PWS750

PWS750 BURR-BROWN | Alldatasheet

Document overview

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Technical content

0.3µF 0.3µF 10Ω –VO +VO S D G S D G 2N7002 or 2N7008 2N7002 or 2N7008 0.3µF Driver Soft Start Oscillator R T T 0.3µF Comparator Differential Amplifier +VIN 7 10µH PWS750-1U TTLOUT TTLIN Enable VD Input Gnd (2) (2) (1) 10Ω (1) 10Ω (3) 10Ω (3) Reference S (1) Output Ground The PWS750-2U and PWS750-4U are split-bobbin wound isolation transformers using a ferrite core. They are encapsulated in plastic packages, allowing a high isolation voltage rating. The PWS750-3U is a high-speed monolithic diode bridge in a plastic 8-pin SO package. One PWS750-1U can be used to drive up to four channels (15V nominal operation). One PWS750-2U and PWS750-3U and two 2N7002 (surface mount) or 2N7008 (TO-92) MOSFETs made by Siliconix are used per isolated channel. When a PWS750-4U is used as the transformer (5V input), then two TN0604s made by Supertex must be used, due to the higher currents of the primary (lower RDS on) and the lower VGS threshold. With 5V operation only one channel can be directly driven by the PWS750-1U (a simple FET booster circuit can be used for multichannel operation; see Figure 3). Isolated, Unregulated DC/DC CONVERTER COMPONENTS PWS750

DESCRIPTION

The PWS750 consists of three building blocks for building a low cost DC/DC converter. With them you can optimize DC/DC converter PC board layout or build a multichannel isolated DC/DC converter. All parts are surface mount, requiring minimal space to build the converter. The modular design minimizes the cost of isolated power. The PWS750-1U is a high-frequency (800kHz nomi- nal) driver that can drive N-channel MOSFETs up to the size of a 1.3A 2N7010. The recommended MOSFET for individual transformer drivers is the 2N7008. The PWS750-1U is supplied in a 16-pin double-wide SO package.

APPLICATIONS

G INDUSTRIAL PROCESS CONTROL EQUIPMENT G GROUND-LOOP ELIMINATION G PC-BASED DATA ACQUISITION G VENDING MACHINES

FEATURES

G 100% TESTED FOR HIGH-VOLTAGE BREAKDOWN G COMPACT-SURFACE MOUNT G MULTICHANNEL OPERATION G 5V OR 15V INPUT OPTIONS G FLEXIBLE USE WITH PWS740/PWS745 COMPONENTS PWS750 SINGLE-CHANNEL CONNECTION Typical Connection for Internal Oscillator Operation NOTES: (1) User option. (2) Use TN0604 for 5V to ±15V operation. (3) Multichannel Operation. Duplicate for multichannel operation with PWS750-2U. ©1988 Burr-Brown Corporation PDS-838F Printed in U.S.A. April, 1997 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

At TA = 25°C; +VIN = +15V; and IOUT = ±15mA balanced loads, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS PWS750-1U OSCILLATOR Frequency: Internal OSC TTLIN = 0V 725 800 875 kHz External OSC 2.5 MHz Supply: 15V Operation V 5V Operation 4.5 5.5 V T, T Drive Current mApk T, T Drive Voltage, High V Low 0.7 V TTLIN, IIH nA IIL µA VIH V VIL 0.8 V TTLOUT, IOL mA PWS750-2U +VIN TO ±VOUT ISOLATION TRANSFORMER ISOLATION Voltage Rated Continuous AC 60Hz 750 Vrms 100% Test (1) 60Hz, 1s, <5pC PD 1200 Vrms Barrier Impedance 1012 || 8 Ω || pF Leakage Current at 60Hz VISO = 240Vrms 1.5 µArms Winding Ratio Primary/Secondary PWS750-3U DIODE BRIDGE Reverse Recovery IF = IR = 50mA ns Reverse Breakdown IR = 100µA V Reverse Current VR = 40V 1.5 µA Forward Voltage IF = 100mA 1.8 V PWS750-4U +5VIN to ±15VOUT ISOLATION TRANSFORMER ISOLATION Voltage Rated Continuous AC 60Hz 750 Vrms 100% Test (1) 60Hz, 1s, <5pC PD 1200 Vrms Barrier Impedance 1012 || 8 Ω || pF Leakage Current at 60Hz VISO = 240Vrms 1.5 µArms Winding Ratio Primary/Secondary TEMPERATURE RANGE Specification +70 Operating Derated performance –40 +85 Storage –40 +85 NOTES: (1) Tested at 1.6 x rated, fail on 5pC partial discharge leakage current on five successive pulses at 60Hz. 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.

T VD +VIN 16-Pin SO Double-Wide Surface Mount Enable Gnd TTLOUT TTL IN T PWS750-1U PIN CONFIGURATIONS AC AC 8-Pin SO Surface Mount PWS750-3U PWS750-2U PWS750-4U 8-Pin DIP Surface Mount NC AC Gnd AC NC TO VD TO ABSOLUTE MAXIMUM RATINGS PWS750-XU Basic Model Number Components 1U : High-Frequency Driver 2U, 4U : Isolation Transformer 3U : High-Speed Monolithic Diode Bridge

ORDERING INFORMATION

PACKAGE INFORMATION

NUMBER(1) PWS750-1U 16-Pin SOIC 211 PWS750-2U 8-Pin Plastic 226 PWS750-3U 8-Pin SO 182 PWS750-4U 8-Pin Plastic 226 NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book.

TYPICAL PERFORMANCE CURVES TA = +25°C, VIN = 15VDC, ILOAD = ±15mA unless otherwise noted. PWS750-4U LINE REGULATION 5.3 5.2 5.1 4.9 4.8 4.7 ±V (V) OUT Input (V) 4.6 5.4 PWR750-2U LINE REGULATION ±V (V) OUT Input (V) PWR750-2U AND PWS70-4U LOAD LINES ±V (V) OUT Load (mA) PWS750-2U PWS750-4U OUTPUT RIPPLE VOLTAGE 0.2 0.4 0.6 0.8 Filter Capacitance (µF) Ripple Voltage (mVp-p) Ripple Frequency = Oscillator Frequency 0.1 EFFICIENCY/LOAD CURVE Efficiency (%) PWS750-4U

4 Channel

Load Current (±mA) TTL SIGNAL DUTY CYCLE IN 100 % Duty Cycle 1.5 2.5 Synchronization Frequency (MHz) (= Twice the FET Drive Frequency) DC = % tH t + t H L tH tL Acceptable Duty Cycle Nominal Operating Frequency Synchronization Frequency (MHz) (= Twice the FET Drive Frequency)

The PWS750 components are basic building blocks to be used with other standard components to build an isolated push-pull DC/DC converter. The oscillator runs at 800kHz nominal, making it possible to reduce the size of the trans- former and lower the output ripple voltage. PWS750-1U OSCILLATOR PIN FUNCTIONS TTLIN is used to control the driver frequency with an external TTL level frequency source. The input frequency must be twice the desired driver frequency, since there is an internal divide-by-2 circuit to produce a 50% duty cycle output. The input duty cycle can vary from 12% to 95% (see Typical Performance Curves). When in the free running mode, the TTLIN pin must be tied to ground. TTLOUT is used when it is desired to synchronize the outputs of multiple PWS750-1Us to minimize beat frequency prob- lems. A standard open collector output is provided, therefore a 330Ω to 3.3kΩ pull-up resistor will be necessary depend- ing on stray capacitance on the sync line. A maximum of eight PWS750-1Us can be connected without the use of an external TTL buffer. An Enable pin is provided so that the driver (T, T) can be shut down to minimize power use if required. A TTL low applied to the pin will shut down the driver within one cycle. A TTL high will enable the driver within one cycle. The TTLOUT will still have an 800kHz signal when a master driver is disabled, so other synchronized drivers will not be shut down. The pin can be left open for normal operation. The +VIN pin supplies power to the oscillator. The VD pin connects the power to the transformer through the internal overcurrent sense resistor. The other end of the overcurrent sense resistor is tied to +VIN. A 0.3µF bypass capacitor must be connected to the VD pin to reduce the ripple current through the shunt resistor; otherwise false current limit conditions can occur due to ripple voltage peaks. TYPICAL PERFORMANCE CURVES (CONT) TA = +25°C, VIN = 15VDC, ILOAD = ±15mA unless otherwise noted. During overload conditions the output drive shuts off for approximately 80µs, then turns back on for 20µs, resulting in a 25% power up duty cycle. If the overload condition still exists, then the output will shut off again. When the fault or the excessive load is removed, the converter resumes normal operation. The T and T pins are the complementary FET drive outputs and are tied directly to the corresponding FET gate. The connection must be as short as possible. For multiple chan- nel operation they cannot be located above any ground or power planes, because capacitive loading will not allow fast enough charging of the FET gate. PWS750-2U AND PWS750-4U TRANSFORMER PIN FUNCTIONS On the primary side the VD pin of the PWS750-2U is tied directly to the VD pin of the PWS750-1U. Remember to place a 0.1µF capacitor as close to the PWS750-2U VD pin as possible. The TO and TO pins are connected to the drains of the corresponding FETs, whose sources are connected to ground. On the secondary side of the transformer, the Gnd pin is tied directly to the isolated ground. AC pins are 800kHz square wave signals at twice the output voltage, and are connected directly to the corresponding pin on the PWS750-3U. Pins 2 and 4 can be interchanged for ease of hook up. The connection to the diode bridge must be as direct as possible to minimize radiated noise. The winding ratio for the PWS750-2U is 1:1. This means that the output would normally be less than the input due to voltage drops in the FETs, transformer and diode bridge. Since the DC/DC converter is operating at 800kHz, the transformer is starting to operate close to the resonant frequency, which causes the output to increase in magni- tude. OUTPUT VOLTAGE DRIFT WITH A ±15mA LOAD 15.5 15.25 14.75 14.5 –25 100 Temperature (°C) V (V) OUT TTLIN Frequency (MHz) 1.5 1.6 ±VOUT (V) THE OUTPUT VOLTAGE CAN BE ADJUSTED ±3% BY VARYING THE DRIVER FREQUENCY 15.5 14.5

FIGURE 1. Sample PC Board Layout, 4:1.

pins to minimize series inductance and therefore noise. sample layout is shown in Figure 1. will generate little radiated noise if the traces are kept short. currents (>100mA) are needed to turn on the gates. the input current will be at least 120mA. TABLE I. MOSFET Selector Guide. FIGURE 2. MOSFET Driver Booster Circuits.

protect the FETs from high inrush currents during turn on. ing the VD pin of the PWS750-2U directly to the supply. FIGURE 3. Four-Channels of ±10V Signal Isolation with Channel-to-Channel Isolation.

3 Turns

once the barrier voltage is reduced to the rated value. FIGURE 5. A PWS750 Driver Can Be Used to Boost the Input Voltage to 15V to Power a PWS726 From a 5V Supply. FIGURE 4. A Complete ±10V Signal Acquisition System Operating From a Single 5V Supply.