® 724 QUAD ISOLATED DC/DC CONVERTER FEATURES APPLICATIONS ● QUAD ISOLATED ±8V OUTPUTS ● HIGH BREAKDOWN VOLTAGE: 3000V Test ● LOW LEAKAGE CURRENT: <1µA at 240V/60Hz ● LOW COST PER ISOLATED CHANNEL ● SMALL SIZE: 27.9mm X 27.9mm X 6.6mm (1.1'' X 1.1'' X 0.26'') ● ● ● ● ● MEDICAL EQUIPMENT INDUSTRIAL PROCESS CONTROL TEST EQUIPMENT DATA ACQUISITION SYSTEMS NUCLEAR INSTRUMENTATION DESCRIPTION The 724 converts a single 5VDC to 16VDC input into four pairs of bipolar output voltages of approximately half the output voltage. The converter is capable of providing a total output current of 128mA at rated voltage accuracy and up to 500mA without damage. The four output channels are isolated from the input and from each other. They may be connected independently, in series for higher output voltage, or in parallel for higher output current as a single channel isolated DC/DC converter. Integrated circuit construction of the 724 reduces size and cost. High isolation breakdown voltages and low leakage currents are assured by special design and construction which includes use of a high dielectric strength, and low leakage coating used on the internal assembly. A self-contained 800kHz oscillator drives switching circuitry, which is designed to eliminate the common problem of input current spiking due to transformer saturation or crossover switching. P+ Rectifiers and Filters +V01 C1 –V01 Rectifiers and Filters +V02 C2 –V02 Rectifiers and Filters +V03 C3 –V03 Rectifiers and Filters +V04 C4 –V04 V+ Oscillator and Switch Drivers V– International Airport Industrial Park • Mailing Address: PO Box 11400 Tel: (520) 746-1111 • Twx: 910-952-1111 • Cable: BBRCORP • • Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706 Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 © PDS-405A 1978 Burr-Brown Corporation Printed in U.S.A. October, 1993 SPECIFICATIONS ELECTRICAL At 25°C with VIN = 15V, R1 = 1.3kΩ, C = 0.47µF, unless otherwise noted. PARAMETER CONDITIONS INPUT Input Voltage Input Current TYP MAX UNITS 5 15 50 110 120 10 16 VDC mA mA mA mA, pk mA, pk ∑ IOUT = 24mA ∑ IOUT = 128mA, 25°C ∑ IOUT = 128mA, 25°C ∑ IOUT = 24mA, C = 0.47µF ∑ IOUT = 128mA, C = 0.47µF Input Ripple (1, 5) ISOLATION Test Voltage (2) Rated Voltage MIN 25 Input-to-Output, 5s min Channel-to-Channel, 5s min Input-to-Output, Continuous Channel-to-Channel, Continuous Input-to-Output Input-to-Output, 240V/60Hz (2) Isolation Impedance Leakage Current OUTPUT Voltage (3) Current for Rated Voltage Total Safe Nondestructive Current Load Regulation(3) Ripple Voltage (5) 125 3000 3000 1000 1000 1.0 VDC VDC VDC VDC GΩ || pF µA 9.0 8.3 128 V V mA 500 200 mA mA 10 || 6 At 15V Input IL = 3mA IL = 16mA Total of All Outputs Any One Output(4) Total of All Outputs Any One Output 8.0 7.5 8.5 7.9 3 (4) Difference of +VO and –VO Sensitivity to Input Voltage Change Output Voltage Change Over Temperature IL = 3mA IL = 16mA +IL = –IL 35 200 ±30 0.63 2 –25°C to +85°C TEMPERATURE RANGE Operating Storage –25 –55 mV, pk mV, pk mV V/V % °C °C +85 +125 NOTES: (1) 0.47µF external capacitor across “P+” to “V–” pins and 12'' of #24 wire to VIN. (2) See “Isolation Voltage Ratings” on page 5. The input to output and channel to channel continuous AC rating is 700Vrms. (3) See “Typical Performance Curves.” (4) A minimum output current of 3mA at each output is recommended to maintain output voltage accuracy. (5) Test bandwidth 10MHz, max. CONNECTION DIAGRAMS PACKAGE INFORMATION(1) Top View MODEL 724 +VO4 1 20 E C4 2 19 V+ –VO4 3 18 V– No pin present 4 17 P+ +VO3 5 16 No pin present C3 6 15 –VO1 –VO3 7 14 C1 No pin present 8 13 +VO1 +VO2 9 12 No pin present C2 10 PACKAGE PACKAGE DRAWING NUMBER 20-Pin 102A NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix D of Burr-Brown IC Data Book. 11 –VO2 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. ® 724 2 TYPICAL PERFORMANCE CURVES All specifications typical at 25°C, unless otherwise noted. DROPPING RESISTOR R1 vs INPUT VOLTAGE OUTPUT VOLTAGE vs INPUT VOLTAGE 2.0 16 Dropping Resistor, R1 (kΩ) Output Voltage (V) 14 12 10 ∑ IOUT = 24mA IL = ±3mA 8 6 4 ∑ IOUT = 128mA IL = ±16mA 2 1.5 1.0 0.5 Acceptable Range 0 0 0 10 5 15 20 0 10 15 20 Input Voltage, VIN (V) LOAD REGULATION (Single Channel with Balanced Load) LOAD REGULATION (Interchannel with Unbalanced Load) 9 8.5 Output Voltage +VOL, –VOL (V) 9 Output Voltage +VOL, –VOL (V) 5 Input Voltage (V) RF is chosen for IF = 3mA 8 RF is chosen for IF = 16mA 7.5 7 Test Condition 1 (Dual Output, Balanced Load) IF = 3mA 8.5 8 IF = 16mA 7.5 7 Test Condition 2 (Dual Output, Unbalanced Load) 6.5 6.5 0 10 30 20 40 0 50 10 TEST CONDITION 1 (Balanced Load) P+ P+ RL –VO1 +VO1 V+ E RL +VO2 R1 RF E IF V– RF C4 +VO3 IL RF 724 –VO2 +VO2 VIN IF RF RF V– +VO4 –VO4 C4 RF RF IF IF RF IF RF IF C3 IF IF RL IL C2 IF RF +VO4 –VO4 +VO1 V+ C3 –VO3 –VO1 IL RF –VO2 VIN 50 C1 RL IL C2 724 40 TEST CONDITION 2 (Unbalanced Load) C1 R1 30 20 Output Current, IL+ (mA) Output Current, IL+ = IL– (mA) –VO3 +VO3 RF IF IF IF ® 3 724 INSTALLATION AND OPERATING INSTRUCTIONS Each output is filtered with an internal 0.047µF capacitor. Output ripple voltage can be reduced below the specified value by adding external capacitors up to 10µF between each output and its common. Typical application connections for the 724 are shown in Figures 1 and 2. Primary power (VIN) is applied at the “P+” and “V–” terminals. The common or ground for VIN may be connected to either “P+” or “V–”, the only requirement is that “P+” and “V+” must be positive with respect to “V–”. DISCUSSION OUTPUT CURRENT RATINGS At rated output voltage accuracy, the 724 is capable of providing 128mA divided among its eight outputs(1). A minimum average output current of 3mA is recommended at each output to maintain voltage accuracy. Power for the internal oscillator and switch drivers is derived from the primary power by a voltage dropping resistor, R1. The value of R1 as a function of VIN is shown in the “Typical Performance Curves” section. Alternately, voltage for the “V+” terminal may be obtained from a separate source. “V+” should be +5VDC to +7.5VDC positive with respect to “V–”. If a separate source is used, the V+ input must be applied before the “P+” input to avoid possible damage to the unit. P+ and V+ must remain positive with respect to “V–” at all times (including transients). If necessary, diode clamps should be put across these inputs. Outputs channels(2) may be connected in series or parallel for higher output voltage or current. ISOLATION CONFIGURATIONS The fact that the four outputs of the 724 are isolated from the input and from each other allows both two-port and threeport isolation connections. The “E” pin enables the converter when connected to “V+” and disables it when connected to “V–”. Figure 1 shows two 3650 optically coupled isolation amplifiers connected in three-port configuration. Two of the 724 channels provide power to the 3650’s inputs. The other channels supply power to both 3650’s outputs. Each amplifier’s input and output are isolated from each other and the system’s power supply common. Isolation specification applies to the amplifier input-to-output voltage isolation specification. An external capacitor, “C” (0.47µF ceramic), is used to reduce input ripple. It should be connected as close to the “P+” and “V–” pins as practical. Input leads to these terminals should also be kept as short as possible. Since the 724 is not internally shielded, external shielding may be appropriate in applications where RFI at the 800kHz nominal oscillator frequency is a problem. +15VDC +VO1 P+ 3650 C1 1.3kΩ –VO1 V+ +VO2 E C2 VIN 0.47µF 1 COM V– –VO2 1 Power Supply Common 724 +VO3 1 2 3650 C3 Denote separate input common 1 and input common 2. –VO3 1 2 +VO4 Denote separate output common 1 and output common 2. C4 2 –VO4 2 FIGURE 1. Three-Port Isolation. ® 724 4 SHORT CIRCUIT PROTECTION The circuit in Figure 3 may be added to the input of the 724 to protect it from damage in situations where too much current is demanded from the outputs—such as a short circuit from an output to its common. The circuit limits input current to approximately 150mA for an input voltage of 15VDC (for β of 2N2219 of 50). Figure 2 illustrates how the 724 may provide isolated input power to the input stage of four 3650s connected in the twoport configuration. Power for the four output stages is provided by the system +15VDC and –15VDC supplies. Input stages are isolated from each other and from the system supply. In this situation, the 724’s isolation specification applies to amplifier’s input-to-output voltage and to the voltage existing between any two I/P COM terminals. NOTES: (1) “Output” denotes a single output terminal (+V or –V) and its associated common. (2) “Channel” denotes a pair of outputs (+V and –V) and their associated common. (3) Reference National Electrical Manufacturers Association (NEMA) Standards Parts ICS 1-109 and ICS 1-111. ISOLATION VOLTAGE RATINGS Since a “continuous” test is impractical in a product manufacturing situation (implies infinite test duration), it is generally accepted practice to perform a production test at a higher voltage (i.e., higher than the continuous rating) for some shorter length of time. P+ + The important consideration is then “what is the relationship between actual test conditions and the continuous derated maximum specification?” There are several rules of thumb used throughout the industry to establish this relationship. Burr-Brown has chosen a very conservative one: VTEST = (2 x VCONTINUOUS RATING) + 1000V. This relationship is appropriate for conditions where the system transient voltages are not well defined.(3) Where the real voltages are well defined or where the isolation voltage is not continuous the user may choose to use a less conservative derating to establish a specification from the test voltage. VIN 3.6kΩ R1 2N2219 IN4140 724 V+ 0.47µF E 100Ω 1Ω V– – FIGURE 3. Short Circuit Protection. +15VDC –15VDC 3650 3650 +15VDC –15VDC 4 O/P COM O/P COM C4 –VO4 +VO4 +15VDC –VO3 P+ C3 3 0.47µF +VO3 1.3kΩ V+ VIN 724 +VO2 E C2 C1 –VO1 –VO2 +VO1 2 V– O/P COM COM –15VDC 3650 +15VDC –15VDC +15VDC –15VDC 3650 1 O/P COM 1 2 3 4 Denote four separate input commons. O/P COM FIGURE 2. Two-Port Isolation with Four 3650s. ® 5 724