FR9702 fitipower integrated technology lnc. 23V, 1.8A, 1.4MHz Asynchronous Step-Down DC/DC Converter Description Features The FR9702 is a monolithic step-down switch mode converter with a built-in power MOSFET. It achieves 1.8A output current over a wide input supply range with excellent load and line regulation. Current mode operation provides fast transient response and eases loop stabilization. Fault condition protection includes cycle-by-cycle current limiting and over temperature protection. The FR9702 requires a minimum number of available standard external components. The FR9702 is available in TSOT23-6 and SOT23-6 packages. z z z z z z z z z z z z Pin Assignment TOP VIEW BS 1 6 SW GND 2 5 VIN FB 3 4 EN 1.8A Output Current 180mΩ Internal Power MOSFET Switch Stable with Low ESR Output Ceramic Capacitors Up to 92% Efficiency Fixed 1.4MHz Frequency Current Mode Operation Over-Temperature Protection with Hiccup-Mode Cycle-by-Cycle Over Current Protection Wide 4.5V to 23V Operating Input Range Output Adjustable from 0.805V to 15V 10uA Shutdown Current Available in TSOT23-6 and SOT23-6 Packages Applications z z z z z Distributed Power Systems Battery Charger OLPC, Netbook Pre-Regulator for Linear Regulators WLED Drivers Ordering Information FR9702□□□ TR: Tape / Reel G: Green Package Type S6: SOT-23-6 FR9702-1.0-DEC-2009 1 FR9702 fitipower integrated technology lnc. Absolute Maximum Ratings (Note 1) Supply Voltage VIN.....................................................................................26V VSW...................................................................................–0.3V to VIN + 0.3V VBS………………………………………………………………………...Vsw + 6V All Other Pins………………………………………………………...–0.3V to +6V Junction Temperature……………………………………………………….150°C Lead Temperature .................................................................................260°C Storage Temperature ...........................................................–65°C to +150°C Recommended Operating Conditions (Note 2) Input Supply Voltage VIN………………………………………………4.5V ~ 23V Output Voltage VOUT.................................................................0.805V ~ 15V Ambient Temperature TA……………………………………………-40°C ~ 85°C Thermal Characteristics TSOT23-6 θJA…………………………………………….………………220°C /W TSOT23-6 θJC……………………………..………………….………..…110°C /W SOT23-6 θJA……………………………………………………………...220°C /W SOT23-6 θJC………………………………………………………………110°C /W Note 1: Stresses exceed those ratings may damage the device. Note 2: If out of its operation conditions, the device is not guaranteed to function. Electrical Characteristic ( VIN = 12V, TA = 25℃, unless otherwise specified ) Parameter Test Conditions Min Typ Max Unit Feedback Voltage Switch-On Resistance (*) Switch Leakage Current Limit (*) Oscillator Frequency Fold-back Frequency Maximum Duty Cycle Minimum On-Time (*) 4.5V ≤ VIN ≤ 23V 0.785 0.805 180 0.825 V mΩ μA A MHz KHz % ns FR9702-1.0-DEC-2009 VEN = 0V, VSW = 0V 10 1.2 VFB = 0V 3 1.4 460 85 100 1.7 2 FR9702 fitipower integrated technology lnc. Electrical Characteristic (continued) ( VIN = 12V, TA = 25℃, unless otherwise specified ) Test Conditions Parameter Under Voltage Lockout Threshold Rising Under Voltage Lockout Threshold Hysteresis EN Input Low Voltage EN Input High Voltage Min Typ Max Unit 4.1 4.4 4.7 V 250 mV 0.4 V V 1.2 Supply Current (Shutdown) VEN = 2V VEN = 0V VEN = 0V 2.0 0.1 10 μA Supply Current (Quiescent) VEN = 2V, VFB = 1V 1.8 mA 150 °C EN Input Current Over-Temperature Protection Threshold (*) μA *: Guaranteed by design Block Diagram + OVP Oscillator + 460KHz / 1.4MHz - BS Error Amplifier S SET Q Driver R CLR High-Side MOSFET SW Q Current Comparator + Ccomp REGULATOR - 1.2V CLK + EN 6V - 0.805V + + 0.45V VIN - - FB Current Sense Amplifier + 0.9V Internal Compensation Rcomp RC GND OVP OTP VIN UVLO 950K Figure 1 FR9702-1.0-DEC-2009 FR9702 Functional Block Diagram 3 FR9702 fitipower integrated technology lnc. Function Pin Description Pin NO. Pin Name Pin Description Bootstrap. A 22nF capacitor is connected between SW and BS pins to drive the power switch’s gate above the supply voltage. Ground. This pin is the voltage reference for the regulated output voltage. For this reason care must be taken in its layout. Feedback. An external resistor divider from the output to GND, tapped to the FB pin sets the output voltage. 1 BS 2 GND 3 FB 4 EN On/Off Control Input. Pull EN above 1.2V and below 5V to turn the device on. 5 VIN Power Supply Input. Drive 4.5V to 23V voltage to this pin to power on this chip. Connecting a 10uF ceramic bypass capacitor between VIN and GND to eliminate noise. 6 SW Switch Output. Connect this pin to the switching end of the inductor. Typical Application Circuit FR9702 Figure 2 FR9702-1.0-DEC-2009 Output 3.3V Application Circuit 4 FR9702 fitipower integrated technology lnc. Typical Operating Characteristics VIN = 12V, VOUT = 3.3V, C1 = 10uF, C2 = 22uF, L1 = 4.7uH, TA = +25℃, unless otherwise noted. Efficiency vs. Loading Efficiency vs. Loading 100% 100% 90% 90% 80% 80% VIN =12V VIN =5V 60% 50% 40% 30% VIN =23V VIN =12V 70% VIN =23V Efficiency Efficiency 70% 60% 50% 40% 30% 20% 20% VOUT = 3.3V 10% VOUT = 5V 10% 0% 0% 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0 0.2 0.4 0.6 0.8 Load current (A) 1 1.2 1.4 1.6 1.8 Load current (A) Feedback Voltage vs. Case Temperature Switching Frequency vs. Case Temperature IOUT = 0.2A IOUT = 0.2A 0.816 1.6 0.814 1.55 Switching Frequency (MHz) Feedback Voltage (V) 0.812 0.81 0.808 0.806 0.804 0.802 1.5 1.45 1.4 1.35 1.3 0.8 1.25 0.798 1.2 0.796 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 -40 100 -30 -20 -10 DC Ripple Waveform IOUT = 1.8A VIN 50mV/div. VIN 100mV/div. VOUT 10mV/div. VOUT 10mV/div. IL 0.5A/div. IL 0.5A/div. VSW 5V/div. VSW 5V/div. 400ns/div. FR9702-1.0-DEC-2009 10 20 30 40 50 60 70 80 90 100 Case Temperature (℃) Case Temperature (℃) IOUT = 0.2A 0 DC Ripple Waveform 400ns/div. 5 FR9702 fitipower integrated technology lnc. Typical Operating Characteristics (continued) VIN = 12V, VOUT = 3.3V, C1 = 10uF, C2 = 22uF, L1 = 4.7uH, TA = +25℃, unless otherwise noted. Startup Through Enable Waveform Startup Through Enable Waveform IOUT = 0.2A IOUT = 1.8A VEN 5V/div. VEN 5V/div. VOUT 1V/div. IL 1A/div. VOUT 1V/div. IL 1A/div. VSW 5V/div. VSW 5V/div. 40us/div. 40us/div. Shutdown Through Enable Waveform Shutdown Through Enable Waveform IOUT = 0.2A IOUT = 1.8A VEN 5V/div. VEN 5V/div. VOUT 1V/div. VOUT 1V/div. IL 1A/div. IL 1A/div. VSW 5V/div. VSW 5V/div. 40us/div. 200us/div. Load Transient Waveform Short Circuit Test Waveform IOUT = 200mA to 1.8A step VOUT 1V/div. VOUT 100mV/div. IL 1A/div. IL 1A/div. 400us/div. FR9702-1.0-DEC-2009 20us/div. 6 FR9702 fitipower integrated technology lnc. Application Information Setting EN Automatic Startup Voltage FR9702 The external resistor divider is used to set the EN automatic startup voltage: R4 = VEN ⎛ VIN-VEN ⎞ ⎜ R3 ⎟ ⎝ ⎠ 5V ≈ 71.5KΩ ⎛ 12V-5V ⎞ ⎜ 100KΩ ⎟ ⎝ ⎠ Table 1 shows a list of resistor selection for common input voltages: Table 1—Resistor Selection for Common Input Voltages VIN R3 R4 5V 100KΩ NC 12V 100KΩ 71.5KΩ 16V 100KΩ 45.3KΩ Setting Output Voltage The external resistor divider is used to set the output voltage. FR9702 feedback resistors are unconcerned of compensation and provide an easy way to program output voltage. Table 2 shows a list of resistor selection for common output voltages: ⎛ ⎝ VOUT = 0.805 × ⎜1+ FR9702-1.0-DEC-2009 R1 ⎞ ⎟ V R2 ⎠ VOUT R1 R2 5V 43KΩ 8.2KΩ 3.3V 30.9KΩ 10KΩ 2.5V 21KΩ 10KΩ 1.8V 12.4KΩ 10KΩ 1.2V 4.99KΩ 10KΩ Selecting the Inductor For example, VIN = 12V, R3 = 100KΩ, thus R4 resistor value is: R4 = Table 2—Resistor Selection for Common Output Voltages A 4.7μH inductor with a DC current rating of at least 25% percent higher than the maximum load current is recommended for most applications. For highest efficiency, the inductor’s DC resistance should be less than 200mΩ. For most designs, the required inductance value can be derived from the following equation. ΔI=0.3 × IL(MAX) VOUT ⎛ ⎞ L ≥ ( VIN-VOUT ) × ⎜ ⎟ ⎝ FSW × ΔI × VIN ⎠ Where ΔI is the inductor ripple current. Choose the inductor ripple current to be 30% of the maximum load current. The maximum inductor peak current is calculated from: IL(MAX) = ILOAD + ΔIL 2 Under light load conditions below 100mA, a larger inductance is recommended for improved efficiency. Selecting the Input Capacitor The input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. The input capacitor impedance at the switching frequency should be less than the input source impedance to prevent 7 FR9702 fitipower integrated technology lnc. recommended to follow these general guidelines high frequency switching current from passing through the input. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most applications, a 10μF capacitor is sufficient. show below: 1. Place the input capacitors, output capacitors as close to the device as possible. Trace to these capacitors should be as short and wide as possible to minimize parasitic inductance Selecting the Output Capacitor and resistance. The output capacitor keeps the output voltage ripple small and a 22uF ceramic capacitor with X5R or X7R dielectrics is recommended for its low ESR characteristics. 2. Place VIN bypass capacitors close to the VIN pin. 3. Place feedback resistors close to the FB pin. 4. Keep the sensitive signal FB away from the switching signal SW. External Bootstrap Diode An external bootstrap diode is recommended if the input voltage is less than 5V or if there is a 5V system rail available. This diode helps improve the efficiency. Low cost diodes, such as 1N4148 are suitable for this application. FR9702 Figure 3 Recommended Layout Diagram Rectifier Diode Use a Schottky diode as the rectifier to conduct current when the high-side power MOSFET is off. The Schottky diode must have current rating higher than the maximum output current and the reverse voltage rating higher than the maximum input voltage. PCB Layout Recommendation The device’s performance and stability is dramatically affected by PCB layout. It is FR9702-1.0-DEC-2009 8 FR9702 fitipower integrated technology lnc. Package Information SOT23-6 D 5 4 1 2 3 R c L2 e e1 ( TOP VIEW ) GAUGE PLANE L E E1 L1 θ 6 ( FRONT VIEW ) A A2 θ2 UNIT: MM y A1 b 4×θ1 ( SIDE VIEW ) 1.2 2.6 0.6 0.95 ( PCB FOOTPRINT ) SYMBOLS A A1 A2 b c D E E1 e e1 L L1 L2 y R θ θ1 θ2 MIN 1.05 0.05 1.00 0.30 0.08 2.80 2.60 1.50 NOM ------1.10 ------2.90 2.80 1.60 0.95 BSC 1.90 BSC 0.35 0.45 0.60 REF 0.25 BSC ------0.10 ---0˚ ---7˚ NOM 5˚ NOM MAX 1.35 0.15 1.20 0.50 0.20 3.00 3.00 1.70 0.55 0.10 ---8˚ NOTES: 1. JEDEC OUTLINE: MO-178C 2. DIMENSION “D” DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED .10mm PER SIDE. 3. DIMENSION “E1” DOES NOT INCLUDE INTER-LEAD FLASH, OR PROTRUSIONS. INTER-LEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED .15mm PER SIDE FR9702-1.0-DEC-2009 9 FR9702 fitipower integrated technology lnc. Carrier Tape & Reel Dimensions SOT23-6 9.20±0.10 76.2(3.0 INCHES)NOMINAL INSIDE CORE DIAMETER 0.048±0.005 HEAT SEALABLE ADHESIVE THIS SIDE Φ1.5+0.1/-0.0 4.00 Φ1.00 MIN 2.00±.05 4.00 0.25±.05 1.75 ± .10 B B A 3.50 ± .05 R 0.3 MAX Bo 8.0 +0.3/-0.1 A R 0.3 TYP Ko Ao SECTION A - A SECTION B - B 0.20 MAX. Ao = 3.15 NOTES: Bo = 3.20 Ko = 1.40 +0.10/-0 1. DIM IN MM. 2. 10 SPROCKET HOLE PITCH CUMULATIVE TOLERANCE ±0.2. 3. POCKET POSITION RELATIVE TO SPROCKET HOLE MEASURED AS TRUE POSITION OF POCKET, NOT POCKET HOLE. Life Support Policy Fitipower’s products are not authorized for use as critical components in life support devices or other medical systems. FR9702-1.0-DEC-2009 10