LC2632CS8TR

LC2632 28V, 2A, 500KHz Synchronous Step-Down DC/DC Converter DESCRIPTION FEATURES The LC2632 is a fully integrated, synchronous rectified step-down converter that provides wide 4.2V to 28V input voltage range and 2A continuous load current capability. The LC2632 can operate at PFM mode to achieve high efficiency and reduce power loss at light load. In shutdown mode, the Max supply current is about 3μA.     The LC2632 protection function includes cycle-bycycle current limit, UVLO and thermal shutdown. Besides, internal soft-start prevents inrush current at fast power-on. This device uses slope compensated current mode control which provides fast load transient response. Internal loop compensation function reduces the external compensator components and simplifies the design process. The LC2632 requires a minimum number of readily available standard external components and is available in ESOP-8 (Exposed Pad) package and provides good thermal conductance. PIN OUT & MARKING BST SW GND APPLICATIONS     Distributed power system Flat panel television and monitors STB (set-top-box) Networking, XDSL modem ORDERING INFORMATION PART No. PACKAGE Tape&Reel NC GW LLDYW VIN           Wide input voltage range: 4.2V to 28V 2A output current 0.8V reference voltage Low RDS(ON) integrated power MOSFET (180/110mΩ) 3μA(Max) shutdown current Integrated internal compensation High efficiency at light load Internal 1ms soft-start Cycle-by-cycle current limit Over-temperature protection with auto recovery Under voltage lockout(UVLO) Hiccup short circuit protection Available in ESOP8 exposed pad package RoHS compliant EN LC2632CS8TR ESOP-8 2500/Reel NC FB ESOP8 GW: Product Code LL: Lot No. D: Fab code YW: Date code www.leadchip.com.cn 1 Your final power solution LC2632 TYPICAL APPLICATION CIN &COUT use ceramic capacitors application circuit CIN &COUT use electrolytic capacitors application circuit Note: If the input voltage is below 12V, R1 can be set to 0K and R2 can be removed. Table1. recommended component values VIN=24V, the recommended BOM list is shows as below. VOUT 5V 3.3V 2.8V 2.5V 1.8 1.2V 5V 3.3V 2.8V 2.5V 1.8 1.2V C1 C2 10uF/MLCC 10uF/MLCC 100uF/35V/ECL 0.1uF/MLCC www.leadchip.com.cn L R3 R4 3.3uH-6.8uH 2.2uH-4.7uH 2.2uH-4.7uH 2.2uH-4.7uH 2.2uH-4.7uH 2.2uH-3.3uH 3.3uH-6.8uH 2.2uH-4.7uH 2.2uH-4.7uH 2.2uH-4.7uH 2.2uH-3.3uH 2.2uH-3.3uH 68K 47K 30K 39K 15K 7.5K 68K 47K 30K 39K 15K 7.5K 13K 15K 12K 18K 12K 15K 13K 15K 12K 18K 12K 15K 2 C5 22uF/MLCC 220uF/6.3V/ECL Your final power solution LC2632 ABSOLUTE MAXIMUM RATING Parameter Value Supply voltage VIN Switch node voltage VSW Boost voltage VBST Enable voltage VEN The others pins Operating temperature range Storage temperature range Lead temperature (soldering, 10s) -0.3V to 30V -0.3V to (VIN+0.5V) VSW-0.3V to VSW+5V -0.3V to 12V -0.3V to 6V -40C to 85C -65C to 150C 300C Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability. RECOMMENDED WORK CONDITIONS Item Min Supply voltage VIN Ambient temperature Recommended Max. Unit 28 85 V C 4.2 -40 ELECTRICAL CHARACTERISTICS (VIN =12V, TA=25C, unless otherwise stated) Parameter Conditions Input voltage range UVLO threshold UVLO hysteresis Supply current in operation Supply current in shutdown Regulated feedback voltage High-side switch on resistance Low-side switch on resistance High-side switch leakage current Upper switch current limit Oscillation frequency Maximum duty cycle Minimum on time EN input voltage “H” EN input voltage “L” Thermal shutdown Min Typ 4.2 Vin rising Vin falling VEN = 5V, VFB = 1V VEN = 0V 3.8V≤VIN ≤28V VBST-SW = 5V VIN = 5V VEN = 0V, VSW = 0V Minimum duty cycle 0.784 3.8 200 150 1 0.8 180 110 0.1 Max Unit 28 V V mV uA uA V mΩ mΩ uA A KHz % ns V V °C 0.816 10 3 500 93 100 1.5 0.6 160 PIN DESCRIPTION PIN # NAME DESCRIPTION 1 2 3 4 5 6 7 8 BST VIN SW GND FB NC EN NC 9 Thermal PAD High side power transistor gate drive boost input. Power input. Bypass with a 22uF ceramic capacitor to GND. Power switching node to connect inductor. Ground. Feedback input with reference voltage set to 0.8V. No connection Enable input. Set this pin to high level to enable the part, low level to disable. No connection Ground. The exposed pad must be soldered to a large PCB area and connected to GND for maximum power dissipation. www.leadchip.com.cn 3 Your final power solution LC2632 ELECTRICAL PERFORMANCE Efficiency vs. Iout Efficiency vs. Iout Vout=3.3V 100% 100% 90% 90% 80% 80% 70% 70% Efficiency(%) Efficiency(%) Vout=1.2V 60% 50% 40% Vin=5V Vin=12V Vin=19V Vin=24V Vin=28V 30% 20% 10% 0% 0.0 0.0 0.1 Iout (A) 1.0 60% 50% 40% Vin=5V Vin=12V Vin=19V Vin=24V Vin=28V 30% 20% 10% 0% 10.0 0.0 Efficiency vs. Iout 0.0 0.1 Iout (A) 1.0 10.0 Vout vs. Iout Vout=5.0V Vout=1.2V 1.22 100% 90% 1.21 80% 60% Vout (V) Efficiency(%) 70% 50% 40% 30% Vin=12V Vin=19V Vin=24V Vin=28V 20% 10% 0% 0.0 0.0 0.1 Iout (A) 1.0 1.20 1.19 Vin=5V Vin=12V Vin=19V Vin=24V Vin=28V 1.18 1.17 0.0 10.0 0.5 Vout vs. Iout 3.34 5.04 3.33 5.03 3.32 5.02 3.31 5.01 Vout (V) Vout (V) 5.05 3.30 3.29 Vin=5V Vin=12V Vin=19V Vin=24V Vin=28V 3.28 3.27 3.26 3.25 1.0 1.5 5.00 4.99 4.98 Vin=12V Vin=19V Vin=24V Vin=28V 4.97 4.96 4.95 2.0 0.0 Iout (A) www.leadchip.com.cn 2.0 Vout=5.0V 3.35 0.5 1.5 Vout vs. Iout Vout=3.3V 0.0 1.0 Iout (A) 0.5 1.0 1.5 2.0 Iout (A) 4 Your final power solution LC2632 Steady State Waveform Steady State Waveform Vin=12V, Vout=3.3V, Cin=Cout=10uF*2, L=4.7uH, Iout=0A Ch1—Vin, Ch2—Vout, Ch3—VSW, Ch4—ISW Vin=12V, Vout=3.3V, Cin=Cout=10uF*2, L=4.7uH, Iout=2A Ch1—Vin, Ch2—Vout, Ch3—VSW, Ch4—ISW Load Transient Load Transient Vin=12V, Vout=3.3V, Iout=0.01~1A Ch2—Vout, Ch4—IL Vin=12V, Vout=3.3V, Iout=1~2A Ch2—Vout, Ch4—IL BLOCK DIAGRAM BST VIN Vref Internal LDO + + - FB VIN - OSC Control Logic EN www.leadchip.com.cn 5 SW GND Your final power solution LC2632 FUNCTIONAL DECRIPTIONS greatly reduces the average short-circuit current to alleviate thermal issues and to protect the regulator. The LC2632 exits hiccup mode once the overcurrent condition is removed. Loop operation The LC2632 is a wide input range, high-efficiency, DC-to-DC step-down switching regulator, capable of delivering up to 2A of output current, integrated with a 180/110mΩ synchronous MOSFET pair, eliminating the need for external diode. It uses a PWM current-mode control scheme. An error amplifier integrates error between the FB signal and the internal reference voltage. The output of the integrator is then compared to the sum of a current-sense signal and the slope compensation ramp. This operation generates a PWM signal that modulates the duty cycle of the power MOSFETs to achieve regulation for output voltage. Light load operation Traditionally, a fixed constant frequency PWM DCDC regulator always switches even when the output load is small. When energy is shuffling back and forth through the power MOSFETs, power is lost due to the finite RDSONs of the MOSFETs and parasitic capacitances. At light load, this loss is prominent and efficiency is therefore very low. LC2632 employs a proprietary control scheme that improves efficiency in this situation by enabling the device into a power save mode during light load, thereby extending the range of high efficiency operation. Internal soft-start The soft-start is important for many applications because it eliminates power-up initialization problems. The controlled voltage ramp of the output also reduces peak inrush current during start-up, minimizing start-up transient events to the input power bus. Startup and shutdown If both VIN and EN are higher than their appropriate thresholds, the chip starts. The reference block starts first, generating stable reference voltage and currents, and then the internal regulator is enabled. The regulator provides stable supply for the remaining circuitries. Three events can shut down the chip: EN low, VIN low and thermal shutdown. In the shutdown procedure, the signaling path is first blocked to avoid any fault triggering. The COMP voltage and the internal supply rail are then pulled down. The floating driver is not subject to this shutdown command. Over-current-protection and hiccup The LC2632 has a cycle-by-cycle over-current limit for when the inductor current peak value exceeds the set current-limit threshold. First, when the output voltage drops until FB falls below the Under-Voltage (UV) threshold (typically 300mV) to trigger a UV event, the LC2632 enters hiccup mode to periodically restart the part. This protection mode is especially useful when the output is dead-shorted to ground. This APPLICATIONS INFORMATION Setting output voltages Selecting the inductor The external resistor divider is used to set the output voltage. The feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor. R2 is then given by: Use a 2.2μH-to-6.8μH inductor with a DC current rating of at least 25% higher than the maximum load current for most applications. For most designs, derive the inductance value from the following equation: Where ΔIL is the inductor ripple current. Choose an inductor current approximately 30% of the maximum load current. The maximum inductor peak current is: www.leadchip.com.cn 6 Your final power solution LC2632 frequency. For simplification, the output ripple can be approximated with: Under light-load conditions (below 100mA), use a larger inductor to improve efficiency. [ ] Selecting the output capacitor The characteristics of the output capacitor also affect the stability of the regulation system. The LC2632 can be optimized for a wide range of capacitance and ESR values. The output capacitor maintains the DC output voltage. Use ceramic, tantalum, or low-ESR electrolytic capacitors. Use low ESR capacitors to limit the output voltage ripple. Estimate the output voltage ripple with: [ ] [ ] Where L is the inductor value and RESR is the equivalent series resistance (ESR) of the output capacitor. For ceramic capacitors, the capacitance dominates the impedance at the switching frequency and causes most of the output voltage ripple. For simplification, estimate the output voltage ripple with: [ Selecting the external boost diode It is recommended to add an external Boost Diode to improve efficiency and stability in these situations when the input voltage is fixed at 5.0V.Any a readily and cheap diode can meet the need of these application such as 1N4148. ] For tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching PCB LAYOUT RECOMMENDATION The device’s performance and stability are dramatically affected by PCB layout. It is recommended to follow these general guidelines shown as below: 1. Place the input capacitors and output capacitors as close to the device as possible. The traces which connect to these capacitors should be as short and wide as possible to minimize parasitic inductance and resistance. 2. Place feedback resistors close to the FB pin. 3. Keep the sensitive signal (FB) away from the switching signal (SW). 4. The exposed pad of the package should be soldered to an equivalent area of metal on the PCB. This area should connect to the GND plane and have multiple via connections to the back of the PCB as well as connections to intermediate PCB www.leadchip.com.cn layers. The GND plane area connecting to the exposed pad should be maximized to improve thermal performance. 5. Multi-layer PCB design is recommended. 7 Your final power solution LC2632 PACKAGE OUTLINE Package ESOP8 Devices per reel 2500 Unit mm Package specification： www.leadchip.com.cn 8 Your final power solution