® RT9554A Battery Output Current Sense Protection IC General Description Features The RT9554A is designed for over-current detection. The current sense amplifier amplifies the voltage across resistor which is connected between CSP and CSN by 200. The amplified voltage is compared with the voltage of BAT_REF and check whether over-current happens or not. The RT9554A also provides a comparator with two input pins, AC_REAL and AC_REF for users. There is an output pin FLAG as an indicator which is a N-MOSFET in open-drain configuration. Users can connect one resistor between the FLAG pin and supply voltage. Either over-current condition occurs or the AC_REAL voltage is larger than the AC_REF voltage, the FLAG is pulled low. The RT9554A is a available in the WDFN-8L 2x2 package. Common Mode Input Range up to 24V VCC Operating Current : 200μA μA (under S3/S4/S5) VCC Shutdown Current : 5μ Programmable Over-Current Level FLAG Signal goes Low when OCP RoHS Compliant and Halogen Free Applications Notebooks Pin Configurations VCC EN FLAG AC_REF Ordering Information RT9554A Package Type QW : WDFN-8L 2x2 (W-Type) 9 8 7 6 5 CSP CSN BAT_REF AC_REAL WDFN-8L 2x2 Lead Plating System G : Green (Halogen Free and Pb Free) Marking Information Note : 2C : Product Code Richtek products are : 1 2 3 4 GND (TOP VIEW) 2CW RoHS compliant and compatible with the current require- W : Date Code ments of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. Simplified Application Circuit RSENSE Output Input 1.05V RT9554A FLAG CSN 3.3V CSP VCC 5V 0V EN BAT_REF AC_REAL AC_REF Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9554A-00 June 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT9554A Functional Pin Description Pin No. Pin Name Pin Function 1 VCC Power Supply Input. Connect this pin to 5V and place a minimum 0.1F decoupling capacitor .The decoupling capacitor should be placed to this pin as close as possible. 2 EN Enable Control Input. 3 FLAG Open-Drain Output. Connected to an external resistor. When over-current occurs, this pin will be pulled low. 4 AC_REF Comparator Inverting Input. 5 AC_REAL Comparator Non-Inverting Input. 6 BAT_REF Over-Current Threshold Setting. It is used to set over-current threshold from 0.4V to 2V. 7 CSN Negative Current Sense Input. 8 CSP Positive Current Sense Input. 9 (Exposed Pad) GND Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation Function Block Diagram POR + x 200 - CSP CSN VRON EN Comparator VCC + BAT_REF FLAG - Comparator AC_REAL + AC_REF - GND Operation The RT9554A consists of one current sensing amplifier and one comparator, and it provides the following functions : over-current protection and voltage comparison between AC_REAL and AC_REF. Users can connect one resistor between the FLAG pin and supply voltage. Either over-current condition or the occurs AC_REAL voltage is larger than AC_REF, the FLAG pin is pulled low. Over Current Protection BAT_REF voltage. If the output voltage of current sensing amplifier is larger than the BAT_REF voltage, the FLAG pin is pulled low. AC_REAL & AC_REF Comparison A comparator is designed for the voltage comparison between AC_REAL and AC_REF. If the voltage of AC_REAL is larger than AC_REF, the FLAG pin is pulled low. With 1mΩ order of resistor shunts between CSP and CSN, the current sensing amplifier amplifies the voltage between CSP and CSN by 200 and compares the result with the Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS9554A-00 June 2014 RT9554A Absolute Maximum Ratings (Note 1) CSP/CSN to GND --------------------------------------------------------------------------------------------------------- −0.3V to 26V VCC, BAT_REF, EN, AC_REAL, AC_REF, FLAG to GND ------------------------------------------------------- −0.3V to 6V Power Dissipation, PD @ TA = 25°C WDFN-8L 2x2 -------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) WDFN-8L 2x2, θJA --------------------------------------------------------------------------------------------------------WDFN-8L 2x2, θJC -------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Model) ---------------------------------------------------------------------------------------------MM (Machine Model) ----------------------------------------------------------------------------------------------------- Recommended Operating Conditions 2.19W 45.5°C/W 11.5°C/W 260°C 150°C −65°C to 150°C 2kV 200V (Note 4) High-Side Voltage, VCSP/VCSN -------------------------------------------------------------------------------------Supply Voltage, VCC ----------------------------------------------------------------------------------------------------Junction Temperature Range -------------------------------------------------------------------------------------------Ambient Temperature Range -------------------------------------------------------------------------------------------- 4.5V to 24V 4.5V to 5.5V −40°C to 125°C −40°C to 85°C Electrical Characteristics (VCC = 5V, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Unit 5 -- 24 V EN = High -- 50 -- A EN = Low -- -- 5 A CSN CSP Input Input Voltage Range V CSP, VCSN ICSN + ICSP VCC Input VCC Operating Current I VCC VCC > POR, EN = High -- 200 -- A VCC Shutdown Current I VCC_shd VCC > POR, EN = Low -- 2 5 A VCC POR Rising Voltage V IN_POR 2.8 -- 3.7 V -- 400 -- mV Rising Hysteresis Enable Enable Input Voltage Logic-High V IH 0.7 -- -- V Logic-Low V IL -- -- 0.3 V Current Sense Circuit System Response Time OCdelay OCP triggered -- 50 -- s OP Gain AV VCSP = VCSN = 12V -- 200 -- V/V Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9554A-00 June 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT9554A Parameter Symbol Min Typ Max Unit ISINK = 10mA -- -- 0.1 V VBAT_REF = 0.4V -- -- 15 % VBAT_REF = 0.8V -- -- 10 % VBAT_REF = 2V -- -- 5 % Ileak_FLAG EN Low -- -- 5 A BAT_REF Leakage Current Ileak_BAT_REF EN Low -- -- 5 A BAT_REF Input Range VBAT_REF 0.4 -- 2 V -- -- 10 mV FLAG Pull Low Voltage Input Current Sensing Accuracy FLAG Leakage Current CSacc Test conditions OCSET Comparator AC_REAL & AC_REF Comparator Comparator Offset VOS_AL_CMP AC_REAL Input Range VAC_REAL 0.3 -- 2 V AC_REF Input Range VAC_REF 0.3 -- 2 V -- -- 200 ns Comparator Response Time VAC_REAL = 0.3V to 2V VAC_REAL > VAC_REF FLAG go low Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect device reliability. Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is measured at the exposed pad of the package. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS9554A-00 June 2014 RT9554A Typical Application Circuit ISENSE Output Input 1.05V 0.001 RT9554A 7 0.1µF 10k CSN FLAG 0.1µF 3 3.3V 8 CSP 0.1µF R1 BAT_REF 2.2 1 5V VCC 0.1µF 1k 5V Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9554A-00 June 2014 AC_REAL 4 9 (Exposed Pad) EN 0.1µF From System R2 GND 2 6 5 From System AC_REF is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT9554A Typical Operating Characteristics FLAG Behavior FLAG Behavior AC_REF (1V/Div) AC_REF (1V/Div) AC_REAL (2V/Div) AC_REAL (2V/Div) FLAG (1V/Div) FLAG (1V/Div) AC_REF = 1V, AC_REAL from 0 to 5V Time (100ns/Div) Time (400ns/Div) FLAG Behavior FLAG Behavior I LOAD (5A/Div) I LOAD (5A/Div) BAT_REF (500mV/Div) BAT_REF (500mV/Div) FLAG (1V/Div) AC_REF = 1V, AC_REAL from 5 to 0V BAT_REF = 1V, ILOAD = 0A to 6A FLAG (1V/Div) BAT_REF = 1V, ILOAD = 6A to 0A Time (10μs/Div) Time (10μs/Div) Power On Mask Time Power Off from EN I LOAD (5A/Div) I LOAD (5A/Div) FLAG (2V/Div) FLAG (2V/Div) BAT_REF (900mV/Div) BAT_REF (500mV/Div) EN (5V/Div) BAT_REF = 1V, ILOAD = 0A to 6A Time (1ms/Div) Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 EN (5V/Div) BAT_REF = 1V, ILOAD = 0A to 6A Time (500μs/Div) is a registered trademark of Richtek Technology Corporation. DS9554A-00 June 2014 RT9554A OCP Accuracy Curve 0 -1 Accuracy (%) -2 -3 -4 -5 -6 -7 -8 -9 VIN = 12V, RS = 1mΩ -10 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 BAT_REF (V) Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9554A-00 June 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT9554A Application Information The RT9554A provides battery OCP protection functions with FLAG indicator to informs system. It can operate with minimized external components of switching power supply systems to achieve OCP protection. The overcurrent is detected by monitoring the differential voltage of input current sense resistor. The RT9554A provides a 50μs system response time for FLAG and there is a 3ms mask time after EN rising edge. Also, the RT9554A provides a comparator with two pins, AC_REAL and AC_REF for users. FLAG The FLAG is an open-drain output and requires a pull-up resistor. When over-current is detected, FLAG is pulled low within 50μs and maintain until OCP status releases. Over Current Protection( OCP) As an industry standard, high accuracy current sense amplifier is used to monitor the input current that flow through current sense resistor, The RT9554A detects CSPCSN differential voltage across the current sense resistor to monitor input current from battery. The OCP trigger point equation is shown as below : R2 R1 R2 ISENSE 0.001 200 = BAT_REF BAT_REF 3.3V 200 is the internal error amp AV. We suggest R1+ R2 = 100kΩ to avoid power consumption. Isense is over-current protection trigger point. For the overall timing sequence, please refer to Figure 1. Filter capacitor A 0.1μF capacitor between CSP and CSN for differential mode filtering is recommended. A 0.1μF capacitor between CSN and ground is for common mode filtering, and an optional 0.1μF capacitor between CSP and ground is for common mode filtering. The CSP and CSN pins are used to sense Rsense with default value of 1mΩ. However, resistors of other values can also be used. Using a larger sense resistor, can have higher regulation accuracy, but, it comes with higher conduction loss. Thermal Considerations For continuous operation, do not exceed absolute maximum junction temperature. The maximum power dissipation depends on the thermal resistance of the IC package, PCB layout, rate of surrounding airflow, and difference between junction and ambient temperature. The maximum power dissipation can be calculated by the following formula : PD(MAX) = (TJ(MAX) − TA) / θJA where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and θJA is the junction to ambient thermal resistance. For recommended operating condition specifications, the maximum junction temperature is 125°C. The junction to ambient thermal resistance, θJA, is layout dependent. For WDFN-8L 2x2 package, the thermal resistance, θJA, is 45.5°C/W on a standard JEDEC 51-7 four-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formula : PD(MAX) = (125°C − 25°C) / (45.5°C/W) = 2.19W for WDFN-8L 2x2 package VCC 3ms EN BAT_REF VOC The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curve in Figure 2 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. FLAG Figure 1. Timing Sequence Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 is a registered trademark of Richtek Technology Corporation. DS9554A-00 June 2014 RT9554A Maximum Power Dissipation (W)1 2.8 Four-Layer PCB Layout Considerations 1.6 Layout is very important for the RT9554A. If designed improperly, the PCB may radiate excessive noise. Certain points must be considered before starting a layout for the RT9554A. 1.2 Connect an RC low pass filter to VCC, 0.1μF, and 2.2Ω are recommended Connect a RC low pass filter to EN, 0.1μF, and 1kΩ are recommended. Place the filter capacitor close to the IC. Current sense connections must always be made using Kelvin connections to ensure an accurate signal with the current limit resistor located at the device. All sensitive analog traces and components such as CSP, CSN, VCC, EN and FLAG , should be placed away form high voltage switching nodes to avoid coupling. 2.4 2.0 0.8 0.4 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 2. Derating Curve of Maximum Power Dissipation Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS9554A-00 June 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT9554A Outline Dimension D2 D L E E2 1 e SEE DETAIL A b 2 1 2 1 A A1 A3 DETAIL A Pin #1 ID and Tie Bar Mark Options Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.700 0.800 0.028 0.031 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.200 0.300 0.008 0.012 D 1.950 2.050 0.077 0.081 D2 1.000 1.250 0.039 0.049 E 1.950 2.050 0.077 0.081 E2 0.400 0.650 0.016 0.026 e L 0.500 0.300 0.020 0.400 0.012 0.016 W-Type 8L DFN 2x2 Package Richtek Technology Corporation 14F, No. 8, Tai Yuen 1st Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries. www.richtek.com 10 DS9554A-00 June 2014