8.1 Overview

The isolator in Figure 14 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
150 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.

8.2 Functional Block Diagram

Figure 14. Conceptual Block Diagram of a Digital Capacitive Isolator

8.3 Feature Description

8.3.1 Insulation and Safety-Related Specifications

PARAMETER		TEST CONDITIONS		MIN	TYP	MAX	UNIT
VIOTM	Maximum transient overvoltage per DIN V VDE V 0884-10 (VDE V 0884-10):2006-12					4242	VPK
VIORM	Maximum working voltage per DIN V VDE V 0884-10 (VDE V 0884-10):2006-12					566	VPK
VISO	Isolation Voltage per UL 1577	VTEST = VISO, t = 60 sec (qualification)				2500	VRMS
		VTEST = 1.2 * VISO, t = 1 sec (100% production)				3000
VPR	Input-to-output test voltage per DIN V VDE V 0884-10 (VDE V 0884-10):2006-12	After Input/Output safety test subgroup 2/3, VPR = VIORM x 1.2, t = 10 s, Partial discharge < 5 pC				679	VPK
		Method a, After environmental tests subgroup 1, VPR = VIORM x 1.6, t = 10 s, Partial discharge < 5 pC				906
		Method b1, 100% production test, VPR = VIORM x 1.875, t = 1 s, Partial discharge < 5 pC				1061
L(I01)	Minimum air gap (clearance)	Shortest terminal to terminal distance through air		3.7			mm
L(I02)	Minimum external tracking (creepage)	Shortest terminal to terminal distance across the package surface		3.7			mm
	Minimum internal gap (internal clearance)	Distance through the insulation		0.014			mm
	Pollution degree				2
CTI	Tracking resistance (comparative tracking index)	DIN IEC 60112 / VDE 0303 Part 1		≥400			V
RIO(1)	Isolation Resistance, Input to Output	VIO = 500 V, TA = 25oC			>1012		Ω
		VIO = 500 V, 100oC ≤ TA ≤ TA max			>1011
CIO(1)	Barrier capacitance, input to output	VI = 0.4 sin (2πft), f = 1 MHz			2.3		pF
CI(2)	Input capacitance	VI = VCC/2 + 0.4 sin (2πft), f = 1 MHz, VCC = 5 V			2.8		pF

(1) All pins on each side of the barrier tied together creating a two-terminal device.

(2) Measured from input pin to ground.

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 in certain cases. Techniques such as inserting grooves and/or ribs on a PCB are used to help increase these specifications.

Table 2. IEC 60664-1 Ratings Table

PARAMETER	TEST CONDITIONS	SPECIFICATION
Basic Isolation Group	Material Group	II
Installation classification	Rated mains voltage ≤ 150 VRMS	I–IV
	Rated mains voltage ≤ 300 VRMS	I–III
	Rated mains voltage ≤ 400 VRMS	I–II

8.3.1.1 Safety Limiting Values

Safety limiting intends to prevent potential damage to the isolation barrier upon failure of input or output circuitry. A failure of the IO 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	DBQ-16	RθJA = 104.5°C/W, VI = 5.5V, TJ = 150°C, TA = 25°C			217	mA
			RθJA = 104.5°C/W, VI = 3.6V, TJ = 150°C, TA = 25°C			332
			RθJA = 104.5°C/W, VI = 2.7V, TJ = 150°C, TA = 25°C			443
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.

Figure 15. DBQ-16 θ_JC Thermal Derating Curve

8.3.1.2 Regulatory Information

VDE	UL	CSA	CQC
Certified according to DIN V VDE V 0884-10 (VDE V 0884-10):2006-12 and DIN EN 61010-1	Recognized under UL 1577 Component Recognition Program	Approved under CSA Component Acceptance Notice 5A, IEC 60950-1, and IEC 61010-1	Certified according to GB 4943.1-2011
Basic Insulation Maximum Transient Overvoltage, 4242 VPK Maximum Working Voltage, 566 VPK	Single protection, 2500 VRMS(1)	Reinforced Insulation per CSA 60950-1-03 and IEC 60950-1 (2nd Ed.), 185 VRMS maximum working voltage Basic Insulation per CSA 60950-1-03 and IEC 60950-1 (2nd Ed.), 370 VRMS maximum working voltage Reinforced Insulation per CSA 61010-1-12 and IEC 61010-1 (3rd Edition), 150 VRMS maximum working voltage Basic Insulation per CSA 61010-1-12 and IEC 61010-1 (3rd Edition), 300 VRMS maximum working voltage	Basic Insulation, Altitude ≤ 5000m, Tropical Climate, 250 VRMS maximum working voltage
Certificate number: 40016131	File number: E181974	Master contract number: 220991	Certificate number: CQC14001109540

(1) Production tested ≥ 3000 Vrms for 1 second in accordance with UL 1577.

8.4 Device Functional Modes

Figure 16. Device I/O Schematics