www.fairchildsemi.com RC5036 Dual Adjustable Voltage Regulator Controller Features Description • Combines switching regulator and low dropout linear regulator in single chip • Linear regulator on/off control • Each output voltage adjustable from 1.5V to 3.6V • Built-in soft start • Switcher can be configured for 13A loads, linear for 5A • Precision trimmed low TC voltage reference • Constant On-Time oscillator • Small footprint 16 lead SOIC package The RC5036 combines a switch-mode DC-DC converter with a low-dropout linear regulator. In addition, it integrates the circuitry required to switch the DC-DC converter output between 3.5V and a user-selectable voltage from 1.5V to 3.6V as well as an enable function to allow the linear regulator to be turned off when not required. RC5036 has built-in soft start feature which offers system protection during power-up by reducing both inrush current and output overshoot. Applications • • • • RAMBUS or SDRAM power with ACPI support I/O and AGP power High efficiency power for DSPs Programmable dual power supply for high current loads With the appropriate external components, the DC-DC converter can deliver load current as high as 13A and the linear regulator can provide 5A. The DC-DC converter and the linear regulator can be set independently using two external resistors each to any value between 1.5V and 3.6V. The factory trimmed internal reference achieves tight tolerance voltage regulation on both outputs. Independent short circuit protection is also provided. Block Diagram +12V SWITCHING REGULATOR +5V FEEDBACK CONTROL SWITCHER SELECT OSCILLATOR DIGITAL LOGIC LINEAR REGULATOR LINEAR ENABLE 1.5V REFERENCE + – RC5036 REV. 2.0.0 RC5036 PRODUCT SPECIFICATION Pin Assignments LIN_EN 1 16 SWCTRL VREF 2 15 CEXT IFBH 3 14 GNDA IFBL 4 13 VSCL FBSW 5 12 LDRV VCCA 6 11 VCCL VFBL 7 10 VCCP GNDP 8 9 SDRV Pin Descriptions 2 Pin Name Pin Number LIN_EN 1 Linear regulator enable input. Accepts TTL/open collector input levels. A logic level HIGH on this pin disables the output of the linear regulator. VREF 2 Voltage reference test point. This pin provides access to the internal precision 1.5V bandgap reference and should be decoupled to ground using a 0.1µF ceramic capacitor. No load should be connected to this pin. IFBH 3 High side current feedback for switching regulator. Pins 3 and 4 are used as the inputs for the current feedback control loop and as the short circuit current sense points. Careful layout of the traces from these pins to the current sense resistor is critical for optimal performance of the short circuit protection scheme. See Applications Discussion for details. IFBL 4 Low side current feedback for switching regulator. See Applications Discussion for details. FBSW 5 Voltage feedback for switching regulator. This input is active when a logic level LOW is input on pin 16 (SWCTRL). Using two external resistors, it sets the output voltage level for the switching regulator. See Applications Discussion for details. VCCA 6 Switching Regulator Vcc. Power supply for switching regulator control circuitry and voltage reference. Connect to system 5V supply and decouple to ground with 0.1µF ceramic capacitor. VFBL 7 Voltage feedback for linear regulator. Using two external resistors, this pin sets the output voltage level for the linear regulator. See Applications Discussion for details. GNDP 8 Power Ground. Return pin for high currents flowing in pins 9, 10 and 12 (SDRV, VCCP and LDRV). Connect to a low impedance ground. See Applications Discussion for details. SDRV 9 FET driver output for switching regulator. Connect this pin to the gate of the N-channel MOSFET Q1 as shown in Figure 1. The trace from this pin to the MOSFET gate should be kept as short as possible (less than 0.5"). See Applications Discussion for details. VCCP 10 Switching regulator gate drive Vcc. Power supply for SDRV output driver. Connect to system 12V supply with R-C filter shown in Figure 1. See Applications Discussion for details. VCCL 11 Linear Regulator Vcc. Power supply for LDRV output op-amp. Connect to system 12V supply and decouple to ground with 0.1µF ceramic capacitor. LDRV 12 Output driver for linear regulator. Connect this pin to the base of an NPN transistor. When pin 1 (LIN_EN) is pulled HIGH, the linear regulator is disabled and pin 12 will be pulled low internally. VSCL 13 Low side current sense for linear regulator. Connect this pin between the sense resistor and the collector of the power transistor. The high side current sense is internally connected to pin 6 (VCCA). Layout is critical to optimal performance of the linear regulator short circuit protection scheme. See Applications Discussion for details. Pin Function Description RC5036 PRODUCT SPECIFICATION Pin Descriptions (continued) Pin Name Pin Number GNDA 14 Analog ground. All low power internal circuitry returns to this pin. This pin should be connected to system ground so that ground loops are avoided. See Applications Discussion for details. CEXT 15 External capacitor. A 180pF capacitor is connected to this pin as part of the constant on-time pulse width circuit. Careful layout of this pin is critical to system performance. See Applications Discussion for details. SWCTRL 16 Switching regulator control input. Accepts TTL/open collector input levels. A logic level HIGH on this pin presets the switching regulator output voltage at 3.5V using internal resistors. A logic level LOW on this pin will select the output voltage set by two external resistors and the voltage feedback control pin 5 (VFBSW). See Applications Discussion for details. Pin Function Description Absolute Maximum Ratings Supply Voltages, VCCA, VCCL, VCCP 13V Junction Temperature, TJ +150°C Storage Temperature, TS -65 to +150°C Lead Soldering Temperature, 10 seconds 300°C Thermal Resistance Junction-to-Ambient, ΘJA 112°C/W Note: 1. Functional operation under any of these conditions is not implied. Performance is guaranteed only if Operating Conditions are not exceeded. Operating Conditions Parameter Min. Typ. Max. Units Switching Regulator VCC, VCCA 4.75 5 5.25 V Linear Regulator VCC, VCCL 11.4 12 12.6 V 0.8 V V 70 °C 12.6 V Logic Inputs, SWCTRL, LIN_EN Ambient Operating Temperature, TA Drive Gate Supply, VCCP 3 Conditions Logic HIGH Logic LOW 2.4 0 9.5 12 PRODUCT SPECIFICATION RC5036 Electrical Characteristics—Switch-Mode Regulator (VCCA = 5V, VCCL = 12V, TA = 25°C using circuit of Figure 1, unless otherwise noted) The • denotes specifications which apply over the full ambient operating temperature range. Parameter Conditions Min. Typ. Max. Units VOSW1 SWCTRL = HIGH Set by internal resistors • Output Voltage, VOSW1 SWCTRL = LOW Set by external resistors • Setpoint Accuracy2 ISW = 5A Output Temperature Drift TA = 0°C–70°C Line Regulation VCCA = 4.75 to 5.25V ISW = 5A 0.10 0.15 %Vo Load Regulation ISW = 0 to 5A or 5A to 10A ±0.9 ±1.3 %Vo Output Ripple, peak-peak 20MHz BW, ISW = 5A Output Voltage, Cumulative DC Efficiency ISW = 5A Output Driver Current Open Loop Short Circuit Threshold Voltage CEXT = 180pF V 1.5 3.6 V -1.2 +1.2 %Vo • 40 ppm 15 • Accuracy3 On Time Pulse Width4 3.5 ±55 80 • 0.5 • 70 mV ±100 87 mV % A 90 3.5 100 mV µs Notes: 1. When the SWCTRL pin is HIGH or left open, the switch-mode regulator output will be preset at 3.5V using internal precision resistors. When the SWCTRL pin is LOW, the output voltage may be programmed with external resistors. Please refer to the Applications Section for output voltage selection information. 2. Setpoint accuracy is the initial output voltage variability under the specified conditions. When SWCTRL is LOW, the matching of the external resistors will have a major influence on this parameter. 3. Cumulative DC accuracy includes setpoint accuracy, temperature drift, line and load regulation, and output ripple. 4. The on-time pulse width of the oscillator is preset using external capacitor CEXT. See Typical Operating Characteristics curves. 4 RC5036 PRODUCT SPECIFICATION Electrical Characteristics—Linear Regulator (VCCA = 5V, VCCL = 12V, TA = 25°C using circuit in Figure 1, unless otherwise noted) The • denotes specifications which apply over the full ambient operating temperature range. Parameter Output Voltage, Setpoint Conditions VOL1 Accuracy2 Set by external resistors Min • IL=0.5A, using 0.1% resistors 1.5 -1.5 • Output Temperature Drift Typ Max Units 3.6 V +1.5 40 % ppm Line Regulation VCCL = 11.4V to 12.6V, IL = 3A 0.1 0.15 %Vo Load Regulation IL = 0 to 5A ±0.7 ±1 %Vo Output Noise 0.1 to 20KHz Cumulative DC Crosstalk4 ±1.7 ISW = 5A mV ±3 35 • Short Circuit Comparator Threshold Op-amp Output Current 1 • Accuracy3 Open Loop 40 50 50 70 % mVpp 60 mV mA Notes: 1. When the LIN_EN pin is LOW, the linear regulator output is set with external resistors. When the LIN_EN pin is HIGH, the linear regulator is disabled and will exhibit no output voltage. Please refer to the Application Section for output voltage selection information. 2. Setpoint accuracy is the initial output voltage variability under the specified conditions. The matching of the external resistors will have a major influence on this parameter. 3. Cumulative DC accuracy includes setpoint accuracy, temperature drift, line and load regulation. 4. Crosstalk is defined as the amount of switching noise from the switch-mode regulator that appears on the output of the linear regulator when both outputs are in a static load condition. Electrical Characteristics—Common (VCCA = 5V, VCCL = 12V, TA = 25°C using circuit of Figure 1, unless otherwise noted) The • denotes specifications which apply over the full ambient operating temperature range. Parameter Conditions Reference Voltage, VREF VREF PSRR 5 Min Typ Max Units 1.485 1.5 1.515 V 60 dB VCCA Supply Current Independent of load • 5 15 VCCP Supply Current ISW = 5A • 20 25 VCCL Supply Current IL = 2A • 5 mA mA mA RC5036 PRODUCT SPECIFICATION Typical Operating Characteristics (VCCA = 5V, VCCL = 12V and TA = +25°C using circuit in Figure 1, unless otherwise noted) Switcher Output Voltage vs. Load +1.5 +1.0 VOSW (%) Efficiency (%) Switcher Efficiency vs. Output Current 95 94 93 92 91 90 89 88 87 86 85 +0.5 Nom -0.5 3.5V 2.8V -1.0 -1.5 1 2 3 4 5 6 7 8 9 0 10 2 Switcher Output vs. Output Current 10 4 Output Voltage (V) 3 VOSW (V) 8 Linear Regulator Output vs. Output Current, Rsense = 7mΩ 4 2 1 0 3 2 1 0 8 10 12 14 0 16 Output Voltage vs. Temperature, ISW = 5A or ILR = 5A Nom. -0.25 -0.50 50 75 Temperature (˚C) 100 3 4 125 ISW (2A/div) VOSW (50mV/div) +0.25 25 2 5 6 Switcher Transient Response, 0.5A to 5.5A +0.50 0 1 Output Current (A) Output Current, ISW (A) Output Voltage (%) 6 Output Current (A) Output Current 6 4 Time (100µs/division) PRODUCT SPECIFICATION RC5036 Typical Operating Characteristics (continued) Switcher Output Ripple, IOUT = 10A Linear Output Startup, System Power-Up Time (2µs/division) Time (5ms/division) Switcher Output Startup, System Power-Up Time (5ms/division) Pin 9 (SDRV), 10A Load Time (1µs/division) Linear Output Startup, Using LIM_EN Pin Time (5ms/division) Pin 9 (SDRV), 0.1A Load Time (1µs/division) 7 8 GND +5V +12V C2 L1 Q3 CIN Optional 0.1µF C4 180pF 7mΩ Standby R2 0.1µF C1 Q2 14 15 16 9 10 11 U1 12 13 RC5036 4.7Ω R3 R1 C5 8 7 6 5 4 3 2 1 47Ω 0.1µF C3 1µF Q4 R7 10KΩ R8 6.65KΩ R4 5mΩ 4.7µH 0.1µF L2 C7 10nF D1 Q1 C6 R5 10KΩ R6 6.65KΩ COUT VCORE RC5036 PRODUCT SPECIFICATION Application Circuit Figure 1. RAMBUS Power with ACPI support, 10A Main, 100mA Standby RC5036 PRODUCT SPECIFICATION Table1. Bill of Materials for a RC5036 RAMBUS Application Qty. Reference Manufacturer Part Order # 4 C1-2, C5-6 Any 100nF, 25V Capacitor 1 C3 Any 1µF, 25V Capacitor 1 C4 Any 180pF, 50V Capacitor 1 C7 Any 10nF, 25V Capacitor 3 CIN Sanyo 10MV1200GX 1200µF, 10V Aluminum Capacitor IRMS = 2A , See Equation (2) in Applications 1 COUT Rubycon 6.3ZL1500M 1500µF, 6.3V Aluminum Capacitor ESR = 23mΩ 1 R1 Any 47.5Ω 1 R2 N/A 300mΩ 1 R3 Any 4.75Ω 1 R4 N/A 5mΩ PCB Trace Resistor, 1W 2 R5, R7 Any 10KΩ 2 R6, R8 Any 6.65KΩ 1 D1 Motorola MBRB1545CT 15A, 45V Schottky 1 Q1 Fairchild FDB6030L 30V, 14mΩ Logic Level MOSFET 3 Q2-4 Fairchild MMBT2222A 40V, 1A NPN Any 2.5µH Inductor ISAT > 8A ISAT > 13A Optional L1 L2 Any 4.7µH Inductor 1 U1 Fairchild RC5036M PWM Controller The RC5036 contains a precision trimmed zero TC voltage reference, a constant-on-time architecture controller, a high current switcher output driver, a low offset op-amp, and switches for selecting various output modes. The block diagram in Figure 2 shows how the RC5036 in combination with the external components achieves a switchable dual power supply. Switch-Mode Control Loop The main control loop for the switch-mode converter consists of a current conditioning amplifier and one of the two voltage conditioning amplifiers that take the raw voltage and current information from the regulator output, compare them against the precision reference and present the error signal to the input of the constant-on-time oscillator. The two voltage conditioning amplifiers act as an analog switch to select C0G PCB Trace Resistor, see Applications 1 Application Information 9 Requirements and Comments Description PCB Trace Resistor, see Applications between the internal resistor divider network (set for 3.5V) or an external resistor divider network (adjustable for 1.5V to 3.6V.) The switch-mode select pin determines which of the two amplifiers is selected. The current feedback signals come across the Iout sense resistor to the IFBH and IFBL inputs of the RC5036. The error signals from both the current feedback loop and the voltage feedback loop are summed together and used to control the off-time duration of the oscillator. The current feedback error signal is also used as part of the RC5036 short-circuit protection. Linear Control Loop The low-offset op-amp is configured to be the controlling element in a precision low-drop-out linear regulator. As can be seen from Figure 2, the op-amp is used to compare the divided down output of the linear regulator to the precision reference. The error signal is used to control either an N-channel MOSFET or a power NPN transistor. RC5036 PRODUCT SPECIFICATION High Current Output Drivers charged and discharged through the enabling and disabling of the fixed current source. The variable current source is controlled from the error inputs that are received from the current and voltage feedback signals. The oscillator off-time is controlled by the amount of current that is available from the variable current source to charge the external capacitor up to the high threshold level of the comparator. The on-time is set be the constant current source that discharges the external capacitor voltage down to the lower comparator threshold. The RC5036 switching high current output driver (SDRV) contains high speed bipolar power transistors configured in a push-pull configuration. The output driver is capable of supplying 0.5A of current in less than 100ns. The driver’s power and ground are separated from the overall chip power and ground for added switching noise immunity. Internal Reference The reference in the RC5036 is a precision band-gap type reference. Its temperature coefficient is trimmed to provide a near zero TC. For guaranteed stable operation under all conditions, a 0.1µF capacitor is recommended on the VREF output pin. No load may be attached to this pin. Using SWCTRL and LIM_EN When the SWCTRL pin is HIGH, the switching regulator will set its output at 3.5V using two internal precision resistors. When this pin is LOW, the switching regulator output can be set to any voltage between 1.5V and 3.6V using external precision resistors. The LIN_EN pin is used to enable or disable the linear regulator. When the LIN_EN pin is HIGH, the linear regulator will be disabled. If this pin is LOW, the linear regulator output can be set from 1.5V to 3.5V using external precision resistors. The linear regulator output can be left on to provide power to other 3.3V components. Constant-On-Time Oscillator The RC5036 switch-mode oscillator is designed as a fixed on-time, variable off-time oscillator. The constant-on-time oscillator consists of a comparator, an external capacitor, a fixed current source, a variable current source, and an analog switch that selects between two threshold voltages for the comparator. The external timing capacitor is alternately +5V +12V gm gm CONSTANT ON-TIME OSCILLATOR gm IO ANALOG SWITCH VH VL VOSW ION +12V VREF REF + – VOL RC5036 SWCTRL SWITCHER SELECT LINEAR ENABLE LIN_EN Figure 2. RC5036 Block Diagram 10 PRODUCT SPECIFICATION RC5036 Output Voltage Selection Linear Regulator Design Considerations The RC5036 precision reference is trimmed to be 1.5V nominally. When using the RC5036, the system designer has complete flexibility in choosing the output voltage for each regulator from 1.5V to 3.6V. This is done by appropriately selecting the feedback resistors. These could be 0.1% resistors to realize optimum output accuracy. The following equations determine the output voltages of the two regulators: Figure 1 shows the application schematic for the RC5036 with an NPN used for the linear regulator. Careful consideration must be given to the base current of the power NPN device. The base current to the power NPN device is limited by: • The RC5036 op-amp output current (50mA) Switching Regulator: V OUT • The internal power dissipation of the RC5036 package R6 + R5 = 1.5 × --------------------- R5 • The β of the power NPN device. The internal RC5036 power dissipation is the most severe limitation for this application. For optimum reliability, we require that the junction temperature not exceed 130°C; thus we can calculate the maximum power dissipation allowable for this 16-lead SOIC package as follows: Linear Regulator: R8 + R7 V OUT = 1.5 × --------------------- R7 where R6 > 1.5kΩ and (R5 + R6) ≤ 25kΩ and R8 > 1.5kΩ and (R7 + R8) ≤ 25kΩ T J ( max ) – T A P D = ------------------------------R ΘJA Example: If we assume that the ambient temperature TA is 70°C and the thermal resistance of the 16-lead SOIC package is 112°C/W, then the maximum power dissipation for the IC is: For 3.3V, R6 + R5 6.65k + 10k V OUT = 1.5 × --------------------- = 1.5 × ----------------------------- = 3.3V R5 10k 130 – 70 P D = --------------------- ≤ 0.533W 112 P D = P SW + P LR = Input Capacitors The number of input capacitors required for the RC5036 is dependent on their ripple current rating, which assures their rated life. The number required may be determined by 2 I out * DC – DC No. Caps = --------------------------------------I rating (2) where the duty cycle DC = Vout/Vin. For example, with a 1.5V output at 10A, 5V input, and using the Sanyo capacitors specified in Table 1 which have a 2A ripple current rating, we have DC = 1.5/5 = 0.3, and ( 35mA × 5.25V ) + ( 12.6V – V OUT – V BE ) × I OL ≤ 0.533W where PSW is the internal power dissipation of the switching regulator and PLN is the internal power dissipation of the linear regulator. IOL is the linear regulator op-amp output current. For VOUT = 3.3V nominal, the worst case output will be determined by the current used. For example, for a worst case VOUT = 3.135V, the maximum op-amp output current is: 0.533W – ( 35mA × 5.25V ) I OL = ------------------------------------------------------------------- ≤ 40mV ( 12.6V – 3.135V – 0.8V ) 2 10* 0.03 – 0.3 No. Caps = ------------------------------------ = 2.29 2 so that we need 3 input capacitors. 3000mA β ≥ --------------------- = 75 40mA The power NPN transistor must have a minimum β of 75 at IL = 3A in order to meet the internal power dissipation limit of the 16-SOIC package. 11 RC5036 PRODUCT SPECIFICATION Short Circuit Considerations Schottky Diode For the Switch-Mode Regulator In Figure 1, MOSFET Q1 and flyback diode D1 are used as complementary switches in order to maintain a constant current through the output inductor L1. As a result, D1 will have to carry the full current of the output load when the power MOSFET is turned off. The power in the diode is a direct function of the forward voltage at the rated load current during the off time of the FET. The following equation can be used to estimate the diode power: The RC5036 uses a current sensing scheme to limit the load current if an output fault condition occurs. The current sense resistor carries the peak current of the inductor, which is greater than the maximum load current due to ripple currents flowing in the inductor. The RC5036 will begin to limit the output current to the load by turning off the top-side FET driver when the voltage across the current-sense resistor exceeds the short circuit comparator threshold voltage (Vth). When this happens the output voltage will temporarily go out of regulation. As the voltage across the sense resistor becomes larger, the top-side MOSFET will continue to turn off until the current limit value is reached. At this point, the RC5036 will continuously deliver the limit current at a reduced output voltage level. The short circuit comparator threshold voltage is typically 90mV, with a variability of ±10mV. The ripple current flowing through the inductor is typically 0.5A. Refer to Application Note AM-53 for detailed discussions. The sense resistor value can be approximated as follows: V th,min V th,min R SENSE = ---------------- × ( 1 – TF ) = --------------------------------------------- × ( 1 – TF ) I PK 0.5A + I LOAD,MAX where TF = Tolerance Factor for the sense resistor and 0.5A accounts for the inductor current ripple. P DIODE = I D × V D × ( 1 – DutyCycle ) where ID is the forward current of the diode, VD is the forward voltage of the diode, and DutyCycle is defined the same as Vout Duty Cycle = ------------Vin For the Motorola MBRB1545CT Power Rectifier used in Figure 1, P DIODE = 10A × 0.65 × ( 1 – 73.1% ) = 1.75W It is recommended that the diode T0-220 package be attached to a heatsink. Board Design Considerations Since the value of the sense resistor is often less than 10mΩ, care should be taken in the layout of the PCB. Trace resistance can contribute significant errors. The traces to the IFBH and IFBL pins of the RC5036 should be Kelvin connected to the pads of the current-sense resistor. To minimize the influence of noise, the two traces should be run next to each other. For the Linear Regulator The analysis for short circuit protection of the linear regulator is much simpler than that of the switching regulator. The formula for the inception point of short-circuit protection for the linear regulator is: V th,min R SENSE = --------------------------- × ( 1 – TF ) I LOAD,MAX Vth = 45mV ± 8mV and ILOAD,MAX = 5A, 37mV R SENSE = --------------- × ( 1 – 29% ) = 5.3mΩ for using an 5A embedded PC trace resistor 37mV R SENSE = --------------- × ( 1 – 5% ) = 7.0mΩ for using a 5A discrete resistor 12 RC5036 Placement Preferably the PC layer directly underneath the RC5036 should be the ground layer. This serves as extra isolation from noisy power planes. MOSFET Placement Placement of the power MOSFET is critical in the design of the switch-mode regulator. The FET should be placed in such a way as to minimize the length of the gate drive path from the RC5036 SDRV pin. This trace should be kept under 0.5" for optimal performance. Excessive lead length on this trace causes high frequency noise resulting from the parasitic inductance and capacitance of the trace. Since this voltage can transition nearly 12V in around 100nsec, the resultant ringing and noise will be very difficult to suppress. This trace should be routed on one layer only and kept well away from the “quiet” analog pins of the device: VREF, CEXT, FBSW, IFBH, IFBL, and VFBL. Refer to Figure 3. Inductor and Schottky Diode Placement The inductor and fly-back Schottky diode must be placed close to the source of the power MOSFET. The node connecting the inductor and the diode swing between the drain voltage of the FET and the forward voltage of the Schottky diode. It is recommended that this node be converted to a plane if possible. This node is part of the high current path in the design, and is best treated as a plane to minimize the parasitic resistance and inductance on that node. RC5036 PRODUCT SPECIFICATION Most PC board manufacturers utilize 1/2oz copper on the top and bottom signal layers of the PCB; thus, it is not recommended to use these layers to rout the high current portions of the regulator design. Since it is more common to use 1 oz. copper on the PCB inner layers, it is recommended to use those layers to route the high current paths in the design. range of frequencies. The low ESR capacitors on the input side (5V) of the FET must be located close to the drain of the power FET. Minimizing parasitic inductance and resistance is critical in supressing the ringing and noise spikes on the power supply. The output low ESR capacitors need to be placed close to the output sense resistor to provide good decoupling at the voltage sense point. One of the characteristics of good low ESR capacitors is that the impedance gradually increases as the frequency increases. Thus for high frequency noise supression, good quality low inductance ceramic capacitors need to be placed in parallel with the low ESR bulk capacitors. These can usually be 0.1µF 1206 surface mount capacitors. Capacitor Placement One of the keys to a successful switch-mode power supply design is correct placement of the low ESR capacitors. Decoupling capacitors serve two purposes; first there must be enough bulk capacitance to support the expected transient current, and second, there must be a variety of values and capacitor types to provide noise supression over a wide Example of a Problem layout Example of a Good layout SDRV Noisy Signal is routed away from quiet pins and trace length is kept under 0.5 in. CEXT SWDRV 9 8 9 8 10 7 10 7 11 6 11 6 12 5 12 5 13 4 IFBL 13 4 IFBL 14 3 IFBH 14 3 IFBH 15 2 VREF 15 2 VREF 16 1 16 1 = “Quiet” Pins CEXT Noisy Signal radiates onto quiet pins and trace is too long. Figure 3. Examples of good and poor layouts Power and Ground Connections The connection of VCCA to the 5V power supply plane should be short and bypassed with a 0.1µF directly at the VCCA pin of the RC5036. The ideal connection would be a via down to the 5V power plane. A similar arrangement should be made for the VCCL pin that connects to +12V, though this one is somewhat less critical since it powers only the linear op-amp. Each ground should have a separate via connection to the ground plane below. MOSFET Gate Bias +12V +5V 47 W VCCP Q1 SDRV VO L1 1uF RSENSE D1 CBULK GNDP Figure 4. 12V Gate Bias Configuration 13 RC5036 A 12V power supply is used to bias the VCCP. A 47Ω resistor is used to limit the transient current into VCCP. A 1uF capacitor filter is used to filter the VCCP supply and source the transient current required to charge the MOSFET gate capacitance. This method provides sufficiently high gate bias voltage to the MOSFET (VGS), and therefore reduces RDS(ON) of the MOSFET and its power loss. Figure 4 provides about 5V of gate bias which works well when using typical logic-level MOSFETs. Layout Gerber File and Silk Screen A reference design for motherboard implementation of the RC5036 along with the Layout Gerber File and the Silk Screen is available. Please call Fairchild Electronics Semiconductor Division’s Marketing Departmentat 408-822-2550 to obtain this information. 14 PRODUCT SPECIFICATION RC5036 Evaluation Board Fairchild Electronics Semiconductor Division provides an evaluation board for verifying the system level performance of the RC5036. The evaluation board provides a guide as to what can be expected in performance with the supplied external components and PCB layout. Please call your local Sales Office or Fairchild Electronics Semiconductor Division at 408-822-2550 for an evaluation board. PRODUCT SPECIFICATION RC5036 Mechanical Dimensions 16-Lead SOIC Package Inches Symbol Min. A A1 B C D E e H h L N α ccc Millimeters Max. Min. 1.35 1.75 0.10 0.25 0.33 0.51 0.19 0.25 9.80 10.00 3.81 4.00 1.27 BSC .228 .010 .016 5.80 0.25 0.40 16 6.20 0.50 1.27 16 0° 8° 0° 8° — .004 — 0.10 16 1. Dimensioning and tolerancing per ANSI Y14.5M-1982. Max. .053 .069 .004 .010 .013 .020 .008 .010 .386 .394 .150 .158 .050 BSC .244 .020 .050 Notes: Notes 2. "D" and "E" do not include mold flash. Mold flash or protrusions shall not exceed .010 inch (0.25mm). 3. "L" is the length of terminal for soldering to a substrate. 4. Terminal numbers are shown for reference only. 5 2 2 5. "C" dimension does not include solder finish thickness. 6. Symbol "N" is the maximum number of terminals. 3 6 9 E 1 H 8 h x 45° D C A1 A α e B SEATING PLANE –C– LEAD COPLANARITY L ccc C 15 RC5036 PRODUCT SPECIFICATION Ordering Information Product Number RC5036M Package 16 pin SOIC LIFE SUPPORT POLICY FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. 2. A critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com 1/26/00 0.0m 001 Stock#DS30005036 1998 Fairchild Semiconductor Corporation TRADEMARKS The following are registered and unregistered trademarks Fairchild Semiconductor owns or is authorized to use and is not intended to be an exhaustive list of all such trademarks. ISOPLANAR™ MICROWIRE™ POP™ PowerTrench QFET™ QS™ Quiet Series™ SuperSOT™-3 SuperSOT™-6 SuperSOT™-8 ACEx™ CoolFET™ CROSSVOLT™ E2CMOSTM FACT™ FACT Quiet Series™ FAST® FASTr™ GTO™ HiSeC™ SyncFET™ TinyLogic™ UHC™ VCX™ DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or 2. A critical component is any component of a life support device or system whose failure to perform can systems which, (a) are intended for surgical implant into be reasonably expected to cause the failure of the life the body, or (b) support or sustain life, or (c) whose support device or system, or to affect its safety or failure to perform when properly used in accordance with instructions for use provided in the labeling, can be effectiveness. reasonably expected to result in significant injury to the user. PRODUCT STATUS DEFINITIONS Definition of Terms Datasheet Identification Product Status Definition Advance Information Formative or In Design This datasheet contains the design specifications for product development. Specifications may change in any manner without notice. Preliminary First Production This datasheet contains preliminary data, and supplementary data will be published at a later date. Fairchild Semiconductor reserves the right to make changes at any time without notice in order to improve design. No Identification Needed Full Production This datasheet contains final specifications. Fairchild Semiconductor reserves the right to make changes at any time without notice in order to improve design. Obsolete Not In Production This datasheet contains specifications on a product that has been discontinued by Fairchild semiconductor. The datasheet is printed for reference information only. Rev. D