MIC79110 Evaluation Board Simple 1.2A Linear Li-ion Battery Charger General Description The Micrel MIC79110 is a simple and accurate Li-ion battery charger. Featuring a built-in pass transistor, precision programmable current limiting (±5%), precision voltage termination (±1% over temperature) and a very small package, the MIC79110 packs full functionality into a very small space. Other features of the MIC79110 include two independent end-of-charge indications including a digital indication that is programmable with a resistor-to-ground and an analog current output that is proportional to the output current, allowing for monitoring of the actual charging current. Additional features include very low dropout (550mV over the temperature range), thermal shutdown, and reverse polarity protection. In the event that the input voltage to the charger is disconnected, the MIC79110 also provides minimal reverse-current and reversed-battery protection. Available in both fixed 4.2V and adjustable outputs, the MIC79110 is offered in the leadless 10-pin 3mm × 3mm DFN with an operating junction temperature range of −40°C to +125°C. Datasheets and support documentation are available on Micrel’s web site at: www.micrel.com. Getting Started 1. Connect an external supply to VIN (J1) and GND (J2 or J6) terminals. With the output of the power supply disabled, set its voltage to the desired input test voltage (2.5V ≤ VIN ≤ 16V). An ammeter may be placed between the input supply and the VIN terminal. Be sure to monitor the supply voltage at the VIN terminal, as ammeter and/or power lead resistance can reduce the voltage supplied to the device. 2. Connect a Lithium-ion battery to VBAT (J3) and GND (J2 or J6) terminals. The load at the VBAT pin is the Lithium-ion battery. A voltage meter may be placed across VBAT and GND to monitor the output voltage. 3. Monitor the DEOC (J5) and AEOC (J7) Connect a voltage meter across DEOC and GND to monitor end of charge. To monitor the charging current, connect a voltage meter across AEOC and GND terminals. 4. Enable the SD pin (J4) Connect SD to GND terminal to initiate charging. Ordering Information Part Number Description MIC79110-4.2YML EV Evaluation Board Evaluation Board Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com May 28, 2013 Revision 2.0 Micrel, Inc. MIC79110 Evaluation Board SD – Shutdown Pin The MIC79110 comes with an active-high shutdown pin feature that allows the regulator to be disabled. Forcing the SD pin high disables the regulator and sends it into a “zero” off-mode-current state. In this state, current consumed by the regulator goes nearly to zero. Forcing the SD pin low enables the output voltage. This part is CMOS and the SD pin cannot be left floating; a floating SD pin may cause an indeterminate state on the output. VIN – Input Voltage Input voltage range is from 2.5V to 16V. Default bypass capacitor value is 2.2µF rated for maximum voltage of 16V for the input pin. ACHG – Analog Charge Indicator Output Output charge current for the MIC79110 can be monitored using the ACHG pin. The current sourced from this pin is 1/1000th of the output charge current. The evaluation board has R5 set to 1kΩ, so that the voltage measured at pin J7 is equal to the output current of the battery charger. On the evaluation board, the SD pin can be tied to the DEOC pin by installing a 0Ω resistor for R8 to place it in shutdown mode. The pin can also be tied to ground via R7 during test to keep the part on. The third option is tying it to J4 and controlling the shutdown pin externally. DEOC – Digital End of Charge Indicator This is an N-Channel open drain output on the MIC79110 that pulls high when the charge current falls below the minimum charge current that is set by REOC. Low indicates charging a current that is higher than the programmed current set by REOC. When the current drops to less than the programmed current set by REOC, the output goes high impedance, indicating end-of-charge. On the evaluation board, resistors R7 and R8 are left open. Shutdown can be toggled externally using pin J4. RSET – Current-Limit Sensing The MIC79110 features output current limit sensing from a range of 50mA to 1.2A. Current limit is set by an external resistor-to-ground by Equation 1: IRSET = (0.2/RSET) x 1000 The default setting on the evaluation board has the DEOC pin connected to VIN via R6 with a 10kΩ pull up resistor. There is also the option of connecting to the SD pin via R8. This will automatically turn off the part at the end of charge. Eq. 1 Default setting for the evaluation board is RSET = 165Ω with the current limit set at 1.21A. The DEOC pin can also be used to shut down the charger by using a resister divider with R7 and R8. Shutdown threshold is approximately 1.05V and for an output voltage of 4.2V, use Equation 3 to find the correct resistor values: SNS or ADJ – Output Voltage Setting The evaluation board comes with the fixed output version of the MIC79110. Output voltage is set at 4.2V and the SNS pin is shorted to the VBAT pin via R1 with a 0Ω resistor. VOUT R1 = +1 VSD R2 For the adjustable version of the MIC79110, the output voltage must be set with two external resistors R1 and R2. The reference voltage for the MIC79110 is 0.6V and VBAT is set by Equation 2: VBAT = 0.6 × (1 + (R1/R2)) Eq. 3 REOC – End of Charge Sensing The MIC79110 monitors the output charge current and indicates end of charge when the current drops below a minimum current. This minimum current is set by the resistor R4 that is connected to ground. Eq. 2 End of charge limit is set by R4 with Equation 4: VBAT – Lithium-ion Battery Lithium-ion battery is connected to this pin. Default evaluation board is set to charge 4.2V batteries. Bypass capacitor on the VBAT pin is 4.7µF. IREOC = (0.2/REOC) x 1000 Eq. 4 Default setting for the evaluation board is REOC = 4 kΩ, which calculates to an end of charge current of 50mA. May 28, 2013 2 Revision 2.0 Micrel, Inc. MIC79110 Evaluation Board PCB Layout Recommendations Top Layer Bottom Layer May 28, 2013 3 Revision 2.0 Micrel, Inc. MIC79110 Evaluation Board Bill of Materials Item C1 C2 Part Number Manufacturer GRM188R60J475KE19D Murata C1608X5R0J475K080AB TDK Description Qty. (1) (2) 4.7µF, 6.3V, X5R, 0603 1 2.2µF, 16V, X5R, 0805 1 0Ω, 1%, 1/10W, 0603 1 (3) 06036D475KAT2A AVX C2012X5R1C225K Murata C2012X5R1C225K125AA TDK 0805YD225KAT2A AVX CRCW06030000FRT1 R3 CRCW0603165RFKEA Vishay/Dale 165Ω, 1%, 1/10W, 0603 1 R4 CRCW06034021FRT1 Vishay/Dale 4.02kΩ, 1%, 1/10W, 0603 1 R5 CRCW06031001FRT1 Vishay/Dale 1kΩ, 1%, 1/10W, 0603 1 R6 CRCW06031002FRT1 Vishay/Dale 10kΩ, 1%, 1/10W, 0603 1 Simple 1.2A Linear Li-ion Battery Charger 1 U1 Vishay/Dale (4) R1 (5) MIC79110YML Micrel, Inc. Notes: 1. Murata: www.murata.com. 2. TDK: www.tdk.com. 3. AVX: www.avx.com. 4. Vishay: www.vishay.com. 5. Micrel, Inc.: www.micrel.com. MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2004 Micrel, Incorporated. May 28, 2013 4 Revision 2.0