Isolation Amplifier with Short
Circuit and Overload Detection
Technical Data
HCPL-788J
Features
• Output Voltage Directly
Compatible with A/D
Converters (0 V to V
REF
)
• Fast (3
µ
s) Short Circuit
Detection with Transient
Fault Rejection
• Absolute Value Signal Out-
put for Overload Detection
• 1
µ
V/
°
C Offset Change vs.
Temperature
• SO-16 Package
• -40
°
C to +85
°
C Operating
Temperature Range
• 25 kV/
µ
s Isolation Transient
Immunity
• Regulatory Approvals
(Pending): UL, CSA, VDE
0884 (891 Vpeak Working
Voltage)
Low Cost Three Phase Current Sensing with Short Circuit and Overload Detection
ISOLATION BOUNDARY
1
2
3
4
5
6
7
8
+5 V
V
IN+
V
IN-
FAULT
ABSVAL
V
OUT
V
REF
16
15
14
13
12
11
10
R
SENSE1
SHORT CIRCUIT FAULT
MICRO
CONTROLLER
HCPL-788J
9
ISOLATION BOUNDARY
1
2
3
4
5
6
7
A/D
CONVERTER
V
IN+
V
IN-
FAULT
ABSVAL
V
OUT
V
REF
16
15
14
13
12
11
10
R
SENSE2
V
REF
M
3 PHASE
MOTOR
8
HCPL-788J
9
ISOLATION BOUNDARY
1
2
3
4
5
6
7
8
3 PHASE ABSOLUTE
VALUE OUTPUT
V
IN+
V
IN-
FAULT
ABSVAL
V
OUT
V
REF
16
15
14
13
12
11
10
R
SENSE3
+
–
+
–
V
TH
OVERLOAD
FAULT
HCPL-788J
9
Hewlett-Packard’s Isolation Amplifier with Short Circuit and Overload Detection makes
motor phase
current sensing compact, affordable and easy-to-implement
while satisfying worldwide safety and
regulatory requirements.
CAUTION:
It is advised that normal static precautions be taken in handling and assembly of this component to prevent damage and/
or degradation which may be induced by ESD.
2
Description
The HCPL-788J isolation amplifier
is designed for current sensing in
electronic motor drives. In a
typical implementation, motor
currents flow through an external
resistor and the resulting analog
voltage drop is sensed by the
HCPL-788J. A larger analog
output voltage is created on the
other side of the HCPL-788J’s
optical isolation barrier. The
output voltage is proportional
to the motor current and can be
connected directly to a single-
supply A/D converter. A digital
over-range output (FAULT) and
an analog rectified output
(ABSVAL) are also provided. The
wire OR-able over-range output
(FAULT) is useful for quick
detection of short circuit con-
ISOLATION BOUNDARY
HCPL-788J
ditions on any of the motor
phases. The wire-OR-able rectified
output (ABSVAL), simplifies
measurement of motor load since
it performs polyphase rectification.
Since the common-mode voltage
swings several hundred volts in
tens of nanoseconds in modern
electronic motor drives, the
HCPL-788J was designed to
ignore very high common-mode
transient slew rates (10 kV/µs).
µC
INPUT
CURRENT
+
R
SHUNT
0.02
Ω
39
Ω
1
.01 µF
2
3
0.1 µF
4
C
L
V
DD1
V
LED+
V
DD1
GND
1
V
IN-
C
H
V
IN+
GND
2
V
DD2
FAULT
ABSVAL
V
OUT
V
REF
V
DD2
GND
2
16
0.1 µF
15
4.7 kΩ
14
13
12
11
10
9
TO OTHER
PHASE
OUTPUTS
ISOLATED +5 V
5
6
7
0.1 µF
8
A/D
V
REF
GND
+5 V
Figure 1. Current Sensing Circuit.
Pin Descriptions
Symbol
Description
V
IN+
Positive input voltage (± 200 mV
recommended).
V
IN-
Negative input voltage (normally
connected to GND
1
).
Internal Bias Node. Connections to or
between C
H
and C
L
other than the re-
quired 0.1
µF
capacitor shown, are not
recommended.
Supply voltage input (4.5 V to 5.5 V).
Symbol
Description
GND
2
Ground input.
V
DD2
FAULT
Supply voltage input (4.5 V to 5.5 V).
Short circuit fault output. FAULT changes
from a high to low output voltage within
6
µs
after V
IN
exceeds the FAULT Detec-
tion Threshold. FAULT is an open drain
output which allows outputs from all the
HCPL-788Js in a circuit to be connected
together (“wired-OR”) forming a single
fault signal for interfacing directly to the
micro-controller.
C
H
C
L
V
DD1
V
LED+
LED anode. This pin must be left uncon-
nected for guaranteed data sheet perfor-
mance. (For optical coupling testing only.)
Supply voltage input (4.5 V to 5.5 V).
ABSVAL Absolute value of V
OUT
output. ABSVAL
is 0 V when V
IN
=0 and increases toward
V
REF
as V
IN
approaches +256 mV or
-256 mV. ABSVAL is “wired-OR” able
and is used for detecting overloads.
V
OUT
V
REF
Voltage output. Swings from 0 to V
REF
.
The nominal gain is V
REF
/504 mV.
Reference voltage input (4.0 V to V
DD2
).
This voltage establishes the full scale
output ranges and gains of V
OUT
and
ABSVAL.
Supply voltage input (4.5 V to 5.5 V).
Ground input.
V
DD1
GND
1
Ground input.
V
DD2
GND
2
3
Ordering Information
Specify Part Number followed by Option Number (if desired).
Example
HCPL-788J#XXX
No Option = 16-Lead, Surface Mt. package, 45 per tube.
500 = Tape and Reel Packaging Option, 850 per reel.
Option Data sheets available. Contact Hewlett-Packard sales representative, authorized distributor, or visit
our Web site at www.hp.com/go/isolator.
Package Outline Drawings
16-Lead Surface Mount
dimensions in inches
(millimeters)
Note: Initial and continued
variation in the color of the
HCPL-788J’s white mold
compound is normal and does
not affect device performance
or reliability.
0.018
(0.457)
16 15 14 13 12 11 10 9
0.050
(1.270)
TYPE NUMBER
DATE CODE
HP 788J
YYWW
0.295 ± 0.010
(7.493 ± 0.254)
1
2
3
4
5
6
7
8
0.345 ± 0.010
(8.986 ± 0.254)
0.406 ± 0.10
(10.312 ± 0.254)
9°
ALL LEADS
TO BE
COPLANAR
± 0.002
0.018
(0.457)
0.138 ± 0.005
(3.505 ± 0.127)
0–8°
0.025 MIN.
0.408 ± 0.010
(10.160 ± 0.254)
0.008 ± 0.003
(0.203 ± 0.076)
STANDOFF
Package Characteristics
Parameter
Symbol
Input-Output Momentary
V
ISO
Withstand Voltage
Resistance (Input-Output)
R
I-O
Capacitance (Input-Output)
C
I-O
Input IC Junction-to-Case
θjci
Thermal Resistance
Output IC Junction-to-Case
θjco
Thermal Resistance
Min.
3750
Typ.
Max.
Units
Vrms
Ω
pF
°C/W
>10
9
1.3
120
100
Test Conditions
RH < 50%, t = 1
min., T
A
= 25°C
V
I-O
= 500 V
DC
f = 1 MHz
T
A
= 85°C
Fig.
Notes
1,2,3
3
Maximum Solder Reflow Temperature Profile
260
240
220
200
180
160
140
120
100
80
60
40
20
0
0
∆T
= 145°C, 1°C/SEC
∆T
= 115°C, 0.3°C/SEC
TEMPERATURE – °C
∆T
= 100°C, 1.5°C/SEC
1
2
3
4
5
6
7
8
9
10
11
12
TIME – MINUTES
(NOTE: USE OF NON-CHLORINE ACTIVATED FLUXES IS RECOMMENDED.)
4
Regulatory Information
The HCPL-788J is pending approval by the following organizations:
VDE
Approved under VDE0884/06.92
with V
IORM
= 891 Vpeak.
UL
Recognized under UL 1577, com-
ponent recognition program, File
E55361.
CSA
Approved under CSA Component
Acceptance Notice #5, File CA
88324.
VDE 0884 Insulation Characteristics*
Description
Installation classification per DIN VDE 0110/1.89, Table 1
for rated mains voltage
≤
300 V
rms
for rated mains voltage
≤
300 V
rms
for rated mains voltage
≤
600 V
rms
Climatic Classification
Pollution Degree (DIN VDE 0110/1.89)
Maximum Working Insulation Voltage
Input to Output Test Voltage, Method b**
V
IORM
x 1.875 = V
PR
, 100% Production Test with
tm = 1 sec, Partial discharge < 5 pC
Input to Output Test Voltage, Method a**
V
IORM
x 1.5 = V
PR
, Type and Sample Test, t
m
= 60 sec,
Partial discharge < 5 pC
Highest Allowable Overvoltage
(Transient Overvoltage t
ini
= 10 sec)
Safety-limiting values — maximum values allowed in the
event of a failure, also see Figure 2.
Case Temperature
Input Power
Output Power
Insulation Resistance at T
SI
, V
IO
= 500 V
Symbol
Characteristic
I-IV
I-III
I-II
55/85/21
2
891
1670
Unit
V
IORM
V
PR
V
PEAK
V
PEAK
V
PR
V
IOTM
1336
6000
V
PEAK
V
PEAK
T
S
P
S1, INPUT
P
S1, OUTPUT
R
S
175
400
600
>10
9
°C
mW
mW
Ω
* Isolation characteristics are guaranteed only within the safety maximum ratings which must be ensured by protective circuits within
the application. Surface Mount Classification is class A in accordance with CECC00802.
** Refer to the optocoupler section of the isolation and Control Components Designer’s Catalog, under Product Safety Regulations
section, (VDE-0884) for a detailed description of Method a and Method b partial discharge test profiles.
800
P
si
– OUTPUT
P
si
– INPUT
P
s
– POWER – mW
600
400
200
0
0
25
50
75 100 125 150 175 200
T
S
– CASE TEMPERATURE – °C
Figure 2. Dependence of Safety-
Limiting Values on Temperature.
5
Insulation and Safety Related Specifications
Parameter
Minimum External Air Gap
(Clearance)
Minimum External Tracking
(Creepage)
Minimum Internal Plastic Gap
(Internal Clearance)
Tracking Resistance
(Comparative Tracking Index)
Isolation Group
Symbol
L(101)
L(102)
Min.
8.3
8.3
0.5
Max.
mm
mm
mm
Conditions
Measured from input terminals to output
terminals, shortest distance through air.
Measured from input terminals to output
terminals, shortest distance path along body.
Through insulation distance conductor to
conductor, usually the straight line distance
thickness between the emitter and detector.
DIN IEC 112/VDE 0303 Part 1
Material Group (DIN VDE 0110, 1/89, Table 1)
CTI
>175
IIIa
Volts
Absolute Maximum Ratings
Parameter
Storage Temperature
Operating Temperature
Supply Voltages
Steady-State Input Voltage
2 Second Transient Input Voltage
Output Voltage
Absolute Value Output Voltage
Reference Input Voltage
Reference Input Current
Output Current
Absolute Value Current
FAULT Output Current
Input IC Power Dissipation
Output IC Power Dissipation
Solder Reflow Temperature Profile
V
OUT
ABSVAL
V
REF
I
REF
I
VOUT
I
ABSVAL
I
FAULT
P
I
P
O
Symbol
T
S
T
A
V
DD1
, V
DD2
V
IN+
, V
IN-
Min.
-55
-40
0.0
-2.0
-6.0
-0.5
-0.5
0
V
DD2
+ 0.5
V
DD2
+ 0.5
V
DD2
+ 0.5 V
20
20
20
20
200
200
See Package Outline Drawings section
mW
mA
5
Max.
125
100
5.5
V
DD1
+ 0.5
V
4
Units
°C
Note
Recommended Operating Conditions
Parameter
Ambient Operating Temperature
Supply Voltages
Input Voltage (accurate and linear)
Input Voltage (functional)
Reference Input Voltage
FAULT Output Current
Symbol
T
A
V
DD1
, V
DD2
V
IN+
, V
IN-
V
IN+
, V
IN-
V
REF
I
FAULT
Min.
-40
4.5
-200
-2
4.0
Max.
85
5.5
200
2
V
DD2
4
mA
Units
°C
V
mV
V
Note
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