The ISO122 is a precision isolation amplifier incorporating a novel duty cycle modulation-demodulation technique. The signal is transmitted digitally across a 2-pF differential capacitive barrier. With digital modulation the barrier characteristics do not affect signal integrity, thus resulting in excellent reliability and good high-frequency transient immunity across the barrier. Both barrier capacitors are imbedded in the plastic body of the package.
The ISO122 is easy to use. No external components are required for operation. The key specifications are 0.020% maximum nonlinearity, 50-kHz signal bandwidth, and 200-V/°C VOS drift. A power supply range of 4.5 V to 18 V and quiescent currents of 5 mA on VS1 and ±5.5 mA on VS2 make the ISO122 ideal for a wide range of applications.
The ISO122 is available in 16-pin plastic DIP and
28-lead plastic surface-mount packages.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
ISO122 | PDIP (16) | 17.90 mm × 7.50 mm |
SOIC (28) | 20.01 mm × 6.61 mm |
Changes from * Revision (November1993) to A Revision
PIN | I/O | DESCRIPTION | ||
---|---|---|---|---|
NAME | PDIP | SOIC | ||
GND | 8 | 14 | - | Low-side ground reference |
GND | 16 | 28 | - | High-side ground reference |
VIN | 15 | 27 | I | High-side analog input |
VOUT | 7 | 13 | O | Low-side analog output |
+VS1 | 1 | 1 | - | High-side positive analog supply |
-VS1 | 2 | 2 | - | High-side negative analog supply |
+VS2 | 9 | 15 | - | Low-side positive analog supply |
-VS2 | 10 | 16 | - | Low-side negative analog supply |
MIN | MAX | UNIT | |
---|---|---|---|
Supply voltage | ±18 | V | |
VIN | 100 | V | |
Continuous isolation voltage | 1500 | Vrms | |
Junction temperature | 150 | °C | |
Output short to common | Continuous | ||
Storage temperature, Tstg | –40 | 125 | °C |
VALUE | UNIT | |||
---|---|---|---|---|
V(ESD) | Electrostatic discharge | Human body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) | ±1000 | V |
Charged-device model (CDM), per JEDEC specification JESD22-C101(2) | ±500 |
MIN | NOM | MAX | UNIT | ||
---|---|---|---|---|---|
TA | –25 | 85 | °C | ||
+VS1 | 15 | ||||
-VS1 | –15 | ||||
+VS2 | 15 | ||||
-VS2 | –15 | ||||
VIN | ±10 |
THERMAL METRIC(1) | ISO122 | UNIT | ||
---|---|---|---|---|
NVF (PDIP) | DVA (SOIC) | |||
16 PINS | 28 PINS | |||
RθJA | Junction-to-ambient thermal resistance | 51.0 | 79.8 | °C/W |
RθJC(top) | Junction-to-case (top) thermal resistance | 32.4 | 32.9 | |
RθJB | Junction-to-board thermal resistance | 29.5 | 42.2 | |
ψJT | Junction-to-top characterization parameter | 10.4 | 6.6 | |
ψJB | Junction-to-board characterization parameter | 29.0 | 40.9 |
PARAMETER | TEST CONDITIONS | ISO122P/U | ISO122JP/JU | UNIT | |||||
---|---|---|---|---|---|---|---|---|---|
MIN | TYP | MAX | MIN | TYP | MAX | ||||
ISOLATION | |||||||||
Voltage rated continuous ac 60Hz | 1500 | 1500 | Vac | ||||||
100% Test(1) | 1s, 5pc PD | 2400 | 2400 | Vac | |||||
Isolation Mode Rejection | 60Hz | 140 | 140 | dB | |||||
Barrier Impedance | 1014 || 2 | 1014 || 2 | Ω || pF | ||||||
Leakage Current at 60Hz | VISO = 240Vrms | 0.18 | 0.5 | 0.18 | 0.5 | µArms | |||
GAIN | |||||||||
Nominal Gain | VO = ±10V | 1 | 1 | V/V | |||||
Gain Error | ±0.05 | ±0.50 | ±0.05 | ±0.50 | %FSR | ||||
Gain vs Temperature | ±10 | ±10 | ppm/°C | ||||||
Nonlinearity(2) | ±0.016 | ±0.020 | ±0.025 | ±0.050 | %FSR | ||||
INPUT OFFSET VOLTAGE | |||||||||
Initial Offset | ±20 | ±50 | ±20 | ±50 | mV | ||||
vs Temperature | ±200 | ±200 | µV/°C | ||||||
vs Supply | ±2 | ±2 | mV/V | ||||||
Noise | 4 | µV/√Hz | |||||||
INPUT | |||||||||
Voltage Range | ±10 | ±12.5 | ±10 | ±12.5 | V | ||||
Resistance | 200 | 200 | kΩ | ||||||
OUTPUT | |||||||||
Voltage Range | ±10 | ±12.5 | ±10 | ±12.5 | V | ||||
Current Drive | ±5 | ±15 | ±5 | ±15 | mA | ||||
Capacitive Load Drive | 0.1 | 0.1 | µF | ||||||
Ripple Voltage(3) | 20 | 20 | mVp-p | ||||||
FREQUENCY RESPONSE | |||||||||
Small-Signal Bandwidth | 50 | 50 | kHz | ||||||
Slew Rate | 2 | 2 | V/µs | ||||||
Settling Time 0.10% | VO = ±10V | 50 | 50 | µs | |||||
Settling Time 0.01% | 350 | 350 | µs | ||||||
Overload Recovery Time | 150 | 150 | µs | ||||||
POWER SUPPLIES | |||||||||
Rated Voltage | ±15 | ±15 | V | ||||||
Voltage Range | ±4.5 | ±18 | ±4.5 | ±18 | V | ||||
VS1 | Quiescent Current | ±5 | ±7 | ±5 | ±7 | mA | |||
VS2 | ±5.5 | ±7 | ±5.5 | ±7 | |||||
TEMPERATURE RANGE | |||||||||
Specification | –25 | 85 | –25 | 85 | °C | ||||
Operating | –25 | 85 | –25 | 85 | °C | ||||
Storage | –40 | 125 | –40 | 125 | °C | ||||
θJA | Thermal Resistance | 100 | 100 | °C/W | |||||
θJC | 65 | 65 | °C/W |
f = 2kHz | ||
NOTE: Shaded area shows aliasing frequencies that cannot be removed by a low-pass filter at the output. | ||||
f = 20kHz | ||
The ISO122 isolation amplifier uses an input and an output section galvanically isolated by matched 1-pF isolating capacitors built into the plastic package. The input is duty-cycle modulated and transmitted digitally across the barrier. The output section receives the modulated signal, converts it back to an analog voltage and removes the ripple component inherent in the demodulation. Input and output sections are fabricated, then laser trimmed for exceptional circuitry matching common to the input and output sections. The sections are then mounted on opposite ends of the package with the isolating capacitors mounted between the two sections. The ISO122 contains 250 transistors.
An input amplifier (A1, Functional Block Diagram) integrates the difference between the input current (VIN/200 kΩ) and a switched ±100-mA current source. This current source is implemented by a switchable 200-mA source and a fixed 100-µA current sink. To understand the basic operation of the modulator, assume that VIN = 0 V. The integrator will ramp in one direction until the comparator threshold is exceeded. The comparator and sense amp will force the current source to switch; the resultant signal is a triangular waveform with a 50% duty cycle. The internal oscillator forces the current source to switch at 500 kHz. The resultant capacitor drive is a complementary duty-cycle modulation square wave.
The sense amplifier detects the signal transitions across the capacitive barrier and drives a switched current source into integrator A2. The output stage balances the duty-cycle modulated current against the feedback current through the 200 kW feedback resistor, resulting in an average value at the VOUT pin equal to VIN. The sample and hold amplifiers in the output feedback loop serve to remove undesired ripple voltages inherent in the demodulation process.
The ISO122 is a precision analog isolation amplifier. The input signal is transmitted digitally across a high-voltage differential capacitive barrier. With digital modulation the barrier characteristics do affect signal integrity, resulting in excellent reliability and high-frequency transient immunity.
The ISO122 does not have any additional functional modes.