UNISONIC TECHNOLOGIES CO., LTD UD38252 CMOS IC 38V SYNCHRONOUS BUCK CONVERTER WITH CC/CV DESCRIPTION UTC UD38252 is a wide input voltage, high efficiency Active CC step-down DC/DC converter that operates in either CV (Constant Output Voltage) mode or CC (Constant Output Current) mode. UTC UD38252 provides up to 2.5A output current at 160kHz switching frequency. Current mode control provides fast transient response and cycle-by-cycle current limit. An internal soft-start prevents inrush current at turn-on, provides a very compact solution with minimal external components. HSOP-8 FEATURES * Wide 8V to 38V Operating Input Range * Integrated 140mΩ Power MOSFET Switches * Output Adjustable from VFB(1.00V±2%) to 5.5V * Up to 92% Efficiency * Internal Soft-Start. * Stable with Low ESR Ceramic Output Capacitors * Fixed 160KHz Frequency * Cycle-by-Cycle Over Current Protection * Input Under/Over Voltage Lockout ORDERING INFORMATION Ordering Number UD38252G-SH2-R Package HSOP-8 Packing Tape Reel UD38252G-SH2-R (1)Packing Type (1) R: Tape Reel (2)Package Type (2) SH2: HSOP-8 (3)Green Package (3) G: Halogen Free and Lead Free MARKING www.unisonic.com.tw Copyright © 2015 Unisonic Technologies Co., Ltd 1 of 7 QW-R115-008.A UD38252 CMOS IC PIN CONFIGURATION BS 1 8 SEN2 IN 2 7 SEN1 GND SW 3 6 COMP 5 GND 4 PIN DESCRIPTION PIN NO. PIN NAME 1 BS 2 IN 3 SW 4 GND PAD 5 FB 6 COMP 7 8 SEN1 SEN2 FB DESCRIPTION Boot-Strap Pin. Supply high side gate driver. Decouple this pin to LX pin with 24ohm + 0.1uF ceramic cap. Power Input pin. Bypass IN to GND with a suitably large capacitor to eliminate noise on the input to the IC. Power Switching Output. SW is the switching node that supplies power to the output. Connect the output LC filter from SW to the output load. Ground. Ground (Connect to GND). Feedback Input. FB senses the output voltage to regulate that voltage. Drive FB with a resistive voltage divider from the output voltage. Compensation Node. COMP is used to compensate the regulation control loop. Connect a series RC network from COMP to GND to compensate the regulation control loop. The Current Sense Input (-) pin. The Current Sense Input (+) pin = VOUT. BLOCK DIAGRAM IN Internal Power CURRENT SENSE AMPLIFIER Input UVLO 7.0V VDD BS SEN+ M1 SEN1.1V FB PWM Control & Protect Logic SW 1V M2 COMP Softstart Thermal Protection UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw GND 2 of 7 QW-R115-008.A UD38252 CMOS IC ABSOLUTE MAXIMUM RATING (TA=25°C, unless otherwise specified) PARAMETER SYMBOL RATINGS UNIT Supply Voltage VIN -0.3 ~ +42 V Switch Node Voltage VSW -0.3 ~ VIN+0.3 V Boost Voltage VBS VSW-0.3 ~ VSW+ 6 V All Other Pins Voltage -0.3 ~ +6 V Lead Temperature TL 260 °C Junction Temperature TJ 150 °C Storage Temperature TSTG -65 ~ +150 °C Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. RECOMMENDED OPERATING CONDITIONS PARAMETER Input Supply Voltage Output Voltage Ambient Temperature SYMBOL VIN VOUT TA RATINGS 8 ~ 38 VFB ~ 6 -40 ~ +85 UNIT V V °C THERMAL CHARACTERISTICS PARAMETER SYMBOL RATINGS Junction To Ambient θJA 40 Junction to Case θJC 15 Note: θJA is measured with the PCB copper area of approximately 1 in2(Multi-layer). That need connect to pad. UNIT °C/W °C/W exposed ELECTRICAL CHARACTERISTICS (VIN=12V, TA=25°C, unless otherwise specified) PARAMETER Input Voltage Range Quiescent Current Feedback Voltage Feedback Overvoltage Threshold High-Side Switch On Resistance (Note) Low-Side Switch On Resistance (Note) High-Side Switch Leakage Current Upper Switch Current Limit Lower Switch Current Limit Oscillation Frequency Short Circuit Oscillation Frequency Maximum Duty Cycle Minimum On Time (Note1) Sense Voltage VIN OVP Turn-Off Voltage VIN OVP Hysteresis Input Under Voltage Lockout Threshold Input Under Voltage Lockout Threshold Hysteresis Soft-Start Period Thermal Shutdown Thermal Shutdown Hysterisis Note: Guaranteed by design. SYMBOL TEST CONDITIONS VIN ICCQ VFB=1.05V VFB 8V≤VIN≤38V OVP(FB) RDS(ON)1 RDS(ON)2 VFB=1.05V, VSW=0V Minimum Duty Cycle From Drain to Source FOSC1 FOSC2 VFB=<0.5V DMAX TON(min) △VSEN (VSEN2)-(VSEN1) Input voltage rising Input voltage falling UVLO VIN Rising 0.98 TYP 1 1.00 1.1X 150 140 MAX 38 1.5 1.02 10 2.9 114 6.5 3.5 0.9 160 60 90 220 120 40 5 7.0 126 7.5 UNIT V mA V VFB mΩ mΩ μA A A KHz KHz % ns mV V V V UVLO-Hys 800 mV TSD TSH 3 150 30 ms °C °C UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw MIN 8 3 of 7 QW-R115-008.A UD38252 CMOS IC FUNCTION DESCRIPTIONS The UTC UD38252 is a synchronous rectified, current-mode, step-down regulator. It regulates input voltages from 8V to 38V down to an output voltage as low as VFB, and supplies up to 2.5A of load current. The UTC UD38252 uses current-mode control to regulate the output voltage. The output voltage is measured at FB through a resistive voltage divider and amplified through the internal Tran conductance error amplifier. The converter uses internal N-Channel MOSFET switches to step-down the input voltage to the regulated output voltage. Since the high side MOSFET requires a gate voltage greater than the input voltage, a boost capacitor connected between SW and BS is needed to drive the high side gate. The boost capacitor is charged from the internal 5V rail when SW is low. When the UTC UD38252 FB pin exceeds 10% of the nominal regulation voltage of VFB, the over voltage comparator is tripped and the COMP pin is discharged to GND, forcing the high-side switch off. APPLICATION INFORMATION Setting the Output Voltage The output voltage is set using a resistive voltage divider from the output voltage to FB pin. The voltage divider divides the output voltage down to the feedback voltage by the ratio. Thus the output voltage is: VOUT VFB R1 R2 R2 For example, VFB =1.00V for a 5.0V output voltage, R2 is 10kΩ, and R1 is 40kΩ. Inductor Selection The inductor is required to supply constant current to the output load while being driven by the switched input voltage. A larger value inductor will result in less ripple current that will result in lower output ripple voltage. However, the larger value inductor will have a larger physical size, higher series resistance, and/or lower saturation current. A good rule for determining the inductance to use is to allow the peak-to-peak ripple current in the inductor to be approximately 30% of the maximum switch current limit. VIN <28V <35V Inductor 33uH 22uH The choice of which style inductor to use mainly depends on the price vs. size requirements and any EMI requirements. CC Measurement (L=33uH) RSEN 100mΩ IOUT 900mA 50mΩ 2000mA UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 40mΩ 2500mA 37mΩ 2700mA 4 of 7 QW-R115-008.A UD38252 CMOS IC TYPICAL APPLICATION CIRCUIT L1 33μH Input 8~38V C7 100μF 50V C1 2.2μF 40V D1 SK34 C5 100μF IN SW BS UTC COMP UD38252 C3 3.3nF PAD VOUT 5V 2.4A 37mΩ R5 24Ω C6 0.1μF RSEN R1 C2 40kΩ 10μF 10V C8 470μF 10V SEN1 SEN2 GND R2 10kΩ FB R3 15kΩ VOUT=VFB × (1+R1/R2), VFB = 1.00V, R2 suggest 1K~30KΩ ISEN = 2.7A (ISEN≒VSEN(0.1V) / RSEN(37mΩ)) UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 5 of 7 QW-R115-008.A UD38252 CMOS IC TYPICAL CHARACTERISTICS Quiescent Current vs. Input Voltage Quiescent Current, ICCQ (mA) Quiescent Current, ICCQ (mA) Efficiency, EFF (%) Efficiency Test (VOUT=5V) 100 90 80 70 60 50 40 30 20 10 0 12VIN 24VIN 0 2.0 1.2 1.0 0.8 0.6 0.4 0.2 0 0 10 20 30 Input Voltage, VIN (A) 40 Power On VIN=12V, VOUT=5V, IOUT=0A Frequency vs. Input Voltage 175 173 171 169 167 165 163 161 159 157 155 0.5 1.0 1.5 Output Current, IOUT (A) 2.0 1.8 1.6 1.4 VIN SW VOUT IOUT 0 10 20 30 Input Voltage, VIN (A) 40 Power On VIN=12V, VOUT=5V, ILOAD=2A Power On VIN=24V, VOUT=5V, ILOAD=2A VIN VIN SW SW VOUT IOUT VOUT IOUT UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 6 of 7 QW-R115-008.A UD38252 CMOS IC TYPICAL CHARACTERISTICS (Cont.) UTC assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all UTC products described or contained herein. UTC products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. UNISONIC TECHNOLOGIES CO., LTD www.unisonic.com.tw 7 of 7 QW-R115-008.A