Evaluates: MAX V Output-Voltage Application. MAX17557EVKIT# Evaluation Kit. Quick Start. General Description. Features. Recommended Equipment

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1 Click here for production status of specific part numbers. MAX7557EVKIT# Evaluation Kit General Description The MAX7557 5V-output evaluation kit (EV kit) provides a proven design to evaluate the MAX7557 high-voltage, high-efficiency, synchronous step-down DC-DC controller. The EV kit provides 5V/A at the output from a 6.5V to 6V input supply. The switching frequency of the EV kit is preset to 5kHz for optimum efficiency and component size. The EV kit features Enable/UVLO Input, selectable PWM/DCM modes, resistor-programmable UVLO threshold, adjustable soft-start time, open-drain PGOOD output, and overcurrent and overtemperature protection. Features Operates from a 6.5V to 6V Input Supply 5V Output Voltage Up to A Output Current 5kHz Switching Frequency Enable/UVLO Input, Resistor-Programmable UVLO Threshold Selectable PWM/DCM Modes of Operation Adjustable Soft-Start Time Programmable Soft-Stop Enable or Disable Function Open-Drain PGOOD Output Overcurrent (OCP) and Overtemperature (OTP) Protection Proven PCB Layout Fully Assembled and Tested Quick Start Recommended Equipment MAX7557 5V-output EV kit 6.5V to 6V, A DC-input power supply Load capable of sinking A Digital voltmeter (DVM) Procedure The EV kit is fully assembled and tested. Follow the steps below to verify the board operation. Caution: Do not turn on power supply until all connections are completed. ) Set the power supply at a voltage between 6.5V and 6V. Disable the power supply. ) Connect the positive terminal of the power supply to the V IN PCB pad and the negative terminal to the nearest PGND PCB pad. Connect the positive terminal of the A load to the PCB pad and the negative terminal to the nearest PGND PCB pad. ) Connect the DVM across the PCB pad and the nearest PGND PCB pad. 4) Place the shunt on the jumpers JU, JU, JU, and JU4 according to the intended operation (see Tables,,, and 4 for details). 5) Turn on the DC power supply. 6) Enable the load. 7) Verify that the DVM displays 5V. Ordering Information appears at end of data sheet. 9-68; Rev ; /8

2 Detailed Description of Hardware The MAX7557 5V-output evaluation kit (EV kit) is a proven design to evaluate the MAX7557 high-voltage, high-efficiency, synchronous step-down DC-DC controller. The EV kit provides 5V/A at the output from a 6.5V to 6V input supply. The switching frequency of the EV kit is preset to 5kHz for optimum efficiency and component size. The EV kit features current sensing using either an external current-sense resistor for accuracy or an inductor DCR for improved system efficiency. Current foldback limits MOSFET power dissipation under shortcircuit conditions. The MODE/SYNC PCB pad allows an external clock to synchronize the device. Jumper JU allows the selection of the mode of operation based on light load-performance requirements. The EV kit includes an PCB pad and jumper JU to enable the output at a desired input voltage. A PGOOD PCB pad is available for monitoring when the converter output is in regulation. Setting the Input Undervoltage Lockout Level The pin can be open or pulled up to a voltage between.5v and 5.5V to turn on the controller. Figure shows the possible configurations. The pin can be used as input undervoltage lockout detector with a typical hysteresis of mv. As shown in Figure, the input voltage at which the controller of the IC turns on, can be set with a resistordivider connected to from IN to GND. Select R = kω and calculate R based on the following equation: (VIN_UVLO.5) R = R.5 where V INUVLO is the input voltage at which the controller should be enabled. See Table for JU jumper settings and descriptions of controller enable/undervoltage lockout (). 4.5V TO 6V IN MAX7557 VIN_MIN TO VIN_MAX R IN MAX7557 R ALWAYS-ON CONFIGURATION ABLE AS INPUT UVLO VIN_MAX / VIN_MIN V TO 6V IN VIN_MIN TO VIN_MAX IN MAX7557 R MAX7557 >.5V D 4.7V R TURN ON/OFF BY LOGIC SIGNAL ABLE AS INPUT UVLO VIN_MAX / VIN_MIN 4.4 Figure. Setting the Input Under Voltage Lockout Maxim Integrated

3 Table. JU: MODE/SYNC Selection JUMPER SHUNT POSITION MODE/SYNC PIN MAX7557_MODE JU - Connected to V CCINT DCM Mode of Operation - Connected to GND PWM Mode of Operation Table. JU: Overcurrent Protection Mode Select JUMPER SHUNT POSITION ILIMSEL MODE JU Table. JU: Controller Enable/Under Voltage Lock Out () Description JUMPER SHUNT POSITION MAX7557 OUTPUT JU - Connected to V CCINT Latch-off Mode - Connected to GND Foldback Mode Not installed Unconnected Enabled Connected to the input UVLO Enabled, UVLO level is set by the - divider midpoint. resistor divider from V IN to GND. - Connected to GND Disabled MODE/SYNC The device s Mode Selection and External Synchronization (MODE/SYNC) pin can be used to select the PWM or DCM modes of operation. The logic state of the MODE/ SYNC pin is latched when the V CCINT and voltages exceed the respective UVLO rising thresholds and all internal voltages are ready to allow LX switching. State changes on the MODE/SYNC pin are ignored during normal operation. Refer to the MAX7557 IC data sheet for more information on the PWM and DCM modes of operation. Table lists JU jumper settings that can be used to configure the desired mode of operation. The internal oscillator of the device can be synchronized to an external clock signal on the MODE/SYNC pin. The external synchronization clock frequency must be between. x f SW and.4 x f SW, where f SW is the frequency of operation set by R. The minimum external clock high pulse width should be greater than 5ns. Adjusting Output Voltage The output voltage of the converter is set by connecting a resistor-divider to FB from the output to GND (Figure ). Select R using the following equation, based on the offset introduced on the output voltage by the FB leakage. Let α be the offset introduced on the output voltage: α R I FB_ MAX7557 VOUT R FB R4 Figure : Adjusting Output Voltage where: α = offset introduced on the output voltage I FB = FB leakage current (±na max) For example, for = 5V, α =.% of (= 5mV). R 5kΩ Calculate R4 with the following equation: R R4 = VOUT.8 Maxim Integrated

4 Soft-Start Capacitor Selection Soft-start time is programmed by connecting a capacitor from the SS pin to GND. An internal 5µA current source charges the capacitor at the SS pin providing a linear ramping voltage for output-voltage reference. The softstart time is calculated based on the following equation:.8v tss = CSS 5µA Soft-Stop Enable (SSTP): The device s soft-stop enable pin (SSTP) enables or disables the soft-stop functionality during device s power down using the pin. Soft-stop time is equal to soft-start time, which can be programmed by connecting a capacitor from the SS pin to GND. Connect the SSTP pin to V CCINT or GND to enable or disable the soft-stop function, respectively. Table 4 lists JU4 jumper settings that can be used to configure the soft-stop feature. Frequency Selection (RT) The selection of switching frequency is a tradeoff between efficiency and component size. Low-frequency operation increases efficiency by reducing MOSFET switching losses and gate-drive losses, but requires a larger inductor and/or capacitor to maintain low output-ripple voltage. The switching frequency of the device can be programmed between khz and.mhz using the RT pin. Connect a resistor from RT to GND to set the regulator s switching frequency. Leave RT open for the default 5kHz frequency. The following formula can be used to find the required resistor for a given switching frequency. 9 RRT =.7 fsw where R RT is in kω and f SW is in khz. Leaving the RT pin open causes the device to operate at the default switching frequency of 5kHz. Table 4. JU4: SSTP Selection JUMPER SHUNT POSITION MODE/SYNC PIN MAX7557 CONDITION JU4 - Connected to V CCINT ABLE Soft-Stop Function - Connected to GND No Soft-Stop Function Maxim Integrated 4

5 MAX7557 EV Kit Performance Report V IN = 4V, V SSTP = GND unless otherwise noted. EFFICCY (%) EFFICICY vs. LOAD CURRT V IN = 6.5V V IN = V V IN = 4V V IN = 6V V IN = 6V V IN = 48V toc OUTPUT VOLTAGE (V) V IN = 6.5V LOAD AND LINE REGULATION V IN = V V IN = 48V V IN = 4V V IN = 6V V IN = 6V toc EFFICICY (%) EFFICICY vs. LOAD CURRT (5PUT, DCM MODE) V IN = V V IN = 6.5V V IN = 4V V IN = 6V V IN = 48V toc V IN = 6V LOAD CURRT (A) LOAD CURRT (A) LOAD CURRT (A) OUTPUT VOLTAGE (V) V IN = 6.5V LOAD AND LINE REGULATION (5PUT, DCM MODE) V IN = V V IN = 48V V IN = 6V LOAD CURRT (A) V IN = 4V V IN = 6V toc4 V /UVLO I OUT V PGOOD SOFT-START/SHUTDOWN FROM /UVLO ms/div CONDITIONS: A LOAD CURRT toc5 V/div A/div Maxim Integrated 5

6 MAX7557 EV Kit Performance Report (continued) V IN = 4V, V SSTP = GND unless otherwise noted. SOFT-START/SHUTDOWN FROM /UVLO toc6 SOFT-START WITH.5V PREBIAS, toc7 V /UVLO V /UVLO V/div V/div I OUT A/div V PGOOD ms/div CONDITIONS: A LOAD CURRT, V SSTP = V CCINT V PGOOD ms/div LOAD TRANSIT RESPONSE toc8 LOAD TRANSIT RESPONSE toc9 (AC-Coupled) mv/div (AC-Coupled) mv/div I LOAD 5A/div I LOAD 5A/div 4µs/div CONDITIONS: LOAD CURRT STEPPED FROM A TO 5A µs/div CONDITIONS: LOAD CURRT STEPPED FROM 5A TO A (AC-Coupled) I LOAD LOAD TRANSIT RESPONSE (5PUT, DCM MODE) 4µs/div toc CONDITIONS: LOAD CURRT STEPPED FROM.A TO 5A mv/div 5A/div GAIN (db) - - BODE PLOT, 5PUT CONDITIONS: A LOAD CURRT GAIN CROSSOVER FREQUCY = 4 khz PHASE MARGIN = 64.4 PHASE toc - k k k FREQUCY (Hz) PHASE ( ) Maxim Integrated 6

7 Component List SUPPLIER WEBSITE Coilcraft, Inc. Murata Americas Panasonic Corp. Renesas Electronics Diodes Inc. Note: Indicate that you are using the MAX7557 when contacting these component suppliers. Ordering Information PART MAX7557EVKIT# TYPE EVKIT MAX7557 EV System Bill of Materials No. Description Quantity Designator Part Number.µF %, V,X7R,Ceramic capacitor (6) C,C MURATA GRM88R7A4KA5 4.7µF %, 8V,X7R,Ceramic capacitor () C,C4 MURATA GRMER7K475ME4 5µF,%,8V,ELECT,mm C5 PANASONIC EEV-FKK5Q 4 µf %, 6V,X7R,Ceramic capacitor (6) C6 MURATA GRM88R7C5KA 5 µf %, V,X7R,Ceramic capacitor (85) C7 MURATA GGRMBR7A6KE5 6 5pF,%,5V,X7R,4,Ceramic capacitor(4) C8 MURATA GRM55R7H5KA 7.47µF,%,6V,X7R, Ceramic capacitor(6) C9 MURATA GRM88R7C474KA88 8.µF,%,5V,X7R, Ceramic capacitor(4) C MURATA GRM55R7H4KE4 9 8µF %, 6.V,X7R,Ceramic capacitor () C PANASONIC EEFSEJ8R µf %, V,X7R,Ceramic capacitor () C,C4 MURATA GRMDR7A6KA pf,%,v,x7r,4,ceramic capacitor(4) C5 MURATA GRM55R7AKA nf,%,5v,x7r,4,ceramic capacitor(4) C8 MURATA GRM55R7HJA88 pf,%,5v,x7r,4,ceramic capacitor(4) C9 MURATA GRM555CHGA 4 Diode PIV=V; IF=A D DIODES INCORPORATED DFLS-7 5 -pin header (6-pin header. centers ) 4 JU,JU,JU,JU4 Sullins: PECSAAN 6 INDUCTOR,.µH, 9.4A L COILCRAFT XAL77-ME 7 N-CHANNEL POWER MOSFET(LFPAK) PD-(45W); I-(5A); V-(6V) Q RESAS RJK65DPB-#J5 8 N-CHANNEL POWER MOSFET(LFPAK) D-(65W); I-(45A); V-(6V) Q RESAS RJK65DPB-#J5 9 RES+,Ω,%,4 8 R, R4, R7, R9, R-R4, R9 RES+,.Ω,%,4 R RES+,.5Ω,%,.5W, R8 TT ELECTRONICS LRMAT-R5F RES+,7.5KΩ OHM,%,4 R7 RES+,KΩ OHM,%,4 R8 4 RES+,95.KΩ OHM,%,4 R 5 RES+,7.8KΩ OHM,%,4 R 6 Buck Controller MAX7557ATP+ U MAX7557ATP+ Maxim Integrated 7

8 Maxim Integrated 8 MAX7557EVKIT# Evaluation Kit MAX7557 EV System Schematic 5V@A SGND C6 R5 R R R R6 JU JU JU JU4 VOUT C4 C C R9 R C C R R8 R VIN C5 C4 C C R C C7 R C6 L 4 5 Q R4 C7 R4 4 5 Q C A D C9 R9 R8 R U C8 C5 C8 C9 R7 R PGOOD MODE/SYNC C A D R6 R5.5.UF 8UF.UF PGND SGND SGND VIN VOUT VIN VIN VOUT UF PF 7.5K. 95.K 7.8K UF UF 4.7UF 4.7UF.5UF MAX7557 PF.UF.UF 5UF.UH UF K.47UF PGND PGND SSTPE EP VCCEXT IN DH BST LX DL PGND CSP CSN PGOOD FB COMP GND ILIMSEL MODE/SYNC RT SS S D G S D G + + +

9 MAX7557 EV System PCB Layout MAX7557 EV Kit Silk Top MAX7557 EV Kit Top MAX7557 EV Kit L-GND Maxim Integrated 9

10 MAX7557 EV System PCB Layout (continued) MAX7557 EV Kit L-GND MAX7557 EV Kit Bottom Maxim Integrated

11 MAX7557 5V Output Evaluation Kit Revision History REVISION NUMBER REVISION DATE 8/7 Initial release DESCRIPTION PAGES CHANGED /8 Changed the document title. Updated the following sections: General Description, Features, Quick Start, and Detailed Description of Hardware. Added Table and Table 4, and updated Table and Table. Updated the MAX7557 EV Kit Performance Report, the MAX7557 EV System Bill of Materials, the MAX7557 EV System Schematic, and the MAX7557 EV System PCB Layout. -.5 Corrected typo. 7 For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim Integrated s website at. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. 8 Maxim Integrated Products, Inc.