RC5037 FAIRCHILD | Alldatasheet

Document overview

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Technical content

Features

  • High power switch-mode DC-DC controller can provide in excess of 13A
  • Output voltage adjustable from 1.5V to 3.6V
  • 85% efficiency
  • Cumulative accuracy < 3% over line, load, and temperature variations
  • Overvoltage and short circuit protection
  • Built-in soft start

Applications

  • I/O and AGP power for desktop computers
  • High efficiency power for ASICs
  • High efficiency power for DSPs
  • Adjustable step-down power supplies

Description

The RC5037 is a high power, switch-mode DC-DC controller that provides efficient power for all low-voltage applications. This controller has a built-in Soft Start feature which offers system protection during power-up by reducing both inrush current and output overshoot. When combined with the appropriate external circuitry, the RC5037 can deliver load currents as high as 13A at efficiencies as high as 88%. The RC5037 can generate output voltages from 1.5V up to 3.6V using external resistors. The RC5037 is designed to operate in a constant on-time control mode under all load conditions. Its accurate low TC reference eliminates the need for precision external compo- nents in order to achieve the tight tolerance voltage regula- tion required by many applications. Short circuit current protection is provided through the use of a current sense resistor, while overvoltage protection is provided internally. Block Diagram Feedback Control Oscillator Digital Logic RC5037 1.5V Reference Vout +12V5V +5V RC5037 Adjustable Switching Regulator Controller

RC5037 PRODUCT SPECIFICATION Pin Assignments Absolute Maximum Ratings Note: 1. Functional operation under any of these conditions is not implied. Performance is guaranteed only if Operating Conditions are not exceeded. Operating Conditions Pin Descriptions Pin Name Pin Number Pin Function Description CEXT 1 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 Information for details. VCCA 2 Analog V cc Power supply for regulator control circuitry and voltage reference. Connect to system 5V supply and decouple to ground with 0.1µF ceramic capacitor. IFBH 3 High side current feedback. 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 Information for details. IFBL 4 Low side current feedback. See Applications Information for details. VFB 5 Voltage feedback. Using two external resistors, this pin sets the output voltage level for the switching regulator. GNDP 6 Power Ground. Connect to a low impedance ground. See Application Information for details. DRV 7 MOSFET driver output. Connect this pin to the gate of the N-channel MOSFET Q1 as shown in Figure 12. The trace from this pin to the MOSFET gate should be kept as short as possible (less than 0.5"). See Applications Information for details. VCCP 8 Power V cc Power supply for DRV output driver. Connect to system 12V supply with R-C filter shown in Figure 12. See Applications Information for details. Supply Voltages, VCCA 7V Supply Voltages, VCCP 13V Junction Temperature, T J +150°C Storage Temperature, T S -65 to +150°C Lead Soldering Temperature, 10 seconds 300°C Thermal Resistance Junction-to-Ambient, Q JA 163°C/W Parameter Conditions Min. Typ. Max. Units Switching Regulator Supply, VCCA 4.75 5 5.25 V Ambient Operating Temperature, T A 07 0 ° C Gate Drive Supply, VCCP 9.5 12 12.6 V CEXT VCCA IFBH VCCP DRV GNDP IFBL VFB RC5037

PRODUCT SPECIFICATION RC5037

Electrical Characteristics

(VCCA = 5V, VCCP = 12V, T A = 25 C using circuit of Figure 1, unless otherwise noted) The denotes specifications which apply over the full ambient operating temperature range. Notes: 1. Total DC accuracy includes setpoint accuracy, temperature drift, line and load regulation. 2. The on-time pulse width of the oscillator is set via external capacitor C EXT Parameter Conditions Min. Typ. Max. Units Output Voltage 1.5 3.6 V Output Temperature Drift T A = 0˚C–70˚C 40 ppm/˚C Line Regulation VCCA = 4.75 to 5.25V, I LOAD = 13A 3 5 mV Load Regulation I LOAD = 0 to 5A or 5A to 13A 30 43 mV V OUT PSRR VCCA = 4.75 to 5.25V 60 dB Output Ripple, peak-peak 20MHz BW, I LOAD = 13A 15 mV Total DC Accuracy ±55 ±100 mV Efficiency I LOAD = 5A 80 85 % Output Driver Current Open Loop 0.5 A Short Circuit Threshold Voltage 70 90 100 mV On Time Pulse Width C EXT = 180pF 3.5 µs VCCA Supply Current Independent of load 51 5 m A VCCP Supply Current I LOAD = 13A 20 25 mA

RC5037 PRODUCT SPECIFICATION Typical Operating Characteristics (VCCA = 5V, and T A = +25 C using circuit in Figure 1, unless otherwise noted) Output Current (A) Output Voltage vs. Load VOUT (%) 02 4 6 8 Output Voltage vs. Temperature, IOUT = 10A Nom. +0.25 +0.50 -0.25 -0.50 02 5 5 0 7 5 Output Voltage (%) +1.0 +0.5 Nom -0.5 -1.0 -1.5 +1.5 100 125 Transient Response, 0.5 to 5.5A ISW (2A/div) VOUT (50mV/div) Time (100µs/division) Output Ripple, IOUT = 10A) VOUT (10mV/division) Time (2µs/division) Efficiency vs. Output Current Efficiency (%) 12 3 4 5 Output Current 67 89 1 0

Figure 1. 13A at 3.3V Application Schematic

RC5037 PRODUCT SPECIFICATION Table1. Bill of Materials for a RC5037 3.3V, 13A Application Qty. Reference Manufacturer Part Order # Description Requirements and Comments

3 C1, C7-8 Any 100nF, 25V Capacitor

3 C2-4 Sanyo

1200µF, 10V Aluminum Capacitor I RMS = 2A , See Equation (2) in Applications Any 1µF, 25V Capacitor Any 180pF, 50V Capacitor C0G

6 C9-14 Sanyo

1500µF, 6.3V Aluminum Capacitor ESR = 44m W 1 R1 Any 47.5 W 1 R2 Any 4.75 W 1 R3 N/A 5.2m W , 1W Resistor PCB Trace Resistor, see Eauation (3) Applications 1 R4 Any 2.43K W

1 R5 Any 2K

W

1 D1 Motorola

15A, 45V Schottky

1 D2 Fairchild

1 D3 Motorola

6.2V Zener

1 Q1 Fairchild

30V, 14m W Logic Level MOSFET Optional L1 Any 2.5µH Inductor I SAT > 8A 1 L2 Any 4.7µH Inductor I SAT > 13A

1 U1 Fairchild

Application Information

The RC5037 contains a precision trimmed zero TC voltage reference, a constant-on-time architecture controller, a high current output driver, and a low offset error amp. The detailed block diagram in Figure 1 shows how the RC5037 works together with external components to achieve a high- performance switching power supply. Switch-Mode Control Loop The main control loop for the switch-mode converter consists of a current conditioning amplifier and a voltage conditioning amplifier. The voltage amplifier compares the voltage from the internal reference with the converter’s output voltage divided by an external resistor divider. The current amplifier senses the current by comparing the voltages at the IFBH and IFBL pins, which are attached to either side of the current sense resistor. The signals from the voltage and current amplifiers are summed together, the result being used to control the off-time of the oscillator. The current feedback signal is also used as part of the RC5037 short-circuit protection. High Current Output Drivers The RC5037 high current output driver (DRV) 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 RC5037 is a precision band-gap type reference. Its temperature coefficient is trimmed to provide a near zero TC. Constant-On-Time Oscillator The RC5037 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

capacitor voltage down to the lower comparator threshold. Figure 2. RC5037 Detailed Block Diagram so that we need 3 input capacitors. current flowing through the inductor in Figure 1 is 0.6A. Refer to Application Note AM-53 for detailed discussions.

accounts for the inductor ripple current. ommended that this node be converted to a plane if possible. of the regulator design. Since it is more common to use 1 oz. those layers to route the high current paths in the design. Figure 3. Examples of good and poor layouts trace length is kept under 0.5in.

PRODUCT SPECIFICATION RC5037 Mechanical Dimensions

8 Lead SOIC Package

D A – C – ccc C LEAD COPLANARITY SEATING PLANEe B L h x 45° C α EH A .053 .069 1.35 1.75 Symbol Inches Min. Max. Min. Max. Millimeters Notes A1 .004 .010 0.10 0.25 .020 0.51B .013 0.33 C .008 .010 0.20 0.25 E .150 .158 3.81 4.01 e .228 .244 5.79 6.20 .010 .020 0.25 0.50 H .050 BSC 1.27 BSC h L .016 .050 0.40 1.27 0° 8° 0° 8° N8 8 α ccc .004 0.10—— D .189 .197 4.80 5.00 Notes: Dimensioning and tolerancing per ANSI Y14.5M-1982. "D" and "E" do not include mold flash. Mold flash or protrusions shall not exceed .010 inch (0.25mm). "L" is the length of terminal for soldering to a substrate. Terminal numbers are shown for reference only. "C" dimension does not include solder finish thickness. Symbol "N" is the maximum number of terminals.

RC5037 PRODUCT SPECIFICATION 1/26/00 0.0m 001 Stock#DS30005037 Ó 1998 Fairchild Semiconductor Corporation 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

Ordering Information

ACEx™ CoolFET™ CROSSVOLT™ E 2CMOS TM FACT™ FACT Quiet Series™ FAST FASTr™ GTO™ HiSeC™ 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. 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 systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, or (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 significant injury to the user. 2. A critical component is 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. PRODUCT STATUS DEFINITIONS Definition of Terms Datasheet Identification Product Status Definition Advance Information Preliminary No Identification Needed Obsolete This datasheet contains the design specifications for product development. Specifications may change in any manner without notice. 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. This datasheet contains final specifications. Fairchild Semiconductor reserves the right to make changes at any time without notice in order to improve design. This datasheet contains specifications on a product that has been discontinued by Fairchild semiconductor. The datasheet is printed for reference information only. Formative or In Design First Production Full Production Not In Production 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. SyncFET™ TinyLogic™ UHC™ VCX™ ISOPLANAR™ MICROWIRE™ POP™ PowerTrench QFET™ QS™ Quiet Series™ SuperSOT™-3 SuperSOT™-6 SuperSOT™-8 Rev. D