DEMO MANUAL DC1977A-A/B LTC4121EUD/LTC4121EUD-4.2 400mA Synchronous Buck Battery Charger Description Demonstration circuit 1977A is the demonstration board for LTC®4121EUD-4.2/LTC4121EUD, a 400mA Synchronous Buck Battery Charger. The DC1977A supports the Maximum Power Point Tracking (MPPT) feature on the LTC4121EUD, for use with Photovoltaic (PV) cells or highly resistive sources. batteries with the maximum power available from the PV cell. It is also used if the power supply is highly resistive, such as applications that are at the end of very long wire runs. Design files for this circuit board are available at http://www.linear.com/demo FEATURED PART DC1977A-A LTC4121EUD-4.2 (Fixed Output) DC1977A-B LTC4121EUD (Adjustable Output) L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. The LTC4121EUD is typically used with PV cells to charge Performance Summary Specifications are at TA = 25°C SYMBOL PARAMETER CONDITIONS MIN TYP IN DC1977A Input Voltage I(IN) < 800mA 4.4 40 V PVIN DC1977A PV Cell Input I(IN) < 800mA 5 40.5 V V(BAT) DC1977A BAT Pin Voltage RFB2 = 1.40MΩ, RFB1 = 1.05MΩ 2.4 4.25 V I(BAT) DC1977A BAT Pin Current V(BAT) = 3.7V, DC1977A(R5) = 3.01kΩ, JP1 (“MPPT”) = ‘OFF’ 370 400 mA 385 MAX UNITS Typical Application LTC4121 Efficiency vs VIN at VFLOAT = 8.4V High Efficiency, Wide Input Voltage Range Charging with LTC4121 RMPPT1 787k + – VIN VBAT + 200mV TO 40V RPROG 3.01k LTC4121 FB FREQ GND FBG RFB1 1.05M RFB2 1.40M 200mA, PROG = 6.04k 400mA, PROG = 3.01k 95 SW CHGSNS BAT PROG CINTVCC 2.2µF CBOOST 22nF LPS4018-333ML MPPT RMPPT2 121k 97 INTVCC BOOST CBAT 47µF EFFICIENCY (%) CIN 10µF IN RUN 93 91 89 + Li-Ion 87 dc1977a F01 VBAT = 8.3V 5 10 15 20 25 VIN (V) 30 35 40 dc1977afa 1 DEMO MANUAL DC1977A-A/B assembly test Procedure Refer to Figure 1 for the proper measurement equipment setup and jumper settings and follow the procedure below. . 4.Turn PS2 off, move connection to point B, and turn PS2 on. NOTE. When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the VCC or VIN and GND terminals. See Figure 2 for proper scope probe technique. 5.Verify that VM1 indicates less than 4V, and then verify that AM1 indicates between 380mA ~ 400mA. Verify that VM2 shows 2.15V ~ 3.5V. The source impedance of the power supply is now ≈ 16Ω. But this impedance still allows delivering full charge current without engaging the MPPT feature. 1.Set JP1 (“MPPT”) to ‘ON’, set PS1 to 3.6V and turn on. 6.Turn PS2 off, move connection to Point C, and turn PS2 on. 2.Connect PS2 to point A, set to 15V and turn on. 3.Verify that VM1 indicates less than 4V, and then verify that AM1 indicates 380mA ~ 400mA. Verify that VM2 shows 14V ~ 14.5 V. There is only a series diode between PV+ and the VIN pin of the LTC4121. The purpose of this diode is prevent backfeeding a PV cell, if connected. A single diode Vf is insufficient to activate the MPPT feature, and the LTC4121 delivers full charge current to the battery. – C AM2 – B 82.4Ω 2W 7.Verify that VM1 indicates less than 4V, and then Verify that AM1 indicates 100mA ~150mA. Verify that VM2 shows 10V ~ 11V. The source impedance of the power supply is now 98Ω. The MPPT feature has engaged and the charge delivered to the battery has been reduced to allow VIN to stay at the programmed MPPT point. 8.Set JP1 (“MPPT”) to ‘OFF’, test is finished. 15.8Ω 2W + + + PS2 15V POWER SUPPLY 0.25A – A VM2 – – + – + PS1 3.6V POWER SUPPLY 1A – AM1 3.6Ω + VM1 – Figure 1. DC1977A Equipment Setup 2 dc1977afa DEMO MANUAL DC1977A-A/B assembly test Procedure Figure 2. Measuring Input or Output Ripple Note: All connections from equipment should be Kelvin connected directly to the board pins which they are connected on this diagram and any input or output leads should be twisted pair. theory of operation The LTC4121EUD-4.2/LTC4121EUD is a 4.4V ~ 40V input buck topology battery charger with Maximum Power Point Tracking (MPPT) for use with PV cells or highly resistive power supplies. The buck topology charger uses current mode for stable operation. LTC4121EUD ENABLE The LTC4121 can be enabled or disabled via the “RUN” pin, and this functionality can be accessed via JP2, the “RUN” jumper. When JP2 is in the “ENABLE” position, R3 and R4 (see schematic) ensure that the LTC4121 is not enabled until VIN is greater than 4.4V. Buck Charger The heart of the LTC4121EUD is the buck topology charger. The buck topology charger is a synchronous current mode regulator with N-channel FETs. The use of N-channel FETs optimizes die area, and only requires a single external 0.022µF capacitor for boostrapping the high side gate drive. The LTC4121EUD can charge up to 4 Li-Ion batteries in series, and has a maximum float voltage of 18V. The LTC4121EUD-4.2 is optimized for charging a single Li-Ion battery, and has a fixed float voltage of 4.2V. The buck inductor does not terminate in a capacitor, as in a buck voltage regulator, but rather goes through a small on-die metal resistor for current measurement, and then goes back out to the BAT pin. The battery is connected to the BAT pin, this allows the LTC4121EUD to measure not only the cycle by cycle current, but also the average current. The cycle by cycle current is used by the current mode buck regulator, and the average current is the battery charge current as programmed by Rprog. On the DC1977A, Rprog = 3.01kΩ, so I(BAT) = 400mA, if the MPPT function does not reduce the current. The buck regulator thus acts as a current source when the battery is in the constant current (CC) charging region and as a classic voltage output buck regulator when the battery is in the constant voltage (CV) charging region. In the constant voltage region, the battery becomes the output capacitor. If no battery is present, please ensure that the capacitors documented in the data sheet are installed on the board, to provide charge storage for the buck regulator. The battery charge current is programmed by Rprog = 3.01kΩ. The equation for battery charge current is: R_prog = h_prog • (V_prog/I_(chg)) = 988 • 1.227V/0.4 = 3.01kΩ dc1977afa 3 DEMO MANUAL DC1977A-A/B theory of operation The LTC4121EUD provides a switching frequency select pin, FREQ, to select between 750kHz and 1.5MHz; this function is accessed by JP4, the “FREQ” jumper. Figure 3 shows various nodes of interest with VIN = 5V, and the switching frequency at 750kHz (T = 1.333µs), The duty cycle is 86% for V(BAT) = 3.6V, this is not the 72% duty expected from a buck regulator. When the battery voltage is 3.6V, the charger is in constant current mode, so the control loop is making the effective output of the buck regulator the voltage necessary to push 400mA into the battery. This “effective” voltage is 5 X 0.86 = 4.3V, is the voltage necessary to ensure that a 400mA average current is flowing through the on-die metal sense resistor. Figure 4 shows the same nodes as Figure 3, but with VIN = 40V, and still at 750kHz. The duty cycle is ≈ 200ns/1.333µs, or 15%, but the period is 2.7µs. This is because the LTC4121 minimum on time was greater than that needed to achieve 4.3V, and the LTC4121 starts to pulse skip to get the necessary average duty cycle. The average duty cycle is 300ns/2.667µs = 11%. This produces an “effective” output voltage of 4.3V, so that the battery charges at 400mA. Figure 3. Normal Operation, Zoom, VIN = 5.1V, DK. Blue = VIN, Grn = ICHARGE, LT. Blue = VSW, Pk. = INTVCC, 750kHz Maximum Power Point Tracking (MPPT) The LTC4121EUD provides a Maximum Power Point Tracking (MPPT) function for use with PV cells or highly resistive power supplies. The MPPT pin allows programming of the MPPT point as a percentage of the Open Circuit VIN (VOC). To access this functionality the demo board provides JP1, the “MPPT” jumper, and R1 and R2. It is important to note that the disabled position for MPPT is the MPPT pin at VIN. To enable set the MPPT point as a fraction of VOC, based on the equation: Figure 4. Normal Operation, Zoom, VIN = 40V, DK. Blue = VIN, Grn = ICHARGE, LT. Blue = VSW, Pk. = VBOOST, 750kHz VMPPT 0.1(k +1) =[ ] VOC k where RMPPT2 = k • RMPPT1. So for the demo board, k = 121/787 = 0.154, and VMPPT/VOC = 0.75 • VOC. When MPPT is enabled (not equal to VIN), the LTC4121EUD periodically disconnects the load, and measures VIN no load = VOC. It then increases the load on VIN to meet charger demand, until the VMPPT threshold is reached, after which it no 4 dc1977afa DEMO MANUAL DC1977A-A/B theory of operation longer increases the load. This allows the MPPT voltage divider to set the desired MPPT point as a percentage of the no load VIN: Figure 5 shows the LTC4121EUD operating into a source impedance of 98Ω so the LTC4121 draws more power from VIN than is available. The MPPT pin of the LTC4121EUD sets the MPPT point to 0.75 of the open circuit voltage. First VOC is determined by removing all loads and letting VIN rise to VOC. The power drawn from VIN is increased until the VIN falls to the MPPT point, 0.75 • VOC = 0.75 • 15V = 11.25V. The resolution of the MPPT DAC is 330mV, thus this example has the MPPT point at 11V. The LTC4121 stops drawing power at this point, and the charge current (green) never exceeds 200mA, even though the Rprog value was chosen for 400mA. Figure 6 shows the same system, but the source impedance was lowered to 16Ω, consequently the full power needed to meet the requirements of Rprog is available before VIN falls to the MPPT voltage. Figure 5. MPPT Test, DK. Blue = VIN (Through 98Ω), Green = IL, LT. Blue = V(SW), k = 0.15, VMPPT/VOC = 0.75 Battery capacitors C1 and C2 The maximum float voltage for the LTC4121EUD is 18V, but for the LTC4121EUD-4.2, it is 4.2V. Linear recommends 47µF of capacitance on the BAT pin, if the battery is missing. For the LTC4121EUD the voltage rating of the capacitor will need to be 25V, so two 22µF, 25V, MLCC capacitors are used. In the case of the LTC4121EUD-4.2, a 6.3V capacitor will suffice and a single 47µF, 6.3V, MLCC capacitor is used for C1, with C2 as a no load. Figure 6. MPPT Test, DK. Blue = VIN (Through 16Ω), Green = IL, LT. Blue = V(SW), k = 0.15, VMPPT/VOC = 0.75 dc1977afa 5 DEMO MANUAL DC1977A-A/B Parts List ITEM QTY REFERENCE DC1977A General Bill of Materials Required Circuit Components 1 1 C3 2 1 C4 3 1 C5 4 1 L1 5 1 R1 6 1 R2 7 1 R3 8 1 R4 9 1 R7 Additional Demo Board Circuit Components 1 1 D1 2 1 M1 3 2 R5, R9 4 1 R6 5 2 R8, R10 6 1 R13 7 1 R14 8 1 R15 Hardware: For Demo Board Only 1 7 E1, E2, E3, E6, E7, E10, E11 2 3 4 5 4 0 4 4 E4, E5, E8, E9 J1-OPT JP1-JP4 JP1-JP4 ITEM QTY REFERENCE DC1977A-A Bill of Materials Required Circuit Components 1 0 R11 2 1 R12 3 1 U1 Additional Demo Board Circuit Components 1 1 C1 2 0 C2 ITEM QTY REFERENCE DC1977A-B Bill of Materials Required Circuit Components 1 1 R11 2 1 R12 3 1 U1 Additional Demo Board Circuit Components 1 2 C1, C2 6 PART DESCRIPTION MANUFACTURER/PART NUMBER CAP, CHIP, X7R, 0.022µF, ±10%, 50V, 0402 CAP, CHIP, X5R, 10µF, ±10%, 50V, 1210 CAP, CHIP, X5R, 2.2µF, ±20%, 6.3V, 0402 IND, SMT, 33µH, 420mΩ, ±20%, 0.80A, 4mm × 4mm RES, CHIP, 787kΩ, ±1%, 1/16W, 0402 RES, CHIP, 121kΩ, ±1%, 1/16W, 0402 RES, CHIP, 261kΩ, ±1%, 1/16W, 0402 RES, CHIP, 324kΩ, ±1%, 1/16W, 0402 RES, CHIP, 3.01kΩ, ±1, 1/16W, 0402 TDK, C1005X7R1E223K TAIYO-YUDEN, UMK325BJ106KM-T MURATA, GRM155R60J225ME15D COILCRAFT, LPS4018-333ML VISHAY, CRCW0402787KFKED VISHAY, CRCW0402121KFKED VISHAY, CRCW0402261KFKED VISHAY, CRCW0402324KFKED VISHAY, CRCW04023K01FKED DIODE, SCHOTTKY, 40V, 2A, PowerDI123 MOSFET, P-Channel, –30V, –5.9A, 45mΩ, SOT-23 RES, CHIP, 10kΩ, ±1%, 1/16W, 0402 RES, CHIP, 2kΩ, ±5%, 1/16W, 0402 RES, CHIP, 0Ω jumper, 1/16W, 0402 RES, CHIP, 47kΩ, ±5%, 1/16W, 0402 RES, CHIP, 5.1kΩ, ±1%, 1/16W, 0402 RES, CHIP, 100kΩ, ±5%, 1/16W, 0402 DIODES, DFLS240L VISHAY, Si2343CDS VISHAY, CRCW040210K0FKED VISHAY, CRCW04022K00JNED VISHAY, CRCW04020000Z0ED VISHAY, CRCW040247K0JNED VISHAY, CRCW04025K10JNED VISHAY, CRCW0402100KJNED TURRET, 0.09 DIA MILL-MAX, 2501-2-00-80-00-00-07-0 TURRET, 0.061" CONN, 3 Pin Polarized HEADER, 3 Pin, SMT, 2mm SHUNT, 2mm MILL-MAX, 2308-2-00-80-00-00-07-0 HIROSE, DF3-3P-2DSA SULLIN, NRPN031PAEN-RC SAMTEC, 2SN-BK-G PART DESCRIPTION MANUFACTURER/PART NUMBER No Load RES, CHIP, 0Ω jumper, 1/16W, 0402 40V 400mA SYNCHRONOUS STEP-DOWN BATTERY CHARGER, 3mm × 3mmQFN16 VISHAY, CRCW04020000Z0E LINEAR TECH., LTC4121EUD-4.2#PBF CAP, CHIP, X5R, 47µF, ±10%, 16V, 1210 CAP, CHIP, X5R, 47µF, ±10%, 16V, 1210 MURATA, GRM32ER61C476KE15L MURATA, GRM32ER61C476KE15L PART DESCRIPTION MANUFACTURER/PART NUMBER RES, CHIP, 1.40MΩ, ±1%, 1/16W, 0402 RES, CHIP, 1.05MΩ, ±1%, 1/16W, 0402 40V, 400mA SYNCHRONOUS STEP-DOWN BATTERY CHARGER, 3mm × 3mmQFN16 VISHAY, CRCW04021M40FKE VISHAY, CRCW04021M05FKED LINEAR TECH., LTC4121EUD#PB CAP, CHIP, X5R, 47µF, ±10%, 16V, 1210 MURATA, GRM32ER61C476KE15L dc1977afa Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 1 2 3 4 E2 E1 PROG NTC E5 E4 PV- or Vin- E3 4.4V - 40V 0.4A Vin+ PV+ R6 2.0k 5% 4 4 D1 DFLS240L ON OFF MPPT JP1 R2 121k R1 787k JP4 EXT NTC INT R9 10.0k R8 0 Ohm JUMPER FREQ RUN ENABLED DISABLED 3 1.5 MHz 10.0k 750 kHz R5 INTVCC R4 324k R3 261k 3 JP3 JP2 R7 3.01k BATSNS/FB PROG 10 13 5 GND 3 IN 17 EPAD 2 THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. R15 100k 5% GEORGE B. SCALE = NONE NC PCB DES. APP ENG. DATE: N/A SIZE 7 - 9- 14 IC NO. R12 1.05M 0 Ohm C1 C2* C2 OPEN CHRG FAULT GND 1 SHEET 1 LTC4121EUD - 4.2 / LTC4121EUD DEMO CIRCUIT 1977A - A / B OF 1 3 REV. 40V 400mA SYNCHRONOUS STEP-DOWN BATTERY CHARGER 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 www.linear.com Fax: (408)434-0507 LTC Confidential-For Customer Use Only BAT GND ENTC J1 OPT DF3-3P-2DSA R10 0 Ohm JUMPER 1 2 3 BAT 2.7V - 18V 400mA E6 GND E7 E8 E9 E10 VIN 4.4V - 40V GEORGE B. E11 DATE 7 - 9- 14 APPROVED 22µF/25V 22µF/25V 47µF/16V TECHNOLOGY 1.40M TITLE: SCHEMATIC LTC4121EUD R11 OPEN * C1 R12 TO BE CONNECTED TO C2 & C3 PRODUCTION FAB 3 1 DESCRIPTION REVISION HISTORY REV U1 R12 * R13 47k 5% - ECO LTC4121EUD - 4.2 APPROVALS -B ASSY -A * R14 5.1k 5% M1 Si2343DS C5 2.2µF 20% 6.3V INTVCC R11 * L1 33.0uH 25V C3 0.022µF LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. CUSTOMER NOTICE 11 9 NC/FBG 8 BAT 4 1 2 15 14 CHGSNS sw INTVcc BOOST FAULT CHRG UNLESS NOTED: RESISTORS: OHMS, 0402, 1%, 1/16W CAPACITORS: uF, 0402, 10%, 50V NTC MPPT FREQ RUN 12 6 7 16 U1 LTC4121EUD-4.2 / LTC4121EUD C4 10µF 50V 1210 2 1 2 3 4 DEMO MANUAL DC1977A-A/B Schematic Diagram dc1977afa 7 DEMO MANUAL DC1977A-A/B DEMONSTRATION BOARD IMPORTANT NOTICE Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations. If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES. The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or agency certified (FCC, UL, CE, etc.). No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind. LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive. Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and observe good laboratory practice standards. Common sense is encouraged. This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer. Mailing Address: Linear Technology 1630 McCarthy Blvd. Milpitas, CA 95035 Copyright © 2004, Linear Technology Corporation 8 dc1977afa Linear Technology Corporation LT 1214 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2014