HCPL-788J Avago Technologies US Inc., HCPL-788J Datasheet - Page 13

• Manufacturer Part Number: HCPL-788J
• Description: OPTOCOUPLR AMP CURR SENSE 16SOIC
• Manufacturer: Avago Technologies US Inc.
• Series: -r
• Type: Current Sensorr

Specifications of HCPL-788J

• Package Type: SOIC
• Operating Supply Voltage (typ): 5V
• Voltage - Isolation: 3750Vrms
• Input Type: DC
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.295", 7.50mm Width)
• No. Of Amplifiers: 1
• Input Offset Voltage: 3mV
• Bandwidth: 30kHz
• Isolation Voltage: 3.75kV
• Supply Voltage Range: ± 4.5V To ± 5.5V
• Supply Current: 20mA
• Amplifier Case Style: SOIC
• No. Of Pins: 16
• Rohs Compliant: No
• Lead Free Status / RoHS Status: Not Compliant

Applications Information
Production Description
Figure 21 shows the internal block diagram of the HCPL-
788J. The analog input (V
using a sigma-delta (∑-Δ) analog to digital (A/D) convert-
er. This A/D samples the input 6 million times per second
and generates a high speed 1-bit output representing
the input very accurately. This 1 bit data stream is trans-
mitted via a light emitting diode (LED) over the optical
barrier after encoding. The detector converts the optical
signal back to a bit stream. This bit stream is decoded
and drives a 1 bit digital to analog (D/A) con verter. Finally
a low pass filter and output buffer drive the output signal
(V
put signal full-scale range is determined by the external
reference voltage (V
(which can be the supply voltage), the full-scale range of
the HCPL-788J can precisely match the full-scale range of
an external A/D converter.
In addition, the HCPL-788J compares the analog input
(V
If the input exceeds the full-scale range, the short-circuit
fault output (FAULT) is activated quickly. This feature op-
erates indepen dently of the ∑-Δ A/D converter in order
to provide the high-speed response (typically 3 μs) need-
Figure 22. ABSVAL with 3 phases, wired-ORed
together.
13
OUT
IN
4.0
3.0
2.0
1.0
) to both the negative and positive full-scale values.
0
) which linearly rep re sents the analog input. The out-
0
0.01
TIME – SECONDS
0.02
REF
). By sharing this reference voltage
IN
) is con verted to a digital signal
0.03
0.04
Figure 23. ABSVAL with 2 phases, wired-ORed
together.
4.0
3.0
2.0
1.0
0
0
0.01
TIME – SECONDS
0.02
ed to protect power tran sistors. The FAULT output is wire
OR-able so that a short circuit on any one motor phase
can be detected using only one signal.
One other output is provided — the rectified output
(ABSVAL). This output is also wire OR-able. The motor
phase having the highest instantaneous rectified out-
put pulls the common output high. When three sinu-
soidal motor phases are combined, the rectified output
(ABSVAL) is essentially a DC signal represent ing the rms
motor current. This single DC signal and a threshold
comparator can indicate motor overload conditions be-
fore dam age to the motor or drive occur. Figure 22 shows
the ABSVAL output when 3 HCPL-788Js are used to mon-
itor a sinusoidal 60 Hz current. Figures 23 and 24 show
the ABSVAL output when only 2 or 1 of the 3 phases are
monitored, respectively.
The HCPL-788J’s other main function is to provide gal-
vanic isolation between the analog input and the ana-
log output. An internal voltage reference determines the
full-scale analog input range of the modulator (approxi-
mately ±256 mV); an input range of ±200 mV is recom-
mended to achieve optimal performance.
0.03
0.04
Figure 24. ABSVAL with 1 phase.
4.0
3.0
2.0
1.0
0
0
0.01
TIME – SECONDS
0.02
0.03
0.04