SLLSE39E June 2010 – May 2015 ISO7520C , ISO7521C
PRODUCTION DATA.
The isolator in Figure 7 is based on a capacitive isolation barrier technique. The I/O channel of the device consists of two internal data channels, a high-frequency channel (HF) with a bandwidth from 100 kbps up to 1 Mbps, and a low-frequency channel (LF) covering the range from 100 kbps down to DC. In principle, a single- ended input signal entering the HF-channel is split into a differential signal through the inverter gate at the input. The following capacitor-resistor networks differentiate the signal into transients, which then are converted into differential pulses by two comparators. The comparator outputs drive a NOR-gate flip-flop whose output feeds an output multiplexer. A decision logic (DCL) at the driving output of the flip-flop measures the durations between signal transients. If the duration between two consecutive transients exceeds a certain time limit, (as in the case of a low-frequency signal), the DCL forces the output-multiplexer to switch from the high- to the low frequency channel. Because low-frequency input signals require the internal capacitors to assume prohibitively large values, these signals are pulse-width modulated (PWM) with the carrier frequency of an internal oscillator, thus creating a sufficiently high frequency signal, capable of passing the capacitive barrier. As the input is modulated, a low-pass filter (LPF) is needed to remove the high-frequency carrier from the actual data before passing it on to the output multiplexer.
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT | |
---|---|---|---|---|---|---|
L(I01) | Minimum air gap (Clearance) | Shortest terminal-to-terminal distance through air | 8.34 | mm | ||
L(I02) | Minimum external tracking (Creepage) | Shortest terminal-to-terminal distance across the package surface | 8.1 | mm | ||
CTI | Tracking resistance (Comparative Tracking Index) | DIN EN 60112 (VDE 0303-11); IEC 60112 | >400 | V | ||
Minimum internal gap (Internal Clearance) | Distance through the insulation | 0.014 | mm | |||
RIO | Isolation resistance, input to output(1) | VIO = 500 V, TA = 25ºC | >1012 | Ω | ||
VIO = 500 V, 100ºC ≤ TA ≤ TA max | >1011 | |||||
CIO | Barrier capacitance input to output(1) | VIO = 0.4 sin(2πft), f = 1 MHz | 2 | pF | ||
CI | Input capacitance to ground(2) | VI = VCC/2 + 0.4 sin(2πft), f = 1 MHz, VCC = 5 V | 2 | pF |
NOTE
Creepage and clearance requirements should be applied according to the specific equipment isolation standards of an application. Care should be taken to maintain the creepage and clearance distance of a board design to ensure that the mounting pads of the isolator on the printed-circuit-board (PCB) do not reduce this distance.
Creepage and clearance on a PCB become equal according to the measurement techniques shown in the Isolation Glossary. Techniques such as inserting grooves and/or ribs on a printed circuit board are used to help increase these specifications.
Safety limiting intends to prevent potential damage to the isolation barrier upon failure of input or output circuitry. A failure of the I/O can allow low resistance to ground or the supply and, without current-limiting, dissipate sufficient power to overheat the die and damage the isolation barrier potentially leading to secondary system failures.
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT | |
---|---|---|---|---|---|---|
Is | Safety input, output, or supply current | θJA =79.9°C/W, VI = 5.25 V, TJ = 150°C, TA = 25°C | 298 | mA | ||
θJA =79.9°C/W, VI = 3.45 V, TJ = 150°C, TA = 25°C | 453 | |||||
Ts | Maximum Case Temperature | 150 | °C |
The safety-limiting constraint is the absolute maximum junction temperature specified in the absolute maximum ratings table. The power dissipation and junction-to-air thermal impedance of the device installed in the application hardware determines the junction temperature. The assumed junction-to-air thermal resistance in the Thermal Information table is that of a device installed on a High-K Test Board for Leaded Surface-Mount Packages. The power is the recommended maximum input voltage times the current. The junction temperature is then the ambient temperature plus the power times the junction-to-air thermal resistance.
VCCI(1) | VCCO(1) | INPUT (INA, INB)(1) | OUTPUT (OUTA, OUTB)(1) |
---|---|---|---|
PU | PU | H | H |
L | L | ||
Open | H | ||
PD | PU | X | H |
X | PD | X | Undetermined |