Broadcom

- 9 -

HCPL-5300, HCPL-5301, HCPL-530K, 5962-96852

Data Sheet

series resistor. As long as the voltage developed across the

mode failure occurs. Even if the LED momentarily turns on, the

100 pF capacitor from pins 6-5 will keep the output from

dipping below the threshold. The recommended LED drive

circuit (Figure 13) provides about 10V of margin between the

lowest optocoupler output voltage and a 3V IPM threshold

margin can be obtained by adding a diode in parallel with the

resistor, as shown by the dashed line connection in Figure 18,

Since the open collector drive circuit, shown in Figure 19,

performance. Figure 20 is the AC equivalent circuit for

Figure 16 during common mode transients. Essentially all the

the input threshold. Figure 21 is an alternative drive circuit

which does achieve ultra high CMR performance by shunting

the LED in the off state.

IPM Dead Time and Propagation Delay

Specifications

These devices include a Propagation Delay Difference

specification intended to help designers minimize dead time in

their power inverter designs. Dead time is the time period

during which both the high and low side power transistors (Q1

and Q2 in Figure 22) are off. Any overlap in Q1 and Q2

conduction results in large currents flowing through the power

devices between the high and low voltage motor rails.

To minimize dead time, the designer must consider the

propagation delay characteristics of the optocoupler as well as

the characteristics of the IPM IGBT gate drive circuit.

Considering only the delay characteristics of the optocoupler

(the characteristics of the IPM IGBT gate drive circuit can be

analyzed in the same way), it is important to know the

propagation delay specifications, preferably over the desired

operating temperature range.

The limiting case of zero dead time occurs when the input to

Q1 turns off at the same time that the input to Q2 turns on. This

case determines the minimum delay between LED1 turn-off

and LED2 turn-on, which is related to the worst-case

optocoupler propagation delay waveforms, as shown in

Figure 23. A minimum dead time of zero is achieved in

Figure 23 when the signal to turn on LED2 is delayed by

maximum value for the propagation delay difference

specification which is specified at 500 ns for the HCPL-530x

over an operating temperature range of –55°C to +125°C.

Delaying the LED signal by the maximum propagation delay

difference ensures that the minimum dead time is zero, but it

does not tell a designer what the maximum dead time will be.

The maximum dead time occurs in the highly unlikely case

dead time in this case becomes the sum of the spread in the

maximum dead time is also equivalent to the difference

between the maximum and minimum propagation delay

difference specifications. The maximum dead time (due to the

optocouplers) for the HCPL-530x is 670 ns (= 500 ns – (–170 ns))

over an operating temperature range of –55°C to +125°C.