Application information

HVLED002

14/19

DocID028720 Rev 1

5.5

Error amplifier

An error amplifier (E/A) structure is present in the HVLED002 (Figure 15 on page 10). The

non-inverting input is internally connected to a very precise reference voltage (2.5 V ± 2%).

The E/A output and inverting pin are connected respectively to the pin 1 and 2, available for

external compensation. The E/A output will source at least 0.5 mA and sink 2 mA. Figure 8

on page 9 shows the open loop frequency response of the E/A.

The output of the error amplifier can be forced to ground in different ways to shut down the

application as shown in Figure 22.

Figure 22. Shutdown circuitries

5.6

Totem pole output

The HVLED002 has a single totem pole output which can be operated to the ± 1 Amp peak

current for driving MOSFET gates, and a + 200 mA average current for bipolar power

transistors.

Cross conduction between the driver's output transistors is minimal, the average added

power with VIN = 30 V is around 80 mW at 200 kHz.

Limiting the peak current through the IC is accomplished by placing a resistor between the

totem pole output and the gate of the MOSFET. Without this resistor, the peak current is

limited only by the dV/dT rate of the totem pole switching and the FET gate capacitance.

An additional discharging diode can be put in parallel with the said limiting resistor to quickly

turn off the MOSFET, reducing the switching losses and the control to output delay.

BIAS

+

-

EA

R

+

OSC

2N

3905

2N

3903

1 mA

R

R

2R

1

2

8

4

5

AM039818

The simple two-transistor circuit can be used in place of the SCR as shown. All resistors are 10 K .