FR9833SPCTR

FR9833 fitipower integrated technology lnc. 32V, 3A, 340KHz Synchronous Step-Down 85T DC/DC Converter Description Features The FR9833 is a synchronous step-down DC/DC converter that provides wide 6V to 32V input voltage range and 3A continuous load current capability.  The FR9833 fault protection includes cycle-by-cycle current limit, input UVLO, output over voltage protection and thermal shutdown. Besides, adjustable 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 compensation components and simplifies the design process. In shutdown mode, the supply current is less than 1μA. The FR9833 is available in an SOP-8 (exposed pad) packages, provides a very compact system solution and good thermal conductance. It is RoHS compliant and 100% lead (Pb) free.             Low RDS(ON) Integrated Power MOSFET (120mΩ/90mΩ) Wide Input Voltage Range: 6V to 32V Adjustable Output Voltage from 0.925V to 16V 3A Output Current Fixed 340kHz Switching Frequency Current Mode Operation Internal Compensation Function Adjustable Soft-Start Cycle-by-Cycle Current Limit Input Under Voltage Lockout Over Voltage Protection Over Temperature Protection with Auto Recovery SOP-8 Exposed Pad Package Applications     Car Charger LCD Display, TV Distributed Power System Networking, XDSL Modem Pin Assignments Ordering Information SP Package (SOP-8 Exposed Pad) FR9833□□□ TR: Tape/Reel BST 1 VIN LX 2 GND 3 4 9 GND 8 SS 7 SHDN NC 6 5 FB C: Green Package Type SP: SOP-8 (Exposed Pad) Figure 1. Pin Assignments of FR9833 FR9833-Preliminary 0.1-MAR-2014 1 FR9833 fitipower integrated technology lnc. 85T Typical Application Circuit C4 0.1μF R3 100kΩ 7 SHDN 2 VIN 12V to 32V C1 10μF MLCC C5 10μF MLCC 1 LX VIN 3 FR9833 6 NC VOUT 5V R1 30.9kΩ 1% FB GND 4,9 L1 10μH BST C6 (optional) 5 SS C2 47μF MLCC R2 6.98kΩ 1% 8 C3 0.1μF Figure 2. CIN /COUT use Ceramic Capacitors Application Circuit C4 0.1μF R3 100kΩ 7 SHDN 2 VIN 12V to 32V C1 100μF EC C5 0.1μF CERAMIC 1 BST LX VIN 3 FR9833 6 L1 10μH VOUT 5V R1 30.9kΩ 1% NC FB GND 4,9 SS 8 C6 (optional) 5 C2 100μF EC R2 6.98kΩ 1% C3 0.1μF Figure 3. CIN /COUT use Electrolytic Capacitors Application Circuit VIN VOUT C1 R1 R2 C5 C6 L1 C2 12V 3.3V 10μF MLCC 30.9kΩ 12kΩ 10μF MLCC 10pF~1nF 10μH 47μF MLCC 12V 5V 10μF MLCC 30.9kΩ 6.98kΩ 10μF MLCC 10pF~1nF 10μH 47μF MLCC 24V 5V 10μF MLCC 30.9kΩ 6.98kΩ 10μF MLCC 10pF~1nF 15μH 47μF MLCC 12V 3.3V 100μF EC 30.9kΩ 12kΩ 0.1μF -- 10μH 100μF EC 12V 5V 100μF EC 30.9kΩ 6.98kΩ 0.1μF -- 10μH 100μF EC 24V 5V 100μF EC 30.9kΩ 6.98kΩ 0.1μF -- 15μH 100μF EC Table 1. Recommended Component Values FR9833-Preliminary 0.1-MAR-2014 2 FR9833 fitipower integrated technology lnc. 85T Functional Pin Description Pin Name Pin No. SOP-8 (EP) Pin Function BST 1 High side gate drive boost pin. A capacitance 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. VIN 2 Power supply input pin. Placed input capacitors as close as possible from VIN to GND to avoid noise influence. LX 3 Power switching node. GND 4 Ground pin. FB 5 Feedback input pin. Connect FB and VOUT with a resistive voltage divider. This IC senses feedback voltage via FB and regulates it at 0.925V. NC 6 No connection. 7 Enable input pin. Pull high to turn on IC, and pull low to turn off IC. resistor for self-startup. SS 8 Soft-start pin. This pin controls the soft-start period. Connect a capacitor from SS to GND to set the soft-start period. Exposed Pad 9 Ground pin. The exposed pad must be soldered to a large PCB area and connected to GND for maximum power dissipation. Connect an external inductor to this switching node. Connect this pin to exposed pad. Connect VIN with a 100kΩ Block Diagram VIN UVLO & POR SHDN ISEN Internal Regulator OTP VCC VCC 1M OVP Oscillator BST High-Side MOSFET S 6µA FB Current Comp SS R OTP OVP UVLO PWM Control Driver Logic LX Low-Side MOSFET 0.925V Current Limit GND Figure 4. Block Diagram of FR9833 FR9833-Preliminary 0.1-MAR-2014 3 fitipower integrated technology lnc. FR9833 Absolute Maximum Ratings (Note 1) 85T ● Supply Voltage VIN ---------------------------------------------------------------------------------------- -0.3V to +34V ● Enable Voltage H ----------------------------------------------------------------------------------- -0.3V to +34V ● LX Voltage VLX ---------------------------------------------------------------------------------------------- -0.3V to VIN+0.3V ● BST Voltage VBST ------------------------------------------------------------------------------------------ -0.3V to VLX+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) (Note 2) SOP-8 (Exposed Pad) ------------------------------------------------------------------------ 60°C/W ● Package Thermal Resistance, (θJC) SOP-8 (Exposed Pad) ------------------------------------------------------------------------ 15°C/W Note 1：Stresses beyond this listed under “Absolute Maximum Ratings" may cause permanent damage to the device. Note 2：PCB heat sink copper area=10mm2. Recommended Operating Conditions ● Supply Voltage VIN ------------------------------------------------------------------------------------------- +6V to +32V ● Operation Temperature Range --------------------------------------------------------------------------- -40°C to +85°C FR9833-Preliminary 0.1-MAR-2014 4 FR9833 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 VIN Shutdown Supply Current ISD H =0V Feedback Voltage VFB Feedback OVP Threshold Voltage VOVP 1.5 V High-Side MOSFET RDS(ON) (Note3) RDS(ON) 120 mΩ Low-Side MOSFET RDS(ON) (Note3) RDS(ON) 90 mΩ High-Side MOSFET Leakage Current ILX(leak) High-Side MOSFET Current Limit (Note3) Low-Side MOSFET Current Limit (Note3) Oscillation Frequency Short Circuit Oscillation Frequency 6V≦VIN≦32V H 2 0.9 =0V, VLX=0V ILIMIT(HS) Minimum Duty ILIMIT(LS) From Drain to Source FOSC Maximum Duty Cycle DMAX Minimum On Time (Note3) TMIN Input UVLO Threshold VUVLO(Vth) Under Voltage Lockout Threshold Hysteresis VUVLO(HYS) 1 μA 0.95 V 10 4 290 FOSC(short) 0.925 mA μA 5 A 1.5 A 340 420 kHz VFB=0V 110 kHz VFB=0.8V 90 % 110 ns 5.5 V 250 mV VIN Rising Soft-Start Current ISS VSS=0V 6 μA External Soft-Start Period TSS CSS=0.1μF 15 ms H Input Low Voltage H (L) H Input High Voltage H (H) H Input Current Thermal Shutdown Threshold (Note3) H TSD 0.4 2 H =2V V V 2 μA 170 °C Note 3：Not production tested FR9833-Preliminary 0.1-MAR-2014 5 fitipower integrated technology lnc. FR9833 85T Function Description The FR9833 is a high efficiency, internal compensation and constant frequency current mode step-down synchronous DC/DC converter. It has integrated high-side (120mΩ, typ) and low-side (90mΩ, typ) power switches, and provides 3A continuous load current. It regulates input voltage from 6V to 32V, and down to an output voltage as low as 0.925V. Under Voltage Lockout When the FR9833 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 250mV (typ). Short Circuit Protection 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. The FR9833 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 0.4V, the oscillator frequency will be reduced to 110kHz to prevent the inductor current increasing beyond the current limit. In the meantime, the current limit will also be reduced to lower the short current. Once the short condition is removed, the frequency and current limit will return to normal. Over Current Protection Enable The FR9833 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. The FR9833 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 Soft-Start The FR9833 employs adjustable soft start function to reduce input inrush current during start up. When the device turns on, a 6μA current begins charging the capacitor which is connected from SS pin to GND. The equation for the soft start time is shown as below: T ms = C nF μA F The VFB voltage is 0.925V and the ISS current is 6μA. f a 0.1μF capacitor is connected from SS pin to GND, the soft-start time will be 15ms. The FR9833 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 60°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. Output Overvoltage Protection When the FB pin voltage exceeds 1.5V, the output overvoltage protection function will be triggered and turn off the high-side/low-side MOSFET. FR9833-Preliminary 0.1-MAR-2014 6 FR9833 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 0.925V. 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 =0.92 1 VOUT R1 R2 5V 30.9kΩ 6.98kΩ 3.3V 30.9kΩ 12kΩ 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: (RM ) = = 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 R R PPLE(E L) t E t t The following figures show the form of the ripple contributions. VRIPPLE(ESR)(t) + VRIPPLE(ESL) (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. + VRIPPLE(C) (t) (t) + VNOISE (t) (t) 1.75 1.5 3A IIN(RMS) (A) 1.25 1 2A 0.75 0.5 = VRIPPLE(t) 1A 0.25 0 10 20 30 40 50 60 70 80 90 D (%) FR9833-Preliminary 0.1-MAR-2014 (t) 7 FR9833 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 8 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 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=10μ 1.2 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. L=15μ 0.8 L=22μ 0.6 0.4 0.2 0 6 8 10 12 14 16 18 20 22 24 26 28 30 32 VIN (V) V OUT=5V, FOSC=340kHz 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 F PEA = Load Current Inductor Selection FR9833-Preliminary 0.1-MAR-2014 T C L To guarantee sufficient output current, peak inductor current must be lower than the FR9833 high-side MOSFET current limit. The peak inductor current is shown as below: Ceramic Capacitor 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 L= VOUT T 1 L T(MA ) L 2 IPEAK IOUT(MAX) ∆IL Time 8 FR9833 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 R1 FR9833 C6 2. Place feedback resistors close to the FB pin. 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 C6 can be calculated with the following equation: C6= 2 1 FCR 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. 1 R1 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. C6 1 1 R1 R2 C3 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. FR9833-Preliminary 0.1-MAR-2014 R1 R3 8 7 R2 6 5 Exposed GND Pad GND – C1 + – C5 1 2 3 VIN C2 + 4 LX L1 VOUT C4 Figure 5. Recommended PCB Layout Diagram 9 FR9833 fitipower integrated technology lnc. 85T Outline Information SOP-8 (Exposed Pad) Package (Unit: mm) SYMBOLS UNIT DIMENSION IN MILLIMETER MIN MAX A 1.25 1.70 A1 0.00 0.15 A2 1.25 1.55 B 0.31 0.51 D 4.80 5.00 D1 3.04 3.50 E 3.80 4.00 E1 2.15 2.41 e 1.20 1.34 H 5.80 6.20 L 0.40 1.27 Note：Followed From JEDEC MO-012-E. Carrier Dimensions Life Support Policy Fitipower’s products are not authorized for use as critical components in life support devices or other medical systems. FR9833-Preliminary 0.1-MAR-2014 10