PWS740

PWS740 BURR-BROWN | Alldatasheet

Document overview

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Technical content

Distributed Multi-Channel Isolated DC-TO-DC CONVERTER

FEATURES

l ISOLATED ±7 TO ±20VDC OUTPUTS l BARRIER 100% TESTED AT 1500VAC, 60Hz l LOWEST POSSIBLE COST PER CHANNEL l MINIMUM PC BOARD SPACE l 80% EFFICIENCY (8 CHANNELS, RATED LOADS) l FLEXIBLE USE WITH PWS745 COMPONENTS

APPLICATIONS

l INDUSTRIAL MEASUREMENT AND CONTROL l DATA ACQUISITION SYSTEMS l TEST EQUIPMENT

DESCRIPTION

The PWS740 is a multichannel, isolated DC-to-DC converter with a 1500VAC continuous isolation rat- ing. The outputs track the input voltage to the con- verter over the range of 7 to 20VDC. The converter’s modular design, comprising three components, mini- mizes the cost of isolated multichannel power for the user. The PWS740-1 is a high-frequency (400kHz nominal) oscillator/driver, handling up to eight channels. This part is a hybrid containing an oscillator and two power FETs. It is supplied in a TO-3 case to provide the power dissipation necessary at full load. Transformer impedance limits the maximum input current to about 700mA at 15V input, well within the unit’s thermal limits. A TTL-compatible ENABLE pin provides out- put shut-down if desired. A SYNC pin allows syn- chronization of several PWS740-1s. The PWS740-2 is a trifilar-wound isolation trans- former using a ferrite core and is encapsulated in a plastic package, allowing a higher isolation voltage rating. One PWS740-2 is used per isolated channel. © 1987 Burr-Brown Corporation PDS-758H Printed in U.S.A. January, 1998 International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111 Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 Up to

6 More

20µH Oscillator/ Driver 1 2 654 0.3µF * Optional features; if unused, leave open. ** User Option 0.3µF VDRIVE PWS740-1 10µF PWS740-2 TO OT 654 313 0.3µF BAV99 Functional Diagram BAV99 0.3µF 10µH 10µH +VOGnd1–VO 0.3µF BAV99 BAV99 0.3µF 10µH 10µH +V OGnd1–VO PWS740

At VIN = 15V, output load on each of 8 channels = ±15mA, TA = +25°C, unless otherwise specified. PARAMETER CONDITION MIN TYP MAX UNITS PWS740 SYSTEM ISOLATION Rated Voltage Continuous, AC, 50/60Hz 1500 VACrms Continuous, DC 2121 VDC Test Voltage 10s, minimum 4000 VACrms Impedance Measured from Pin 2 to Pin 5 of the PWS740-2 10 12 || 3 Ω || pF Leakage Current 240VACrms, 60Hz Per Channel 0.5 1.5 µA INPUT Rated Voltage 15 VDC Voltage Range 7 20 VDC Current ±30mA Output Load on 8 Channels, VIN = 15V 520 mA Rated Output Load on 8 Channels, VIN = 15V 300 mA Current Ripple Full Output Load on 8 Channels, V IN = 15V with π Filter on Input 1 mA OUTPUT Rated Voltage ±15mA Output Load on 8 Channels 14 15 16 VDC Voltage at Min Load ±1mA/Channel 30 VDC Voltage Range ±15mA Output Load on Each Channel ±7 ±20 VDC VOUT vs Temp ±15mA Output Load on Each Channel ±0.05 V/ °C Load Regulation ±3mA < Output Load < ±30mA 0.25 V/mA Tracking Regulation V OUT /VIN 1.2 V/V Ripple Voltage See Typical Performance Curves Noise Voltage See Theory of Operation Current | +I OUT | + | –IOUT | Each Channel 60 mA TEMPERATURE Specification –25 +85 °C Operation –25 +85 °C PWS740-1 OSCILLATOR/DRIVER Frequency V IN = 15V 350 400 470 kHz Supply 71 5 2 0 V Enable Drivers On 2 V S V Drivers Off 0 0.8 V PWS740-2 ISOLATION TRANSFORMER Isolation Test Voltage 10s, minimum 4000 VACrms 60s, minimum 1500 VACrms Rated Isolation Voltage Continuous 1500 VACrms Isolation Impedance 10 12 || 3 Ω || pF Isolation Leakage 240VAC 0.5 1.5 µA Primary Inductance 400kHz, Pin 1 to Pin 5 300 µH Winding Ratio Primary/Secondary 68/76 DIODE BRIDGE SPECIFICATIONS Reverse Recovery I F = IR = 50mA 40 ns Reverse Breakdown I R = 100µA5 5 V Reverse Current V R = 40V 1.5 µA Forward Voltage I F = 100mA 1.8 V The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems.

PACKAGE INFORMATION

PRODUCT PACKAGE NUMBER (1) PWS740-1 Driver TO-3 030 PWS740-2 Transformer 6-Pin Plastic DIP 216 NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. PWS740-1 Enable +V IN Freq Adj Sync Gnd T O Return T AC Gnd AC T V T 3 4 6 O D O O Plastic DIP PWS740-2 TO-3 (Drawings Not to Scale) ELECTROSTATIC DISCHARGE SENSITIVITY This integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.

TYPICAL PERFORMANCE CURVES V vs C C (µF) V (mVp-p) LOAD RIPPLE RIPPLE LOAD VIN = 15V IO = ±15mA/Channel

1 THROUGH 8 CHANNELS

V (V) 0 5 10 15 20 25 ±V (V) LINE REGULATION 1 channel ±I = ±15mA/ChannelO IN OUT 4 or 8 channels EFFICIENCY vs LOAD 1,4, AND 8 CHANNELS ±I (mA) 100 Efficiency (%) OUT 5 1 01 52 02 53 0 IN

4 Channels

V = +15V

8 Channels

1 Channel

Temperature (°C) –25 –10 Rated V (%) +50 +85 OUT 0 +25 LOAD REGULATION 1, 4 AND 8 CHANNELS ±I (mA) OUT 5 1 01 52 02 53 0 OUT IN 4 and 8 Channel V = 15V FREQUENCY ADJUSTMENT RANGE Frequency Adjustment Resistor ( )Ω 1 10 100 1k 10k 100k 500 400 300 200 100 PWS740-1 Operating Frequency (kHz) See Functional Diagram

provides a bypass for the AC portion of this current. down of the V+ supply is not considered instantaneous. rent flow. Such a voltage spike may damage the PWS740-1. the +VIN pin between –0.6V and +23V, is recommended. tied to a voltage between +2V and +V. slightly higher than that of the highest unsynchronized unit. supply potentials; otherwise, damage may result. slave unit must be grounded to assure synchronization. TransZorb® General Semiconductor Industries Inc. FIGURE 1. Master/Slave Synchronization of Multiple

1 Oscillator/Driver

8 Transformers

8 Bridges

8 ISO102s

1 Multiplexer

Not all components are shown. NOTES: (1) Supplies ±15mA of isolated supply current per channel. (2) WestCap DKM-10 or equivalent. (3) Or ISO120 or ISO122. FIGURE 3. Low Cost Eight-Channel Isolation Amplifier Block with Channel-to-Channel Isolation. netic radiation from the switching signal’s lines. TO and TO . least inductance (and least radiation). pickup of switch signal by the ISO102.

digital ground and the PWS740 ground together locally, leaving the ISO102 analog ground to be connected off of the board; the differential voltage between analog and digital ground may become too great. OUTPUT CURRENT RATINGS The PWS740-1 driver contains “soft-start” driver circuitry to protect the driver FETs and eliminate high inrush currents during turn-on. Because the PWS740 can have between one and eight channels connected, it was not possible to provide a suitable internal current limit within the driver. Instead, impedance-limiting protects the driver and transformer from overload. This means that the internal impedance of each PWS740-2 transformer is high enough that, when short- circuited at its output, it limits the current drawn from the driver to a safe value. In addition, the wire size and mass of the transformer are large enough that the transformer does not receive damage under continuous short-circuit condi- tions. The PWS740-1 is capable of driving up to eight individual channels to their full current rating. The total current which can be drawn from each isolation channel is a function of total power being drawn from both DC V+ and V– outputs. For example, if one output is not used, then maximum current can be drawn from the other output. In all cases, the maximum total current that can be drawn from any indi- vidual channel is: | I It should be noted that many analog circuit functions do not simultaneously draw full rated current from both the positive and negative supplies. Thus, the PWS740 can power more circuits per channel than is first apparent. For example, an operational amplifier does not draw maximum current from both supplies simultaneously. If a circuit draws 10mA from the positive supply and 3mA from the negative supply, the PWS740 could power (60 ÷ 13), about four devices per channel. ISOLATION VOLTAGE RATINGS Because a long-term test is impractical in a manufacturing situation, the generally accepted practice is to perform a production test at a higher voltage for some shorter period of time. The relationship between actual test conditions and the continuous derated maximum specification is an important one. Burr-Brown has chosen a deliberately conservative one: V TEST = (2 x V CONTINUOUS RATING ) + 1000V. This choice is appropriate for conditions where system transient voltages are not well defined. (3) Where the real voltages are well-defined or where the isolation voltage is not continu- ous, the user may choose a less conservative derating to establish a specification from the test voltage. (3) Reference National Electrical Manufacturers Association (NEMA) Standards part ICS I-109 and ICS1-111.