FR8206S6CTR

深圳市昂宇电子有限公司 Lily 0755-83234073 手机 159 153 736 32 Q Q 100 754 5980 FR8206 fitipower integrated technology lnc. 85T 18V, 3A, 500KHz Synchronous Step-Down DC/DC Converter Description Features The FR8206 is a synchronous step-down DC/DC converter that provides wide 4.5V to 18V input voltage range and 3A continuous load current capability. At light load condition, the FR8206 can operate at PSM mode to support high efficiency and reduce power loss.  Low-Rds(on) Power MOSFET:110mΩ/60mΩ  Internal Compensation Function  Wide Input Voltage Range: 4.5V to 18V  Adjustable Output Voltage Down to 0.8V  3A Output Current  500kHz Switching Frequency  Soft-Start Time 1ms  Cycle-by-Cycle Current Limit  Hiccup Short Circuit Protection  Over-Temperature Protection with Auto Recovery  Input Under Voltage Lockout  SOT-23-6 Package The FR8206 fault protection includes cycle-by-cycle current limit, hiccup short circuit protection, UVLO and thermal shutdown. The Internal soft-start function prevents inrush current at turn-on. This device uses current mode control scheme which provides fast transient response. Internal compensation function reduces external compensatory components and simplifies the design process. In shutdown mode, the supply current is about 1μA. The FR8206 is offered in SOT-23-6 package, which provides good thermal conductance. Applications     STB (Set-Top-Box) LCD Display, TV Distributed Power System Networking, XDSL Modem Pin Assignments Ordering Information S6 Package (SOT-23-6) FR8206□□□ BSTSHDN FB 6 1 TR: Tape/Reel C: Green 4 5 (Marking) 2 GND LX VIN Figure 1. Pin Assignments of FR8206 FR8206-Preliminary 0.1-APR-2014 Package Type S6: SOT-23-6 3 SOT-23-6 Marking Part Number Product Code FR8206S6CTR FC3 1 FR8206 fitipower integrated technology lnc. 85T Typical Application Circuit C3 0.1μF R3 100kΩ 5 6 SHDN 3 VIN 4.5V to 18V BST LX 2 VIN VOUT 1.2V R1 4.99kΩ 1% FR8206 C1 10μF/25V CERAMIC L1 2.2μH FB C6 10μF/25V CERAMIC C4 (optional) 4 GND 1 C2 22μF/6.3V CERAMIC x 2 R2 10kΩ 1% Figure 2. CIN /COUT use Ceramic Capacitors Application Circuit C3 0.1μF R3 100kΩ 5 6 SHDN 3 VIN 4.5V to 18V BST LX VIN 2 FR8206 C1 100μF/25V EC FB C6 0.1μF 4 GND 1 L1 2.2μH VOUT 1.2V R1 4.99kΩ 1% C4 (optional) C2 100μF/6.3V EC R2 10kΩ 1% Figure 3. CIN /COUT use Electrolytic Capacitors Application Circuit VIN=12V, the recommended BOM list is as below. VOUT C1 R1 R2 C6 C4 L1 C2 1.2V 10μF MLCC 4.99kΩ 10kΩ 10μF MLCC 10pF~1nF 2.2μH 22μF MLCC x2 1.8V 10μF MLCC 4.99kΩ 3.92kΩ 10μF MLCC 10pF~1nF 3.3μH 22μF MLCC x2 2.5V 10μF MLCC 4.99kΩ 2.32kΩ 10μF MLCC 10pF~1nF 3.3μH 22μF MLCC x2 3.3V 10μF MLCC 30.9kΩ 9.76kΩ 10μF MLCC 10pF~1nF 4.7μH 22μF MLCC x2 5V 10μF MLCC 30.9kΩ 5.76kΩ 10μF MLCC 10pF~1nF 4.7μH 22μF MLCC x2 1.2V 100μF EC 4.99kΩ 10kΩ 0.1μF -- 2.2μH 100μF EC 1.8V 100μF EC 4.99kΩ 3.92kΩ 0.1μF -- 3.3μH 100μF EC 2.5V 100μF EC 4.99kΩ 2.32kΩ 0.1μF -- 3.3μH 100μF EC 3.3V 100μF EC 30.9kΩ 9.76kΩ 0.1μF -- 4.7μH 100μF EC 5V 100μF EC 30.9kΩ 5.76kΩ 0.1μF -- 4.7μH 100μF EC Table 1. Recommended Component Values FR8206-Preliminary 0.1-APR-2014 2 FR8206 fitipower integrated technology lnc. 85T Functional Pin Description Pin Name Pin No. GND 1 Ground Pin. LX 2 Power Switching Node. LX is the output of the internal high side NMOS switch. VIN 3 Power Supply Input Pin. FB 4 Voltage Feedback Input Pin. Connect FB and VOUT with a resistive voltage divider. This IC senses feedback voltage via FB and regulates it at 0.8V. 5 Enable Input Pin. Pull high to turn on IC, and pull low to turn off IC. self-startup. 6 High Side Gate Drive Boost Pin. A capacitor rating between 10nF~100nF must be connected from this pin to LX. It can boost the gate drive to fully turn on the internal high side NMOS. BST Pin Function Drive VIN pin by 4.5V to 18V voltage to power on the chip. Connect VIN with a 100kΩ resistor for Block Diagram VIN UVLO & POR SHDN ISEN Internal Regulator OTP VCC VCC Oscillator BST High-Side MOSFET S FB Soft Start Current Comp R OTP PWM Control Driver Logic LX UVLO Low-Side MOSFET Vref Current Limit GND Figure 4. Block Diagram of FR8206 FR8206-Preliminary 0.1-APR-2014 3 fitipower integrated technology lnc. FR8206 85T Absolute Maximum Ratings (Note1) ● Supply Voltage VIN ------------------------------------------------------------------------------------------- -0.3V to +20V ● Enable Voltage H ------------------------------------------------------------------------------------- -0.3V to +20V ● LX Voltage VLX ------------------------------------------------------------------------------------------------ -0.3V to VIN+0.3V ● Dynamic LX Voltage in 15ns Duration------------------------------------------------------------------- -5V to VIN+5V ● BST Pin Voltage VBST --------------------------------------------------------------------------------------- -0.3V to VLX+6.5V ● All Other Pins Voltage -------------------------------------------------------------------------------------- -0.3V to +6V ● Maximum Junction Temperature (TJ) ------------------------------------------------------------------- +150°C ● Storage Temperature (TS) --------------------------------------------------------------------------------- -65°C to +150°C ● Lead Temperature (Soldering, 10sec.) ----------------------------------------------------------------- +260°C ● Package Thermal Resistance, (θJA) SOT-23-6 -------------------------------------------------------------------------------------------- +95°C/W ● Package Thermal Resistance, (θJC) SOT-23-6 -------------------------------------------------------------------------------------------- +20°C/W Note 1：Stresses beyond this listed under “Absolute Maximum Ratings" may cause permanent damage to the device. Recommended Operating Conditions ● Supply Voltage VIN ------------------------------------------------------------------------------------------ +4.5V to +18V ● Operation Temperature Range --------------------------------------------------------------------------- -40°C to +85°C FR8206-Preliminary 0.1-APR-2014 4 FR8206 fitipower integrated technology lnc. 85T Electrical Characteristics (VIN=12V, TA=25°C, unless otherwise specified.) Parameter Symbol Conditions Min Typ Max Unit VIN Quiescent Current IDDQ H =2V, VFB=1.0V 1 1.2 mA VIN Shutdown Supply Current ISD H =0V 1 3 μA Feedback Voltage VFB 0.8 0.82 V 4.5V≦VIN≦18V 0.78 High-Side MOSFET RDS(ON) (Note3) RDS(ON) 110 mΩ Low-Side MOSFET RDS(ON) (Note3) RDS(ON) 60 mΩ High-Side MOSFET Leakage Current ILX(leak) High-Side MOSFET Current Limit (Note3) Oscillation Frequency Short Circuit Oscillation Frequency ILIMIT(HS) H =0V, VLX=0V Minimum Duty FOSC FOSC(short) Maximum Duty Cycle DMAX Minimum On Time (Note3) TMIN 10 4.5 400 500 μA A 600 kHz VFB=0V 150 kHz VFB=0.6V 88 % 100 ns 4.3 V Input Supply Voltage UVLO Threshold VUVLO(Vth) Input Supply Voltage UVLO Threshold Hysteresis VUVLO(HYS) 400 mV TSS 1 ms Internal Soft-Start Period H Input Low Voltage H Input High Voltage H Input Current Thermal Shutdown Threshold (Note3) Thermal Shutdown Hysteresis (Note3) H (L H (H H TSD VIN Rising 0.4 2 H =2V V V 2 μA 165 °C 40 °C Note 3：Not production tested. FR8206-Preliminary 0.1-APR-2014 5 FR8206 fitipower integrated technology lnc. 85T Typical Performance Curves VIN=12V, C1=10μFx2, C2=22μFx2, L1=4.7μH, TA=+25°C, unless otherwise noted. VOUT=1.2V VOUT=3.3V 90 80 80 70 70 Efficiency (%) 100 90 Efficiency (%) 100 60 50 40 30 50 40 30 VIN=5V VIN=12V VIN=18V 20 20 10 60 VIN=5V VIN=12V 0 0.01 10 0.1 1 Load Current (A) 0 0.01 10 Figure 5. Efficiency vs. Load Current VIN=12V, IOUT=0.2A 100 0.84 90 0.835 70 Feedback Voltage(V) Efficiency (%) 80 60 50 40 30 20 VIN=12V VIN=18V 0 0.01 0.83 0.825 0.82 0.815 0.81 0.805 0.8 0.1 1 Load Current (A) Figure 7. Efficiency vs. Load Current -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 Temperature (°C) 10 Figure 8. Feedback Voltage vs. Temperature IOUT=3A IOUT=0A VOUT 10 Figure 6. Efficiency vs. Load Current VOUT=5V 10 0.1 1 Load Current (A) 50mV/div. VLX 5V/div. ILX 500mA/div. 1ms/div. Figure 9. Steady State Waveform FR8206-Preliminary 0.1-APR-2014 VOUT 50mV/div. VLX 5V/div. ILX 2.5A/div. 1μs/div. Figure 10. Steady State Waveform 6 FR8206 fitipower integrated technology lnc. 85T Typical Performance Curves (Continued) VIN=12V, VOUT=3.3V, C1=10μFx2, C2=22μFx2, L1=4.7μH, TA=+25°C, unless otherwise noted. IOUT=0A IOUT=3A VIN 10V/div. VIN 10V/div. VOUT 1V/div. VOUT 1V/div. VLX 5V/div. VLX 5V/div. ILX 500mA/div. ILX 2.5A/div. 2ms/div. Figure 11. Power On through VIN Waveform IOUT=0A Figure 12. Power On through VIN Waveform IOUT=3A VIN 5V/div. VOUT 1V/div. VLX 5V/div. ILX 2ms/div. VIN 5V/div. VOUT 1V/div. VLX 5V/div. ILX 2.5A/div. 500mA/div. 20ms/div. 10ms/div. Figure 13. Power Off through VIN Waveform Figure 14. Power Off through VIN Waveform IOUT=0A IOUT=3A VEN 5V/div. VEN 5V/div. VOUT 1V/div. VOUT 1V/div. VLX 10V/div. VLX 10V/div. ILX 500mA/div. ILX 2.5A/div. 400μs/div. 200μs/div. Figure 15. Power On through EN Waveform Figure 16. Power On through EN Waveform FR8206-Preliminary 0.1-APR-2014 7 FR8206 fitipower integrated technology lnc. 85T Typical Performance Curves (Continued) VIN=12V, VOUT=3.3V, C1=10μFx2, C2=22μFx2, L1=4.7μH, TA=+25°C, unless otherwise noted. IOUT=0A IOUT=3A VEN 5V/div. VOUT 1V/div. VLX ILX VEN 5V/div. VOUT 1V/div. 10V/div. VLX 10V/div. 500mA/div. ILX 2.5A/div. 10ms/div. 80μs/div. Figure 17. Power Off through EN Waveform Figure 18. Power Off through EN Waveform IOUT=0A IOUT=0A VIN 5V/div. VOUT 1V/div. VLX 10V/div. ILX 2.5A/div. VIN 5V/div. VOUT 1V/div. VLX 10V/div. ILX 2.5A/div. 4ms/div. 4ms/div. Figure 19. Short Circuit Waveform Figure 20. Short Circuit Recovery IOUT=0.1A to 3A VOUT 500mV/div. ILX 1A/div. 200μs/div. Figure 21. Load Transient Waveform FR8206-Preliminary 0.1-APR-2014 8 fitipower integrated technology lnc. FR8206 85T Function Description The FR8206 is a high efficiency, internal compensation and constant frequency current mode step-down synchronous DC/DC converter. It has integrated high-side (110mΩ, typ) and low-side (60mΩ, typ) power switches, and provides 3A continuous load current. It regulates input voltage from 4.5V to 18V, and down to an output voltage as low as 0.8V. Control Loop Under normal operation, the output voltage is sensed by FB pin through a resistive voltage divider and amplified through the error amplifier. The voltage of error amplifier output is compared to the switch current to control the RS flip-flop. At the beginning of each clock cycle, the high-side NMOS turns on when the oscillator sets the RS flip-flop, and turns off when current comparator resets the RS flip-flop. Then the low-side NMOS will turn on until the clock period ends. Enable The FR8206 H pin provides digital control to turn on/off the regulator. When the voltage of H exceeds the threshold voltage, the regulator will start the soft start function. If the H pin voltage is below the shutdown threshold voltage, the regulator will turn into the shutdown mode and the shutdown current will be smaller than 1μA. For auto start-up operation, connect H to VIN through a 100KΩ resistor. Soft-Start The FR8206 employs internal soft-start functions to reduce input inrush current during start up. Internal soft-start time will be 1ms. Short Circuit Protection The FR8206 provides short circuit protection function to prevent the device damage from short condition. When the short condition occurs and the feedback voltage drops lower than 0.4V, the oscillator frequency will be reduced to 150KHz and hiccup mode will be triggered to prevent the inductor current increasing beyond the current limit. Once the short condition is removed, the frequency will return to normal. Over Current Protection The FR8206 over current protection function is implemented using cycle-by-cycle current limit architecture. The inductor current is monitored by measuring the high-side MOSFET series sense resistor voltage. When the load current increases, the inductor current will also increase. When the peak inductor current reaches the current limit threshold, the output voltage will start to drop. When the over current condition is removed, the output voltage will return to the regulated value. Over Temperature Protection The FR8206 incorporates an over temperature protection circuit to protect itself from overheating. When the junction temperature exceeds the thermal shutdown threshold temperature, the regulator will be shutdown. And the hysteretic of the over temperature protection is 40°C (typ). Internal Compensation Function The stability of the feedback circuit is controlled by internal compensation circuits. This internal compensation function is optimized for most applications and this function can reduce external R, C components. Under Voltage Lockout When the FR8206 is power on, the internal circuits will be held inactive until VIN voltage exceeds the UVLO threshold voltage. And the regulator will be disabled when VIN is below the UVLO threshold voltage. The hysteretic of the UVLO comparator is 400mV (typ). FR8206-Preliminary 0.1-APR-2014 9 FR8206 fitipower integrated technology lnc. 85T Application Information Output Voltage Setting The output voltage VOUT is set by using a resistive divider from the output to FB. The FB pin regulated voltage is 0.8V. Thus the output voltage is: R1 R2 Table 2 lists recommended values of R1 and R2 for most used output voltage. Table 2 Recommended Resistance Values T =0. 1+ VOUT R1 R2 5V 30.9kΩ 5.76kΩ 3.3V 30.9kΩ 9.76kΩ 2.5V 4.99kΩ 2.32kΩ 1.8V 4.99kΩ 3.92kΩ 1.2V 4.99kΩ 10kΩ Place resistors R1 and R2 close to FB pin to prevent stray pickup. A low ESR capacitor is required to keep the noise minimum. Ceramic capacitors are better, but tantalum or low ESR electrolytic capacitors may also suffice. When using tantalum or electrolytic capacitors, a 0.1μF ceramic capacitor should be placed as close to the IC as possible. Output Capacitor Selection The output capacitor is used to keep the DC output voltage and supply the load transient current. When operating in constant current mode, the output ripple is determined by four components: R PPLE t = R PPLE C + t + R PPLE(E L R PPLE E R t + E t t The following figures show the form of the ripple contributions. VRIPPLE(ESR)(t) Input Capacitor Selection The use of the input capacitor is filtering the input voltage ripple and the MOSFETS switching spike voltage. Because the input current to the step-down converter is discontinuous, the input capacitor is required to supply the current to the converter to keep the DC input voltage. The capacitor voltage rating should be 1.25 to 1.5 times greater than the maximum input voltage. The input capacitor ripple current RMS value is calculated as: (RM = (t) + VRIPPLE(C) (t) (t) + VNOISE (t) (t) 1 T T = Where D is the duty cycle of the power MOSFET. This function reaches the maximum value at D=0.5 and the equivalent RMS current is equal to IOUT/2. The following diagram is the graphical representation of above equation. 1.75 3A 1.5 IIN(RMS) (A) + VRIPPLE(ESL) (t) 1.25 = VRIPPLE(t) 2A 1 0.75 1A 0.5 (t) 0.25 0 10 20 30 40 50 60 70 80 90 D (%) FR8206-Preliminary 0.1-APR-2014 10 FR8206 fitipower integrated technology lnc. 85T Application Information (Continued) R PPLE(E R = R PPLE(E L = R PPLE(C = T F C T 1 L E R E L L+E L L= T F C2 That will lower ripple current and result in lower output ripple voltage. The Δ L is inductor peak-to-peak ripple current: L C 1 T F C T T The following diagram is an example to graphically represent Δ L equation. Where FOSC is the switching frequency, L is the inductance value, VIN is the input voltage, ESR is the equivalent series resistance value of the output capacitor, ESL is the equivalent series inductance value of the output capacitor and the COUT is the output capacitor. 1.4 1.2 It is important to use the proper method to eliminate high frequency noise when measuring the output ripple. The figure shows how to locate the probe across the capacitor when measuring output ripple. Remove the scope probe plastic jacket in order to expose the ground at the tip of the probe. It gives a very short connection from the probe ground to the capacitor and eliminates noise. Probe Ground L=4.7μ ΔIL (A) 1 Low ESR capacitors are preferred to use. Ceramic, tantalum or low ESR electrolytic capacitors can be used depending on the output ripple requirements. When using the ceramic capacitors, the ESL component is usually negligible. 0.8 L=6.8μ 0.6 L=10μ 0.4 0.2 5 10 A good compromise value between size and efficiency is to set the peak-to-peak inductor ripple current Δ L equal to 30% of the maximum load current. But setting the peak-to-peak inductor ripple current Δ L between 20%~50% of the maximum load current is also acceptable. Then the inductance can be calculated with the following equation: L =0.3 GND The output inductor is used for storing energy and filtering output ripple current. But the trade-off condition often happens between maximum energy storage and the physical size of the inductor. The first consideration for selecting the output inductor is to make sure that the inductance is large enough to keep the converter in the continuous current mode. T(MA T F T C L To guarantee sufficient output current, peak inductor current must be lower than the FR8206 high-side MOSFET current limit. The peak inductor current is shown as below: PEAK = Load Current Inductor Selection 20 VOUT=3.3V, FOSC=500kHz Ceramic Capacitor FR8206-Preliminary 0.1-APR-2014 15 VIN (V) L= VOUT T 1 L T(MA + L 2 IPEAK IOUT(MAX) ∆IL Time 11 FR8206 fitipower integrated technology lnc. 85T Application Information (Continued) Feedforward Capacitor Selection PCB Layout Recommendation Internal compensation function allows users saving time in design and saving cost by reducing the number of external components. The use of a feedforward capacitor C6 in the feedback network is recommended to improve transient response or higher phase margin. The device’s performance and stability are dramatically affected by PCB layout. It is recommended to follow these general guidelines shown as below: VOUT C4 FB R2 For optimizing the feedforward capacitor, knowing the cross frequency is the first thing. The cross frequency (or the converter bandwidth) can be determined by using a network analyzer. When getting the cross frequency with no feedforward capacitor identified, the value of feedforward capacitor C4 can be calculated with the following equation: C4= 2 1 FCR 1 R1 2. Place feedback resistors close to the FB pin. 3. Keep the sensitive signal (FB) away from the switching signal (LX). 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 layers. The GND plane area connecting to the exposed pad should be maximized to improve thermal performance. 5. Multi-layer PCB design is recommended. 1 1 + R1 R2 Where FCROSS is the cross frequency. To reduce transient ripple, the feedforward capacitor value can be increased to push the cross frequency to higher region. Although this can improve transient response, it also decreases phase margin and causes more ringing. In the other hand, if more phase margin is desired, the feedforward capacitor value can be decreased to push the cross frequency to lower region. In general, the feedforward capacitor range is between 10pF to 1nF. C4 VOUT R1 R2 6 5 4 GND C1 C2 1 C8 2 C6 3 R3 R1 FR8206 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. C3 VIN VOUT L1 LX Figure 22. Recommended PCB Layout Diagram External Diode Selection For 5V input application, it is recommended to add an external bootstrap diode. This helps improving the efficiency. The boost diode can be a low cost one such as 1N4148. D1 1N4148 VIN 5V VIN BST FR8206 C3 LX FR8206-Preliminary 0.1-APR-2014 12 FR8206 fitipower integrated technology lnc. 85T Outline Information SOT-23-6 Package (Unit: mm) SYMBOLS UNIT A DIMENSION IN MILLIMETER MIN MAX 0.90 1.45 A1 0.00 0.15 A2 0.90 1.30 B 0.30 0.50 D 2.80 3.00 E 2.60 3.00 E1 1.50 1.70 e 0.90 1.00 e1 1.80 2.00 L 0.30 0.60 Note：Followed From JEDEC MO-178-C. Carrier Dimensions Life Support Policy Fitipower’s products are not authorized for use as critical components in life support devices or other medical systems. FR8206-Preliminary 0.1-APR-2014 13