MAX17595 Evaluation Kit Evaluates: MAX17595 as Flyback Converter

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1 General Description The MAX7595 evaluation kit (EV kit) is a fully assembled and tested circuit board that contains MAX7595 peakcurrent-mode controller for a flyback regulator. The EV kit is configured for an isolated 5V DC output voltage that can supply up to.5a current. The line input voltage range is from 85V AC to 65V AC or V DC to 75V DC. The EV kit demonstrates low quiescent current and efficiency up to 86%. This high efficiency is achieved by using a single-transistor (MOSFET) flyback converter topology that operates at khz switching frequency. The surface-mount transformer has a tertiary winding to power the IC after startup. An optocoupler, along with the transformer, provides galvanic isolation up to 500VRMS. Warning: The EV kit is designed to operate with high voltages. Dangerous voltages are present on this EV kit and on equipment connected to it. Users who power up this EV kit or the power sources connected to it must be careful to follow safety procedures appropriately to work with high-voltage electrical equipment. Under severe fault or failure conditions, this EV kit may dissipate large amounts of power, which could result in the mechanical ejection of a component or of component debris at high velocity. Operate this EV kit with care to avoid possible personal injury. Features S 85V AC to 65V AC or V DC to 75V DC Input Range S 5V DC at.5a Isolated Output Voltage S Galvanic Isolation Up to 500VRMS S khz Switching Frequency S Efficiency Up to 86% S Low-Cost Flyback Design S Proven PCB Layout S Fully Assembled and Tested Ordering Information appears at end of data sheet. Component List DESIGNATION QTY DESCRIPTION C 0.FF Q0%, 75V AC X plastic film capacitor (7mm x 5mm) Panasonic ECQ-UA4ML C 0I Q5% resistor (060) C, C, C8 0 C4 C5 Not installed, ceramic capacitors (060) C is short (PC trace); C, C8 are open 56pF Q5%, 50V C0G ceramic capacitor (060) Murata GRM885CH560J 0FF Q0%, 450V aluminum electrolytic capacitor (5mm diameter) Panasonic ECO-SGPCA DESIGNATION QTY DESCRIPTION C6, C C7 C8 C9 C 0.47FF Q%, 5V X7R ceramic capacitors (060) Murata GRM88R7E474K 0.FF Q%, 6V X7R ceramic capacitor (060) Murata GRM88R7C4K FF Q%, 5V X7R ceramic capacitor (060) Murata GRM88R7E5K 4.7FF Q%, 50V X7R ceramic capacitor (6) Murata GRMCR7H475K 00pF Q%, 50V X7R ceramic capacitor (0805) Murata GRMAR7EK For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit s website at ; Rev ; /4

2 Component List (continued) DESIGNATION QTY DESCRIPTION C C C6 4 C7 00pF Q%, 50V X7R ceramic capacitor (060) Murata GRM88R7HK FF Q%, 5V X7R ceramic capacitors () Murata GRMER7E6K 68nF Q%, 50V X7R ceramic capacitor (060) TDK C608X7RH68K C9 0 Not installed, capacitor (0805) C0 D D D D4 00pF Q0%, 50V X7R ceramic capacitor (mm diameter) TDK CD-EGAMYNS 600V,.5A bridge rectifier (DF-S) Diodes Inc. DF506S 0V, 00mA fast-switching diode (SOD) Diodes Inc. N448W-7-F 800V, A ultra-fast rectifier (SMA) Diodes Inc. USK-TP 00V, 6A ultra-fast recovery rectifier (5 PowerDI) Diodes Inc. PDU60- D5 0I Q5% resistor (6) L N R 6.8mH, 0.8A line filter (mm x mm) Würth Elektronik V, A n-channel MOSFET (DPAK) ST Micro STBNM80T4 I, A NTC thermistor (5mm) EPCOS B575S00M000 R R4 549kI Q resistors (6) R5 9.8kI Q resistor (060) DESIGNATION QTY DESCRIPTION R6 4.99kI Q resistor (060) R7, R8, R7 0 Not installed, resistors (6) R9 8.5kI Q resistor (060) R, R, R R5, R7 0 Not installed, resistors (060) R 49.9kI Q resistor (060) R ki Q resistor (060) R4 R6 40kI Q resistors (6) R8 0kI Q5% resistor (6) Panasonic ERJ-P08J4V R9 I Q resistor (060) R0 0I Q resistor (060) R 0.I Q resistor (6) Panasonic ERJ-8BSFR0V R 470I Q resistor (060) R6 4.99kI Q resistor (060) R8.49kI Q resistor (060) R9 I Q resistor (060) R0 0 Not installed, resistor (0805) T U U U *EP = Exposed pad. 80FH, 0.8A, :0.4:0. transformer (EFD5) Coilcraft MA5475-AL Peak-current-mode controller for flyback regulator (6 TQFN-EP*) Maxim MAX7595ATE+ Phototransistor (6 DIP) Avago 4N5-00E.4V, 0.5% shunt regulator ( SOT) Diodes Inc. TLV4BFTA PCB: MAX7595 EVALUATION KIT Component Suppliers SUPPLIER PHONE WEBSITE Coilcraft, Inc Diodes Incorporated EPCOS AG Murata Electronics North America, Inc Panasonic Corp STMicroelectronics TDK Corp Note: Indicate that you are using the MAX7595ATE+ when contacting these component suppliers.

3 Isolation transformer Variac Two voltmeters Warnings: Quick Start Required Equipment Exercise Caution when connecting and measuring off-line voltages. Voltage at the primary side can be as high as 700V DC. Wear eye protective gear at all times. Do not touch any part of the circuit with bare hands or conductive materials when powering up. Make sure that all high-voltage capacitors are fully discharged before handling. VOUT Setup Procedure The MAX7595 EV kit is fully assembled and tested. Follow these steps to verify board operation. Caution: Do not turn on the power supply until all connections are completed. ) Connect the positive lead of a DC voltmeter to the VOUT PCB pad. ) Connect the negative lead of a DC voltmeter to the GNDO PCB pad. ) Make sure that the isolation transformer is not powered up. Connect the variac to the output of the isolation transformer. 4) Connect one lead of an AC voltmeter to the wiper terminal of the variac. 5) Connect the other lead of the AC voltmeter to one of the fixed terminals of the variac. 6) Set the output voltage of the variac to 0V AC. 7) Connect the wiper terminal of the isolated variac to the AC PCB pad on the EV kit. 8) Connect the fixed tap of the isolated variac to the AC PCB pad on the EV kit. 9) Power up the isolation transformer and gradually increase the voltage of the variac to 85V AC and up to 65V AC. ) Verify that VOUT is 5V throughout the 85V AC to 65V AC input voltage range. Detailed Description of Hardware The MAX7595 EV kit evaluates MAX7595 off-line flyback converter operating in discontinuous-conduction mode (DCM), configured for a 5V DC,.5A output. This EV kit uses the peak current mode, pulse-width modulating (PWM) controller IC in a 6-pin TQFN package with an exposed pad. A simple RC charging circuit is used to start up the device. Bias winding feedback is used to supply power during normal operation. Input DC bus capacitor (C5) is designed based on 0Hz ripple content. The 0Hz ripple is chosen to be 5% at 85V AC and.5a load current. This PWM controller varies the duty cycle to compensate for the variation in VIN and the output load to maintain a constant output voltage. The duty cycle determines the on /off duration of the MOSFET (N). The n-channel MOSFET is used as a switch to control the current through the primary winding of transformer T. The duty cycle is controlled by the feedback loop consisting of voltage-divider resistors (R8, R9), a shunt regulator (U), an optocoupler (U), and the PWM comparator inside the IC. This network provides isolated-voltage-mode feedback, regulating the output voltage to 5V Q% with up to 500VRMS galvanic isolation. A thermistor (R) prevents high inrush currents present due to charging the input capacitor at startup. A snubber circuit (D, C, and R8) is used to prevent excessive drain voltages due to leakage inductance of the transformer. Current Limit The IC features current limiting for the transformer s primary side by monitoring the peak current through the sense resistor (R). Resistor R sets the EV kit circuit peak current (I PEAK ) to.5a. The IC turns off the N MOSFET when the peak current reaches the current limit. To reconfigure the peak current limit to a different value, use the following equation to choose a new R resistor: 05 R= mω I PEAK where I PEAK is in amps and R is in mi. Undervoltage Lockout and Overvoltage Protection The EV kit features a UVLO and OVI circuit that prevents operation below the programmed input supply startup voltage and above the overvoltage threshold. Resistors R R6 set the undervoltage and overvoltage thresholds. The circuit undervoltage and overvoltage thresholds are set at 60V AC (85V DC) and 74V AC (87V DC), respectively. To reconfigure the UVLO and OVI voltages, refer to the Startup Voltage and Input Overvoltage Protection Setting (EN/UVLO, OVI) section in the MAX7595/MAX7596/MAX7597 IC data sheet.

4 EN/UVLO and OVI PCB pads are available for monitoring the voltages present at the respective inputs. Soft-Start The EV kit provides an option to configure the circuit soft-start. Capacitor C7 configures the soft-start time (t SS ) to ms. To reconfigure the soft-start time to a different value, use the following equation to choose a new C7 capacitor: C7 = t SS nf where t SS is in ms and C7 is in nf. Switching Frequency The EV kit switching frequency is set to khz by resistor R9. To configure the IC s switching frequency to a different value, between 0kHz and MHz, use the following equation to choose a new R9 resistor: R9 = Ω fsw where f SW is in Hz and R9 is in I. Frequency Dithering The EV kit switching frequency can be dithered in a range of Q% to reduce EMI. There are two specifications for the frequency dithering: the frequency (how often) of dithering and the amount (how much) of dithering. Capacitor C configures the dither frequency using the following equation: 50µA C = F.V fdither where f DITHER is in Hz and C is in farads, and the dither frequency (f DITHER ) is recommended to be set close to khz. Resistors R9 and R configure the amount of dithering in percentage (%) of the switching frequency using the following equation: R9 %DITHER = R The EV kit is shipped with the frequency dithering disabled and the DITHER /SYNC pin shorted to by a 0I resistor installed on the C footprint. To set the desired frequency dither, replace capacitor C and install resistor R with the appropriate values. The DITHER /SYNC PCB pad is available for monitoring the signal at the DITHER/SYNC pin. 4

5 (PC TRACE) VDRV 0 EP N.C. SLOPE RT 4 DITHER/SYNC N.C. R9 NDRV CS 9 5 COMP OVI 6 6 FB 7 SS EN/UVLO VIN VDRV AC AC DITHER/SYNC EN/UVLO OVI R C 0.uF 75VAC R 549k R 549k R4 549k R5 9.8k R6 4.99k R8 R7 L 6.8mH ~ ~ 4 D R R9 8.5k DITHER/SYNC R C 0ohm + C5 L- 0uF 450V C4 56pF 50V R 49.9k C SHORT R5 40k R4 40k R7 C 0.47uF U MAX7595 R k VFB R6 IN D5 40k D C9 C 4.7uF 50V R8 0k C 00pF D C6 0.47uF C8 uf C 00pF C7 0.uF R0 0 R 0. N T R 470 D4 C9 R0 R U C0 00pF R4 C uf C4 uf GNDO R6 4.99k R5 R7 C7 68nF U C5 uf C8 C6 uf R8.49k R9 GNDO VOUT GNDO MAX7595 Evaluation Kit L- OVI EN/UVLO VIN DITHER/SYNC EN/UVLO OVI VIN IN VDRV VFB VIN VOUT VOUT Figure. MAX7595 EV Kit Schematic 5

6 .0 Figure. MAX7595 EV Kit Component Placement Guide Component Side.0 Figure. MAX7595 EV Kit PCB Layout Component Side 6

7 .0 Figure 4. MAX7595 EV Kit PCB Layout Solder Side 7

8 Ordering Information PART MAX7595EVKIT# #Denotes RoHS compliant. TYPE EV Kit 8

9 Revision History REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 0 5/ Initial release 4/ Updated Component List, EV kit specifications, and Figure 5 /4 Updated L supplier in Component List cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a product. No circuit patent licenses are implied. reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. 60 Rio Robles, San Jose, CA 954 USA Products, Inc. and the logo are trademarks of Products, Inc.