LMZ23610

LMZ23610/8/6 and LMZ22010/8/6 Current Sharing Evaluation Board LMZ23610/8/6 and LMZ22010/8/6 Current Sharing Evaluation Board Introduction The LMZ23610/8/6 and LMZ22010/8/6 SIMPLE SWITCHER® power modules are easy-to-use DC-DC solution capable of driving up to a 10, 8 or 6 ampere load. They are available in an innovative package that enhances thermal performance and allows for hand or machine soldering. The LMZ23610/8/6 can accept an input voltage rail between 6V and 36V and the LMZ22010/8/6 can accept an input voltage rail between 6V and 20V. The current sharing evaluation board is designed so that four modules can be easily connected to supply up to a 40 amp load. More can be connected as long as care is taken to not exceed the current capabilities of the banana plug connectors and the 5-amp per pin rating of the edge board connector. The current sharing evaluation board is highly configurable. The output voltage can be changed to 5V, 3.3V, 2.5V or 1.2V with a jumper change. The external soft-start capacitor facilitates a controlled and adjustable startup rise time of the output. The board temperature can be measured with the onboard resistor. The UVLO can be adjusted by adding one resistor. To simplify the synchronization of the modules an onboard 555 timer provides an adjustable frequency clock from 350 to 600 kHz. The LMZ23610 and LMZ22010 family is a reliable and robust solution with the following features: loss-less cycle-by-cycle valley current limit to protect for over current or short-circuit fault, thermal shutdown, input under-voltage lockout, and will start up into a pre-biased output. National Semiconductor Application Note 2093 Marc Davis-Marsh April 7, 2010 Board Specifications • • • VIN = 6V to 36V (LMZ23610/8/6) VIN = 6V to 20V (LMZ22010/8/6) VOUT = 1.2V, 2.5V, 3.3V or 5V (minimum input voltage of 7V required for 5V output) • IOUT = 0 to 10, 8, or 6 Amps • θJA = 8.8 °C / W, θJC = 1.0 °C/W • Designed on four layers; Inner are 2 oz copper; Outer are 2 oz copper. • Measures 3.54" x 3.54" (90 mm x 90 mm) and is 62 mils (1.57 mm) thick of FR4 laminate material For additional circuit considerations, including additional output voltage options, refer to the Applications Section section of the LMZ23610/8/6 or LMZ22010/8/6 data sheets. For negative output voltage connections see AN-2027. Simplified Schematic AN-2093 30138708 FIGURE 1. © 2011 National Semiconductor Corporation 301387 www.national.com AN-2093 Test Connections The board should be connected to a power supply and load as shown below in Figure 2. The EN post is connected to the UVLO circuit on the back of the board. There is a resistive divider implemented on the board, with the bottom resistor unpopulated, that can be used to establish a precision UVLO level of the board. A common user change to this circuit is to adjust the value of RENT and RENB to adjust the operating UVLO to that of the target application. Refer to the respective data sheet for calculation. Note that if in the end application the EN pin voltage does not exceed 5.5V at maximum Vin, then the enable clamp zener D1 can be omitted. Pull EN low to shutdown the module and clock circuitry. The SYNC post is connected to the output of a 555 timer on the back of the board and is fed to the SYNC pin of the device. This clock is provided to simplify the testing of the current sharing features of the device and is not required for stand alone operation. The frequency of the clock can be adjusted from 350kHz to 600kHz using the potentiometer labeled R_freq_adj. Jumper J3 (SLAVE) can be used to disable the 555 timer and allow the use of external clocks from 314 to 600 kHz. Board Connection Diagram 30138701 FIGURE 2. www.national.com 2 AN-2093 Edge Connector Diagram 30138706 FIGURE 3. The evaluation board is also compatible with the 44-pin edge connector shown in Figure 3. The table below explains the functionality of the pins. Pin 1, 2, 3, 4, 5, 7, 8 9, 10, 11, 12, 13, 14, A, B, C, D, E 15, 16, 18, 19, 20, 21, 22, V, W, X, Y, Z H M T N J Name VIN GND VOUT Description Input supply — Nominal operating range is from 6V to 20V for the LMZLMZ22010/8/6 and from 6V to 36V for the LMZLMZ23610/8/6. Power Ground — Electrical path for the power circuits within the module. Output Voltage — Regulated 5, 3.3, 2.5 or 1.2V. VIN SENSE + VIN SENSE - Positive Kelvin Sense of Input voltage — Tied to VIN pin of the LMZ module. Negative Kelvin Sense of Input voltage — Tied to PGND (EP) of the LMZ module. VOUT SENSE + Positive Kelvin Sense of Output voltage — Tied to Vout banana jack. VOUT SENSE - Negative Kelvin Sense of Output voltage — Tied to AGND of the LMZ module. SYNC + Synchronization Positive Input — This is the positive probe point for viewing the clock generated by the 555 timer and is connected to the SYNC pin of the LMZ module. If the 555 timer is shutdown using J3 then an external clock can be used. The external clock must provide a CMOS logic level square wave whose frequency is between 314 kHz and 600 kHz. Synchronization Negative Input — Tied to AGND of the LMZ module. Share Positive Input — Connect this pin to the share pin of other LMZ modules to share the load between the devices. Share Negative Input — Tied to AGND of the LMZ module. Enable — Input to the precision enable comparator of the LMZ Module. Also tied to a pull-up resistor to enable the 5v bias supply and the 555 timer. L R P K S SYNC SHARE + SHARE EN TEMP SENSE Connected to top of the Rts temperature sensing resistor. Temperature measurements can be made by measuring the temperature dependant resistance between TEMP SENSE and VIN SENSE -. Convert the resistance to temperature with the following equation: Temperature (C) ≊ 2.6245 x Resistance (Ω) - 262.7 3 www.national.com AN-2093 Adjusting the Output Voltage The output voltage of the evaluation board is adjusted to either 5V, 3.3V, 2.5V, or 1.2V by moving jumper J1. For other voltage options see the datasheet for adjusting the feedback resistors. Current Sharing Current sharing is easy to evaluate. The next steps should be implemented only while the power to the device is off. Select which board will be the master. This is usually the board closer to the load. Connect the master board as described above in Test Connections. Insert the slave board into the socket on the master. If there is no socket, connect a 44pin board-edge extender to the top of the master board and solder the pins. The board-edge connector will connect Vin, Gnd, Vout, Enable, Sync and the Share pin between the boards to split the current demand between multiple boards. On the slave board(s) remove the jumper J1 (MASTER) and move it to jumper J2 (SLAVE). This disconnects the FB pin of the slave converter(s) (J1) and disables the clock that is pro- vided on the slave board (J2). The slave module's switching frequency will now be controlled by the clock on the master board. Turning the R_freq_adj pot counter clockwise lowers the clock frequency and turning the pot clockwise increases the frequency. By placing an additional jumper on J3 (SLAVE) of the master board, the 555 timer is disabled on both boards. With the clock disabled you can observe the parts performance when the devices are not synchronized, or you can supply an external clock through the SYNC post. J3 must be in place (555 disabled) on all boards to use an external clock on sync. The Sync pin of the slave can also be disconnected from the master board by removing the RSHORT resistor. This allows the user to provide a multiphase clock of their choosing to the boards. The advantage to running the clocks out of phase is to reduce the current stress on the input and output capacitors. For two modules the clocks should be run 180 degrees out of phase, for three modules the clocks should be run 120 degrees out of phase an so on. Although local input bypass capacitors are still required, the bulk capacitance required for a given ripple voltage can be greatly reduced. Output Voltage Ripple with Two Boards Synchronized to Output Voltage Ripple with Two Boards Synchronized with 350Khz 180° Phase Shift 30138709 30138710 FIGURE 4. www.national.com 4 AN-2093 Master Slave Connection 30138702 FIGURE 5. 5 www.national.com AN-2093 30138707 FIGURE 6. Evaluation Board Schematic www.national.com 6 AN-2093 TABLE 1. Current Sharing Evaluation Board Bill of Materials, VIN = 6V to 36V (20V), VOUT = 1.2 / 3.3V / 5V, IOUT (MAX) = 10/08/06A Designator U1 U2 U3 Description SIMPLE SWITCHER® Timer, 8-pin Narrow SOIC, Pb-Free 300 mA/600 mA up to 42V Input Step-Down DC/DC Regulator 0.047uF, X7R, 50V Case Size TO-PMOD-11 TSSOP-8 SOT23 Manufacturer National Semiconductor National Semiconductor National Semiconductor Kemet Manufacturer P/N LMZ23610/08/06 or LMZ22010/08/06 LMC555CM/NOPB LM2841XMK-ADJL/NOPB Quantity 1 1 1 Cin1 Cin6 Co1 Co5 Cin_b Cin2 Cin3 Cin4 Cin5 Co2 Cout_b Co3 Co4 Cff Css Cbt Cbyp, Cbyp2 Ct D1 D2 D3 Rent Rrst2 Rsync Renb Rtop Rbtm Rfbb Rfbt_1.2 Rfbt_1.2b Rfbt_2.5 Rfbt_2.5b Rfbt_3.3 Rfbt_3.3b Rfbt_5 Rfbt_5b RFB_LP Rpull Rshrt Rts 0805 C0805C473K5RACTU 4 10 µF, X7S, 50V 1210 TDK C3225X7S1H106M 4 150 µF, Aluminum Electrolytic, 50V 47uF, X5R, 10V 330µF, 6.3V, 0.015 ohm, 4700 pF, X7R, 50V 0.15uF, X7R, 10V 0.1uF, X7R, 50V 470pF, C0G/NP0, 50V 4.7V, 500mW Diode, Schottky, 40V, 1A Diode, Schottky, 20V, 1A 1.0k ohm, 5%, 0.125W G 1210 2917 0805 0603 0805 0805 SOD-123 SMA SOD_123FL 0805 Panasonic Murata Kemet Kemet Murata TDK AVX Vishay Diodes Inc. ON Semiconductor Vishay-Dale EEE-FK1H151P GRM32ER61A476KE20L T520D337M006ATE015 C0805C472K5RACTU GRM188R71A154KA01D C2012X7R1H104K 08055A471FAT2A MMSZ4688-V-GS08 B140-13-F MBR120LSFT1G CRCW08051K00JNEA 1 2 2 1 2 2 1 1 1 1 1 Not Populated 5.62k ohm, 1%, 0.125W 1.02k ohm, 1%, 0.125W, 1.07k ohm, 1%, 0.125W 576 ohm, 1%, 0.125W 9.53 ohm, 1%, 0.125W 3.74k ohm, 1%, 0.125W 84.5 ohm, 1%, 0.125W 8.06k ohm, 1%, 0.125W 169 ohm, 1%, 0.125W 5.6k ohm, 1%, 0.125W 73.2 ohm, 1%, 0.125W 20 Ω 200 ohm, 1%, 0.125W 0 ohm, 5%, 0.125W 100 ohm,Temp Sense Resistor 0805 0805 0805 0805 0805 0805 0805 0805 0805 0805 0805 0805 0805 0805 0805 0805 Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay CRCW08055K62FKEA CRCW08051K02FKEA CRCW08051K07FKEA CRCW0805576RFKEA CRCW08059R53FKEA CRCW08053K74FKEA CRCW080584R5FKEA CRCW08058K06FKEA CRCW0805169RFKEA CRCW08055K60FKEA CRCW080573R2FKEA CRCW080520R0FKEA CRCW0805200RFKEA CRCW08050000Z0EA PTS08051B100RP 100 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 7 www.national.com AN-2093 Designator R_freq_adj R2 R3 L2 Description ADJ, 100K ohm, 0.5W 3.48k ohm, 1%, 0.125W Inductor, Shielded Drum Core, Ferrite, 22uH, 0.7A, 0.155 ohm Test Point, TH, Miniature, Red Test Point, TH, Miniature, Black Banana Jack Connector Case Size Round - 0.350" Dia x 0.150" H 0805 SMD Manufacturer Bourn Vishay-Dale Wurth Elektronik Manufacturer P/N 3352T-1-104LF CRCW08053K48FKEA 744043220 Quantity 1 2 1 SYNC EN GND GND GND GND VIN VOUT J1 Keystone Electronics Keystone Electronics Keystone Electronics 5000 5001 575-8 2 2 6 Header, 4x2, Gold plated, 230 mil above insulator Header, 2x1, Gold plated, 230 mil above insulator Shunt, 100mil, Gold plated, Black Machine Screw, Round, #4-40 x 1/4, Nylon, Philips panhead Standoff, Hex, 0.5"L #4-40 Nylon TH, 100mil Samtec Inc. TSW-104-07-G-D 1 J2 J3 SH-1 SH-2 SH-3 H1 H2 H3 H4 H5 H6 H7 H8 J4 Rrst1 TH, 100mil Samtec Inc. TSW-102-07-G-S 2 Amp 382811-6 3 B and FFastener Supply NY PMS 440 0025 PH 4 Keystone 1902C 4 44-Pin Edge Connector Not Populated EDAC 305-044-555-201 1 0 www.national.com 8 AN-2093 Performance Characteristics Efficiency, VOUT = 5.0V 100 90 EFFICIENCY (%) 80 70 60 50 40 0 1 10 Vin 12 Vin 16 Vin 20 Vin 2345678 OUTPUT CURRENT (A) 9 10 30138720 Thermal Derating, VOUT = 5.0V 12 10 8 6 4 2 0 -40 -20 0 20 40 60 80 100 120 AMBIENT TEMPERATURE (°C) 30138721 10A 8A Startup, VIN = 12V, VOUT = 3.3V 30138722 PCB Layout Diagrams Gerber and CAD files can be downloaded from the associated product folder. 9 OUTPUT CURRENT (A) www.national.com AN-2093 30138714 FIGURE 7. Top Layer www.national.com 10 AN-2093 30138715 FIGURE 8. Internal Layer I (Ground) Heat Sinking Layer 11 www.national.com AN-2093 30138716 FIGURE 9. Internal Layer II (Routing) Heat Sinking Layer www.national.com 12 AN-2093 30138717 FIGURE 10. Bottom Layer (Ground and Routing) Heat Sinking Layer 13 www.national.com AN-2093 30138718 FIGURE 11. Top Silkscreen www.national.com 14 AN-2093 30138719 FIGURE 12. 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