will not be affected for junction temperature lower

than 150 °C. For higher temperature, the thermal protection circuit begins its action reducing the Icl limit

according with the power dissipation. Chip temperature is a function of the Rth of the whole system in which

the device will be operating (See Figure 6).

10. Turn on delay time measured from 90% of input voltage rising edge to 10% of output voltage falling edge.

11. Turn off delay time is defined as the time between the 90% of input pulse falling edge and the point where

the HVC reaches 200 V.

Table 5.

Electrical characteristics (continued)

Symbol

Parameter

Test conditions

Min

Typ Max Unit

Obsolete

Product(s)

- Obsolete

Product(s)