FP6397S5

FP6397 High Efficiency 1MHz 2A Synchronous Step Down Converter Description Features The FP6397 is a high efficiency, high frequency synchronous DC-DC step-down converter. The 100% duty cycle feature provides low dropout operation, extending battery life in portable systems.     The internal synchronous switch increases efficiency and eliminates the need for external Schottky diode. At shutdown mode, the input supply current is less than 1µA.           The FP6397 fault protection includes over current protection, short circuit protection, UVLO and thermal shutdown. The Internal soft-start function prevents inrush current at turn-on. The FP6397 is offered in SOT-23-5 and SOT-23-6 Packages. 2.5V~6V Input Voltage Range 0.6V Reference Voltage 2A Output Current Low RDS(ON) for Internal Switch (Top/Bottom): 140/90mΩ 1MHz Switching Frequency Internal Soft-Start Limits the Inrush Current Internal Compensation Function 100% Dropout Operation Power Good Indicator Output (SOT-23-6 Only) Input Over Voltage Protection Over Current Protection Hiccup Short Circuit Protection Over Temperature Protection with Auto Recovery RoHS Compliant and Halogen Free Applications      Pin Assignments Ordering Information FP6397□ S5 Package (SOT-23-5) FB VIN 5 4 1 Set Top Box LCD TV & Tablet AP Router & WiFi Dongle 3.5G & 4G Dongle USB3.0 & SSD storage 2 Package Type S5: SOT-23-5 S6: SOT-23-6 3 EN GND LX S6 Package (SOT-23-6) FB PG VIN 6 5 4 1 2 3 EN GND LX SOT-23-5 Marking Part Number Product Code FP6397S5 FV9 SOT-23-6 Marking Part Number Product Code FP6397S6 FW1 Figure 1. Pin Assignment of FP6397 FP6397-Preliminary 0.3-AUG-2019 1 FP6397 Typical Application Circuit Figure 2. Schematic Diagram VIN=5V, the recommended BOM list is as below. VOUT 3.3V 2.5V 1.8V 1.5V 1.2V 1.05V C1 10μF MLCC 10μF MLCC 10μF MLCC 10μF MLCC 10μF MLCC 10μF MLCC R1 453kΩ 316kΩ 200kΩ 150kΩ 100kΩ 75kΩ R2 100kΩ 100kΩ 100kΩ 100kΩ 100kΩ 100kΩ L1 2.2μH 2.2μH 1.8μH 1.5μH 1.5μH 1.2μH C2 10μF MLCC 10μF MLCC 10μF MLCC 10μF MLCC 10μF MLCC 10μF MLCC Table 1. Recommended Component Values FP6397-Preliminary 0.3-AUG-2019 2 FP6397 Functional Pin Description Pin Name Pin No. (SOT-23-6) Pin No. (SOT-23-5) Pin Function EN 1 1 Enable control pin. Pull high to turn the IC on, and pull low to disable the IC. Don’t leave this pin floating. GND 2 2 Ground pin. LX 3 3 Power switching node. Connect an inductor to the drains of internal high side PMOS and low side NMOS. VIN 4 4 Power supply input pin. Placed input capacitors as close as possible from VIN to GND to avoid noise influence. PG 5 -- Open drain power good output pin. FB 6 5 Voltage feedback input pin. Connect FB and VOUT with a resistive voltage divider. This IC senses feedback voltage via FB and regulates it at 0.6V. Block Diagram PG (SOT-23-6) EN VIN 2M Power Good Enable Control VIN OVP UVLO Slope Compensation 90% VREF FB 1 COMP Control Logic EA VREF Soft Start OSC OTP Driver Logic X LX COMP GND Figure 3. Block Diagram of FP6397 FP6397-Preliminary 0.3-AUG-2019 3 FP6397 Absolute Maximum Ratings (Note 1) ● VIN to GND ------------------------------------------------------------------------------------------------- -0.3V to +6.5V ● LX to GND --------------------------------------------------------------------------------------------------- -0.3V to (VIN +0.3V) ● EN, FB, PG to GND --------------------------------------------------------------------------------------- -0.3V to VIN ● Package Thermal Resistance, (θJA) (Note 2) SOT-23-5 ---------------------------------------------------------------------------------------- 250°C/W SOT-23-6 ---------------------------------------------------------------------------------------- 250°C/W ● Package Thermal Resistance, (θJC) SOT-23-5 ---------------------------------------------------------------------------------------- 130°C/W SOT-23-6 ---------------------------------------------------------------------------------------- 110ºC/W ● Maximum Junction Temperature (T J) ----------------------------------------------------------------- +150°C ● Lead Temperature (Soldering, 10sec.) --------------------------------------------------------------- +260°C ● Storage Temperature (TS) ------------------------------------------------------------------------------- -65°C to +150°C Note 1: Stresses beyond this listed under “Absolute Maximum Ratings" may cause permanent damage to the device. Note 2: θJA is measured at 25°C ambient with the component mounted on a high effective thermal conductivity test board of JEDEC-51-7. The thermal resistance greatly varies with layout, copper thickness, number of layers and PCB size. Recommended Operating Conditions (Note 3) ● Supply Voltage (VIN) ------------------------------------------------------------------------------------------- +2.5V to +6V ● Junction Temperature Range ------------------------------------------------------------------------------- -40°C to +125°C ● Operation Temperature Range (T OPR) -------------------------------------------------------------------- -40°C to +85°C Note 3: The device is not guaranteed to function outside its operating conditions. FP6397-Preliminary 0.3-AUG-2019 4 FP6397 Electrical Characteristics (VIN=5V, TA=25°C, unless otherwise specified.) Parameter Symbol Input Supply Voltage Conditions VIN Input Over Voltage Protection Min 2.5 VIN OVP Shutdown Current ISHDN Quiescent Current Iq Reference Voltage VREF FB Input Leakage Current IFB Typ Max Unit 6.0 V 6.3 EN=GND 0.1 VFB=0.65V, IOUT=0A 40 0.588 VFB=VIN V 1 μA μA 0.6 0.612 V 0.01 1 µA P-Channel MOSFET On-Resistance (Note 4) RDS(ON) 140 mΩ N-Channel MOSFET On-Resistance (Note 4) RDS(ON) 90 mΩ 2.7 A P-Channel Current Limit (Note 4) ILIM 2.2 EN High-Level Input Voltage VEN(H) 1.5 EN Low-Level Input Voltage VEN(L) Under Voltage Lockout Voltage UVLO 2.4 V UVLO Hysteresis VHYS 0.2 V Oscillation Frequency FOSC V 0.4 IOUT=300mA 0.8 Minimum On Time 1.0 50 Maximum Duty Cycle 100 1.2 V MHz ns % PG Rising Threshold VPG (H) VFB Rising 90 % PG Low Threshold VPG (L) VFB falling 85 % PG Sink Current IPG VPG=0.1V 1 mA Internal Soft-Start Time TSS 1 ms 100 Ω 150 °C VOUT Discharge Resistance Thermal Shutdown Temperature (Note 4) TSD Note 4: Guarantee by design. FP6397-Preliminary 0.3-AUG-2019 5 FP6397 Typical Performance Curves VIN=5V, VOUT=1.2V, C1=10μF, C2=10μF, L1=1.5μH, TA=+25°C, unless otherwise noted. VOUT=3.3V 100 100 90 80 70 60 90 80 50 40 30 20 10 0 0.01 Efficiency(%) Efficiency(%) VOUT=1.2V VIN=3.3V 70 60 50 40 30 VIN=4.2V 20 VIN=5.0V 0.1 1 VIN=5.0V 10 0 0.01 10 Load Current (A) -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 10 1.10 1.08 1.06 1.04 1.02 1.00 0.98 0.96 0.94 0.92 0.90 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 Ambient Temperature (℃) Ambient Temperature (℃) Figure 6. Feedback Voltage vs. Temperature IOUT=0A 1 Figure 5. Efficiency vs. Load Current Frequency (MHz) Feedback Voltage (V) Figure 4. Efficiency vs. Load Current 0.65 0.64 0.63 0.62 0.61 0.60 0.59 0.58 0.57 0.56 0.55 0.1 Load Current (A) Figure 7. Frequency vs. Temperature IOUT=2A VIN 2V/div. VIN 2V/div. VLX 2V/div. VLX 2V/div. VOUT 500mV/div. VOUT 500mV/div. ILX 200mA/div. ILX 1A/div. 4ms/div. 4ms/div. Figure 8. Power On through VIN Waveform Figure 9. Power On through VIN Waveform FP6397-Preliminary 0.3-AUG-2019 6 FP6397 Typical Performance Curves (Continued) VIN=5V, VOUT=1.2V, C1=10μF, C2=10μF, L1=1.5μH, TA=+25°C, unless otherwise noted. IOUT=2A IOUT=0A VIN VLX 2V/div. VIN 2V/div. VLX 2V/div. 2V/div. VOUT 500mV/div. VOUT 500mV/div. ILX ILX 200mA/div. 20ms/div. 1A/div. 20ms/div. Figure 10. Power Off through VIN Waveform IOUT=0A Figure 11. Power Off through VIN Waveform IOUT=2A VEN 5V/div. VEN 5V/div. VLX 2V/div. VLX 2V/div. VOUT 500mV/div. VOUT 500mV/div. ILX 200mA/div. ILX 1A/div. 4ms/div. 4ms/div. Figure 12. Power On through EN Waveform Figure 13. Power On through EN Waveform IOUT=0A IOUT=2A VEN 5V/div. VEN 5V/div. VLX 2V/div. VLX 2V/div. VOUT 500mV/div. VOUT 500mV/div. ILX 200mA/div. ILX 1A/div. 4ms/div. 20μs/div. Figure 14. Power Off through EN Waveform Figure 15. Power Off through EN Waveform FP6397-Preliminary 0.3-AUG-2019 7 FP6397 Typical Performance Curves (Continued) VIN=5V, VOUT=1.2V, C1=10μF, C2=10μF, L1=1.5μH, TA=+25°C, unless otherwise noted. IOUT=2A IOUT=0A VLX VLX 2V/div. VOUT 50mV/div. VOUT 50mV/div. ILX ILX 2V/div. 1A/div. 200mA/div. 20ms/div 1μs/div Figure 16. Steady State Waveform Figure 17. Steady State Waveform IOUT=0.2A to 2A VOUT 100mV/div. ILX 1A/div. 80μs/div. Figure 18. Load Transient Waveform FP6397-Preliminary 0.3-AUG-2019 8 FP6397 Function Description The FP6397 is a high efficiency, internal compensation and constant frequency current mode step-down synchronous DC/DC regulator. It has integrated high-side (140mΩ, typ) and low-side (90mΩ, typ) power switches, and provides 2A continuous load current. It regulates input voltage from 2.5V to 6V, and down to an output voltage as low as 0.6V. Control Loop Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for superior load, line response, protection of the internal main switch and synchronous rectifier. The FP6397 switches at a constant frequency (1MHz) and regulates 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 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 peak inductor current is above the error voltage. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until next cycle starts. Enable The FP6397 EN pin provides digital control to turn on/off the regulator. When the voltage of EN exceeds the threshold voltage, the regulator will start the soft start function. If the EN 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 EN to VIN. Soft Start The FP6397 employs internal soft start function to reduce input inrush current during start up. The internal soft start time will be 1ms. Short Circuit Protection The FP6397 provides short circuit protection function to prevent the device damaged from short condition. When the short condition occurs and the feedback voltage drops lower than 40% of the regulation level, the oscillator frequency will be reduced and hiccup mode will be triggered to prevent the FP6397 from overheating during the extended short condition. Once the short condition is removed, the frequency and current limit will return to normal. Over Current Protection The FP6397 over current protection function is implemented by 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 FP6397 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 30°C (typ). PG Signal Output PG pin is an open-drain output and requires a pull up resistor. PG is actively held low in soft-start, standby and shutdown. It is released when the output voltage rises above 90% of nominal regulation point. Under Voltage Lockout When the FP6397 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 200mV (typ). FP6397-Preliminary 0.3-AUG-2019 9 FP6397 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 0.6V. Thus the output voltage is: V T =0. V 1+ Output Capacitor Selection R1 R2 Table 2 lists recommended values of R1 and R2 for most used output voltage. Table 2 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. Recommended Resistance Values VOUT R1 R2 3.3V 453kΩ 100kΩ 2.5V 316kΩ 100kΩ 1.8V 200kΩ 100kΩ 1.5V 150kΩ 100kΩ 1.2V 100kΩ 100kΩ 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: VR PPL t =VR PPL C +VR PPL t +VR PPL ( L) t +V R t t The following figures show the form of the ripple contributions. VRIPPLE(ESR)(t) Place resistors R1 and R2 close to FB pin to prevent stray pickup. 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: C (RM ) = = V V T 1 T + VRIPPLE(ESL) (t) (t) + VRIPPLE(C) (t) (t) + VNOISE (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. = VRIPPLE(t) (t) FP6397-Preliminary 0.3-AUG-2019 10 FP6397 Application Information (Continued) VR PPL ( R) = VR PPL ( L) = VR PPL (C) = V F T C L V V T R That will lower ripple current and result in lower output ripple voltage. The Δ L is inductor peak-to-peak ripple current: V L V F 1 L C 2 L= T L C 1 T V V V F T C 1 L V V 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. 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. 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 VOUT=1.2V, FOSC=1MHz 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. L= VOUT GND FP6397-Preliminary 0.3-AUG-2019 P A Load Current 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. V V V F V T C T L To guarantee sufficient output current, peak inductor current must be lower than the FP6397 high-side MOSFET current limit. The peak inductor current is shown as below: Ceramic Capacitor Inductor Selection T(MA ) = T(MA ) + L 2 IPEAK IOUT(MAX) ∆IL Time 11 FP6397 Application Information (Continued) Feed forward 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 feed forward capacitor C3 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: 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 (LX). 4. Multi-layer PCB design is recommended. C = 2 1 FCR 1 R1 1 1 + R1 R2 GND C1 VOUT L1 C3 VIN 4 3 LX PG 5 2 GND FB 6 1 EN R1 VIN R3 For optimizing the feed forward 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 feed forward capacitor identified, the value of feed forward capacitor C3 can be calculated with the following equation: C2 GND R2 Figure 19. Recommended Layout Diagram Where FCROSS is the cross frequency. To reduce transient ripple, the feed forward 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 feed forward capacitor value can be decreased to push the cross frequency to lower region. In general, the feed forward capacitor range is between 10pF to 330pF. FP6397-Preliminary 0.3-AUG-2019 12 FP6397 Outline Information SOT-23-5 Package (Unit: mm) SYMBOLS UNIT A A1 A2 B D E E1 e e1 L DIMENSION IN MILLIMETER MIN MAX 0.90 0.00 0.90 0.30 2.80 2.60 1.50 0.90 1.80 0.30 1.45 0.15 1.30 0.50 3.00 3.00 1.70 1.00 2.00 0.60 Note: Followed From JEDEC MO-178-C. Carrier Dimensions FP6397-Preliminary 0.3-AUG-2019 13 FP6397 Outline Information (Continued) SOT-23-6 Package (Unit: mm) SYMBOLS UNIT A A1 A2 B D E E1 e e1 L DIMENSION IN MILLIMETER MIN MAX 0.90 0.00 0.90 0.30 2.80 2.60 1.50 0.90 1.80 0.30 1.45 0.15 1.30 0.50 3.00 3.00 1.70 1.00 2.00 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. FP6397-Preliminary 0.3-AUG-2019 14