CAT7105 2.0A High Efficiency Step-Down DC/DC Converter CAT7105 2.0A High Efficiency Step-Down DC/DC Converter Features Application High Efficiency up to 95% 4.75V to 23V Wide Input Voltage Range Set-Top-Box, DVD, LCD Displays Battery Charger and High Power LED Power Output Adjustable from 1.23 to 21V 2.0A Output Current 380kHz constant Frequency Operation Current Mode Operation Supply Distributed Power System Data comm. xDSL CPE Over-temperature Protected Over Current Protection Under Voltage Lockout Pin Configuration 25µA Shutdown Current SOP8 Package RoHS Compliant (100% Green available) General Description The CAT7105 is a high efficiency and high output current step-down DC/DC converter that integrates a low resistance high side NMOS. Including on the substrate with the listed features are a high performance voltage error amplifier that provides tight voltage regulation accuracy under transient conditions; an under voltage Ordering Information Part Number Package Ship CAT7105CA 8L SOP (Green) 2500/ Tape & Reel lockout circuit to prevent start up until the input voltage reaches 4.75V; an internally set soft start circuit to limit inrush currents; and other features include an over current protection and thermal shutdown. The CAT7105 is available in a 8 pin SOIC package. The CAT logo is a registered trademark of Chip Advanced Technology 2007 Chip Advanced Technology Inc. – All Right Reserved. May-2007 Rev:0.94 2/12 CAT7105 Pin Description Pin Symbol Description High Side Gate Drive Boost Input. A capacitor must be connected from SW to BS. This capacitor 1 BS 2 VIN 3 SW 4 GND 5 FB 6 COMP 7 EN Enable Pin. This input provides an electrical ON/OFF control of the power Supply. 8 NC No Connection boosts the gate drive to the internal NMOS above VIN to fully turn it ON. Power Supply Pin. The input voltage for the power supply is connected to Pin2. Power Switch Output. This is the output of a power MOSFET switch connected directly to the input voltage. Ground Pin. This is the ground reference connection for all components in the power supply. Voltage Feedback Pin. This is the input to an error amplifier, which drives the PWM controller. It’s necessary to connect this pin to the actual output of power supply to set the DC output voltage. Compensation Pin. This pin is used to compensate the regulation control loop. Connect a series RC network from COMP pin to GND pin to compensate the regulation control loop. Function Block Diagram The CAT logo is a registered trademark of Chip Advanced Technology 2007 Chip Advanced Technology Inc. – All Right Reserved. May-2007 Rev:0.94 3/12 CAT7105 Typical Application C12 10nF R1 Vin=4.75V~23V Vout=1.23V*(1+R1/R2) R2 U1 FB 5 COMP 6 EN 7 SS 8 C7 NC C8 CAT7105 FB COMP EN NC GND SW VCC BST 4 3 2 1 D1 B320A L1 1 SW Vout 2 Vin C5 0.1uF C9 NC C1 10uF C6 22uF C2 10uF C3 NC C4 100uF C10 R3 BST 0.1uF R4 100K EN C11 0.1uF 2 Vin JP1 3 1 ON OFF *note: The recommended applications shall be customer design-in orientation to fit each customers demand. Based on the nature of customers demand-oriented, please contact CAT or agent for design support service. R2 R1 R3 C8 L1 V out=5V 68K 22K 15K 2nF 15uH V out=3.3V 16.8K 10K 10K 2nF 6uH V out=1.8V 4.7K 10K 5.6K 1nF 4.7uH The CAT logo is a registered trademark of Chip Advanced Technology 2007 Chip Advanced Technology Inc. – All Right Reserved. May-2007 Rev:0.94 4/12 CAT7105 Absolute Maximum Ratings Input Supply Voltage………………………….GND - 0.3V to +23V ESD Classification……………………..….…Class 2 SW Voltage …………………………………………- 0.3 to VIN+0.3V Junction Temperature Range ………………………… 150°C Other Pins …………. ………………..- 0.3V to +6V Operating Temperature ………..…….. -20 C to 85°C Boost Voltage ………..……………Vsw-0.3V to Vsw+6V Storage Temperature Range ………..-65 C to 150°C SW Peak Current ………………… ….3.0 A Lead Temperature (Soldering 10s) ……..……. 260°C o o *note: The IC has a protection circuit against static electricity. Do not apply high static electricity or high voltage that exceeds the performance of the protection circuit to the IC. Electrical Characteristic (Recommended Operating Conditions, Unless Otherwise Noted; VIN = 12V; TA = 25 oC)) Parameter Test Conditions Supply Voltage Shutdown Supply Current Regulated Feedback Voltage Error Amplifier Trans conductance Current sense to COMP Trans conductance Current Limit SW Leakage Current High Side On Resistance Low Side On Resistance Oscillation frequency Short Circuit Oscillation Frequency Min Typ. 4.75 VEN = 0V 4.75V≦VIN≦23V △ICOMP = ±10µA 1.19 500 25 1.23 800 Max Unit 23 V 50 1.26 1120 µA V µA/V 3.8 A/V 3.0 VEN = 0V, VSW = 0V 10 VFB=0V 0.25 10 380 40 Maximum Duty Cycle VFB=1.0V 90 Minimum Duty Cycle Under Voltage Lockout Threshold Under Voltage Lockout Threshold Hysteresis Thermal Shutdown Threshold VFB=1.5V VIN Rising EN High Level EN Low Level EN Input Current The CAT logo is a registered trademark of Chip Advanced Technology 2007 Chip Advanced Technology Inc. – All Right Reserved. I 320 3.9 4.1 440 % 0 4.3 1.1 % V 200 mV 160 ℃ 1.8 V V µA 2.6 VEN = 0V A µA Ω Ω KHz KHz 0.9 2.5 May-2007 Rev:0.94 5/12 CAT7105 Function Description The CAT7105 is a constant frequency current mode PWM step-down converter. It regulates Maximum Load current input voltages from 4.75V to 23V down to an output voltage as low as 1.23V, and is able to supply up to 2A of load current. voltage; however the maximum load current decreases at lower input due to large IR drop on the main switch and low side switch. The slope compensation signal reduces the peak Oscillator Frequency inductor current as a function of the duty cycle to prevent sub-harmonic oscillations at duty cycles greater than 50%. Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for superior load and line response The CAT7105 can operate down to 4.75V input and protection of the internal main switch and synchronous rectifier. The CAT7105 switches at a constant frequency (380 KHz) and regulates Enable the output voltage. During each cycle the PWM comparator modulates the power transferred to the load by changing the inductor peak current based on the feedback error the threshold voltage, the regulator starts operation and the internal slow start begins to ramp. If the EN pin voltage is pulled below the threshold, the regulator stops switching and the voltage. During normal operation, the main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the internal slow start resets. Connecting the pin to ground or to any voltage less than 0.9V will disable the regulator and activate the shutdown mode. peak inductor current is above the error voltage. When the main switch is off, the low side MOS will be turned on immediately and stay on until either the next cycle starts. Short Circuit Protection The CAT7105 has short circuit protection. When the output is shorted to ground, the oscillator The EN pin provides electrical on/off control of the regulator. Once the EN pin voltage exceeds Under Voltage Lockout The CAT7105 incorporates an under voltage lockout circuit to keep the device disable when VIN is below the UVLO start threshold. During power up, internal circuit are held inactive until VIN exceeds the UVLO start threshold voltage. Once the VULO start threshold voltage is frequency is reduced to prevent the inductor current from increasing beyond the N MOS current limit. The NMOS current limit is also reduced to lower the short circuit current. The frequency and current limit will return to the reached, device start-up begins. The device operates until VIN fall below the UVLO stop threshold voltage. The typical hysteretic in the UVLO comparator is 200mV. normal values once the short circuit condition is removed and the feedback voltage reaches 1.23V. Boost Capacitor The CAT logo is a registered trademark of Chip Advanced Technology 2007 Chip Advanced Technology Inc. – All Right Reserved. Connect a 0.01µF low ESR ceramic capacitor between the BS pin and SW pin. This capacitor May-2007 Rev:0.94 6/12 CAT7105 provides the gate drive voltage for the high side MOSFET. Thermal Shutdown The CAT7105 protects itself from overheating with an internal thermal shutdown circuit. If the junction temperature exceeds the thermal shutdown threshold, the voltage reference is grounded and high side MOSFET is turned off. Compensation The system stability is controlled through COMP pin. It will present a general design procedure to help insure a stable and operational circuit. The design in this data sheet is optimized for particular requirements. If different conversions are requires, some of the components may need to be changed to ensure stability. The power components and their effects will be determined first, and then the compensation components will be chosen to produce stability. Output Voltage The output voltage is set using the FB pin and a resistor divider connected to the output as shown in Figure1. The FB pin voltage is 1.23V, so the ratio of the feedback resistors sets the output voltage according to the following equation: VFB = VOUT * R2 / (R1 + R2) Thus the output voltage is: VOUT = 1.23 * (R1 + R2) / R2 The CAT logo is a registered trademark of Chip Advanced Technology 2007 Chip Advanced Technology Inc. – All Right Reserved. May-2007 Rev:0.94 7/12 CAT7105 Package Dimensions The CAT logo is a registered trademark of Chip Advanced Technology 2007 Chip Advanced Technology Inc. – All Right Reserved. May-2007 Rev:0.94 8/12 CAT7105 Classification Reflow Profiles Reflow Profile Average Ramp-Up Rate (Tsmax to Tp) Preheat -Temperature Min(Tsmin) -Temperature Max(Tsmax) -Time(tsmin to ts tsmax) Time maintained above: -Temperature(TL) -Time(tL) Peak Temperature(Tp) Time within 5 ℃ of actual Peak Temperature(tp) Ramp-Down Rate Time 25℃ to Peak Temperature Green Assembly 3℃/second max. 150℃ 200℃ 60-180 seconds 217℃ 60-150 seconds 260 +0/-5 ℃ 20-40 seconds 6℃/second max. 8 minutes max. Note: All Temperature refer to topside of the package, measured on the package body surface. The CAT logo is a registered trademark of Chip Advanced Technology 2007 Chip Advanced Technology Inc. – All Right Reserved. May-2007 Rev:0.94 9/12 CAT7105 Carrier Tape & Reel Dimensions CARRIER TAPE WIDTH C NOMINAL T W TOTAL LENGTH 12mm 9.3±0.1mm 300M 76.2mm The CAT logo is a registered trademark of Chip Advanced Technology 2007 Chip Advanced Technology Inc. – All Right Reserved. 0.06±0.01mm May-2007 Rev:0.94 10/12 CAT7105 The CAT logo is a registered trademark of Chip Advanced Technology 2007 Chip Advanced Technology Inc. – All Right Reserved. May-2007 Rev:0.94 11/12 CAT7105 HEADQUARTERS: 3F, No.1, Jin-Shan 8th St., Hsin-Chu City 300, Taiwan (R.O.C.) Tel: +886-3-666-8301 Fax: +886-3-666-8630 Website: http://www.chipadvanced.com TAIPEI OFFICE: 4F, No.112, Jhouzih St., Neihu District, Taipei City 114, Taiwan (R.O.C.) Tel: +886-2-87516119 Fax: +886-2-87516359 Information furnished is believed to be accurate and reliable. However, CAT Inc. assumes no responsibility for the consequences for use of such information nor for any infringement 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 CAT Inc. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information if previously supplied. CAT Inc. products are not authorized for use as critical components in life support devices or systems without the express written approval of CAT Inc. The CAT logo is a registered trademark of Chip Advanced Technology 2007 Chip Advanced Technology Inc. – All Right Reserved. May-2007 Rev:0.94 12/12