FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Features Description The FAN2106 TinyBuck™ is an easy-to-use, cost and space-efficient, 6A synchronous buck solution. It enables designers to solve high current requirements in a small area with minimal external components. 6A Output Current Over 95% Efficiency Fully Synchronous Operation with Integrated Schottky Diode on Low-side MOSFET Boosts Efficiency Programmable Frequency Operation: 200KHz to 600KHz Power-good Signal Accepts Ceramic Capacitors on Output External Compensation for Flexible Design Wide Input Range: 3V to 24V Output Voltage Range: 0.8V to 90% VIN External compensation, programmable switching frequency, and current limit features allow for design optimization and flexibility. The summing current mode modulator uses lossless current sensing for current feedback and over-current, and includes voltage feedforward. Fairchild’s advanced BiCMOS power process combined with low-RDS(ON) internal MOSFETs and a thermally efficient MLP package provide the ability to dissipate high power in a small package. Programmable Current Limit Output over voltage, under voltage, and thermal shutdown protections help protect the device from damage during fault conditions. Under-voltage, Over-voltage, and Thermal Protections Related Application Notes 5x6mm, 25-pin, 3-pad MLP Input Under-voltage Lockout AN-6033 — FAN2106 Design Guide Applications Graphics Cards Battery-powered Equipment Set-top Boxes Point-of-load Regulation Servers Ordering Information Part Number Operating Temperature Range Package FAN2106MPX -10°C to 85°C Molded Leadless Package (MLP) 5x6mm Green Tape and Reel FAN2106EMPX -40°C to 85°C Molded Leadless Package (MLP) 5x6mm Green Tape and Reel Eco Status Packing Method For Fairchild’s definition of “green” please visit: http://www.fairchildsemi.com/company/green/rohs_green.html. © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 www.fairchildsemi.com FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator May 2008 Figure 1. Typical Application Block Diagram FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Typical Application Diagram Figure 2. Block Diagram © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 www.fairchildsemi.com 2 Figure 3. MLP 5x6mm Pin Configuration (Bottom View) Pin Definitions Pin # Name Description P1, 6-12 SW Switching Node. P2, 2-5 VIN Power Input Voltage. Connect to the main input power source. P3, 21-23 PGND Power Ground. Power return and Q2 source. 1 BOOT High-Side Drive BOOT Voltage. Connect through capacitor (CBOOT) to SW. The IC includes an internal synchronous bootstrap diode to recharge the capacitor on this pin to VCC when SW is LOW. 13 PGOOD Power-Good Flag. An open-drain output that pulls LOW when FB is outside a ±10% range of the reference. PGOOD does not assert HIGH until the fault latch is enabled. 14 EN ENABLE. Enables operation when pulled to logic HIGH or left open. Toggling EN resets the regulator after a latched fault condition. This input has an internal pull-up when the IC is functioning normally. When a latched fault occurs, EN is discharged by a current sink. 15 VCC 16 AGND 17 ILIM Current Limit. A resistor (RILIM) from this pin to AGND can be used to program the currentlimit trip threshold lower than the default setting. 18 R(T) Oscillator Frequency. A resistor (RT) from this pin to AGND sets the PWM switching frequency. 19 FB Output Voltage Feedback. Connect through a resistor divider to the output voltage. 20 COMP Compensation. Error amplifier output. Connect the external compensation network between this pin and FB. 24 NC 25 RAMP FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Pin Configuration Input Bias Supply for IC. The IC’s logic and analog circuitry are powered from this pin. Analog Ground. The signal ground for the IC. All internal control voltages are referred to this pin. Tie this pin to the ground island/plane through the lowest impedance connection. No Connect. This pin is not used. Ramp Amplitude. A resistor (RRAMP) connected from this pin to VIN sets the ramp amplitude and provides voltage feedforward functionality. © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 www.fairchildsemi.com 3 Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. Parameter Conditions Min. VIN to PGND VCC to AGND AGND = PGND SW to PGND Continuous 28 V 6 V V -0.3 6.0 V -0.5 24.0 V -5 30 V -0.3 VCC+0.3 V Transient (t < 20ns, f < 600KHz) All other pins Unit 35 BOOT to PGND BOOT to SW Max. Recommended Operating Conditions The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend exceeding them or designing to absolute maximum ratings. Symbol Parameter Conditions VCC Bias Voltage VCC to AGND VIN Supply Voltage VIN to PGND TA Ambient Temperature TJ Junction Temperature Min. Typ. Max. Unit 4.5 5.0 5.5 V 3 24 V FAN2106M -10 +85 °C FAN2106EM -40 +85 °C +125 °C Max. Unit +150 °C Thermal Information Symbol TSTG Parameter Min. Storage Temperature Typ. -65 TL Lead Soldering Temperature, 10 Seconds +300 °C TVP Vapor Phase, 60 Seconds +215 °C TI Infrared, 15 Seconds +220 °C θJC Thermal Resistance: Junction-to-Case P1 (Q2) θJ-PCB PD °C/W P2 (Q1) 7 °C/W P3 4 °C/W Thermal Resistance: Junction-to-Mounting Surface Power Dissipation, TA = 25°C 4 35 FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Absolute Maximum Ratings (1) °C/W 2.8 (1) W Note: 1. Typical thermal resistance when mounted on a four-layer, two-ounce PCB, as shown in Figure 25. Actual results are dependent on mounting method and surface related to the design. © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 www.fairchildsemi.com 4 Recommended operating conditions are the result of using the circuit shown in Figure 1 unless otherwise noted. Parameter Conditions Min. Typ. Max. Unit SW = Open, FB = 0.7V, VCC = 5V, fSW = 600KHz 8 12 mA Shutdown: EN = 0, VCC = 5V 7 10 µA 4.3 4.5 V Power Supplies VCC Current Rising VCC VCC UVLO Threshold 4.1 Hysteresis 300 mV Oscillator Frequency Minimum On-Time 255 300 345 KHz RT = 24KΩ 540 600 660 KHz 50 65 ns (2) 16VIN, 1.8VOUT, RT = 30KΩ, RRAMP = 200KΩ Ramp Amplitude, pk–pk Minimum Off-Time RT = 50KΩ 0.53 (2) V 100 150 ns 794 800 806 mV 795 800 805 mV 80 85 dB 12 15 MHz Reference Reference Voltage (VFB) FAN2106M, 25°C (See Figure 4 for Temperature Coefficient) FAN2106EM, 25°C Error Amplifier DC Gain (2) Gain Bandwidth Product (2) VCC = 5V Output Voltage (VCOMP) 0.4 3.2 V Output Current, Sourcing VCC = 5V, VCOMP = 2.2V 1.5 2.2 mA Output Current, Sinking VCC = 5V, VCOMP = 1.2V 0.8 1.2 mA FB Bias Current VFB = 0.8V, 25°C -850 -650 -450 6 8 10 A -11 -10 -9 µA nA Protection and Shutdown Current Limit RILIM Open ILIM Current Over-Temperature Shutdown Over-Temperature Hysteresis +155 Internal IC Temperature FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Electrical Specifications °C +30 °C Over-Voltage Threshold 2 Consecutive Clock Cycles 110 115 120 %VOUT Under-Voltage Shutdown 16 Consecutive Clock Cycles 68 73 78 %VOUT Fault Discharge Threshold Measured at FB Pin 250 mV Fault Discharge Hysteresis Measured at FB Pin (VFB ~500mV) 250 mV 5.3 ms 6.7 ms Soft-Start VOUT to Regulation (T0.8) Fault Enable/SSOK (T1.0) Frequency = 600KHz Note: 2. Specifications guaranteed by design and characterization; not production tested. © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 www.fairchildsemi.com 5 Recommended operating conditions are the result of using the circuit shown in Figure 1 unless otherwise noted. Parameter Conditions Min. Typ. Max. Unit EN Threshold, Rising 1.35 2.00 V EN Hysteresis 250 mV 800 KΩ 1 µA Control Functions EN Pull-Up Resistance EN Discharge Current Auto-restart mode FB OK Drive Resistance 800 Ω PGOOD Threshold (Compared to VREF) FB < VREF -14 -11 -8 %VREF FB > VREF +7 +10 +13 %VREF PGOOD Output Low IOUT < 2mA 0.4 V © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Electrical Specifications (Continued) www.fairchildsemi.com 6 1.20 1.005 1.10 I FB V FB 1.010 1.000 0.995 1.00 0.90 0.990 0.80 -50 0 50 100 150 -50 0 Temperature (oC) Figure 4. Reference Voltage (VFB) vs. Temperature, Normalized 150 1.02 1200 1.01 Frequency Frequency (KHz) 100 Figure 5. Reference Bias Current (IFB) vs. Temperature, Normalized 1500 900 600 600KHz 1.00 300KHz 0.99 300 0.98 0 0 20 40 60 80 100 120 -50 140 0 RT (KΩ) 50 100 150 o Temperature ( C) Figure 6. Frequency vs. RT Figure 7. Frequency vs. Temperature, Normalized 1.04 1.60 1.40 1.02 1.20 I ILIM RDS 50 Temperature (oC) FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Typical Characteristics 1.00 1.00 o Q1 ~0.32 %/ C 0.80 0.98 o Q2 ~0.35 %/ C 0.96 0.60 -50 0 50 100 150 -50 50 100 150 Temperature ( C) Temperature ( C) Figure 9. Figure 8. RDS vs. Temperature, Normalized (VCC = VGS = 5V) © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 0 o o ILIM Current (IILIM) vs. Temperature, Normalized www.fairchildsemi.com 7 Figure 10. Application Circuit: 1.8VOUT, 500KHz Typical Performance Characteristics 100 1400 95 1200 Dissipation (mW) Efficiency (%) Typical operating characteristics using the circuit shown in Figure 10. VIN=16V, VCC=5V, unless otherwise specified. 90 85 8VIN 12VIN 18VIN 80 75 1000 8VIN 12VIN 18VIN 800 600 400 200 70 0 0 1 2 3 4 5 6 0 1 2 Load (A) 1.8VOUT Efficiency Over VIN vs. Load 100 95 95 90 85 VIN=12V 300KHz 500KHz 700KHz 75 5 6 Figure 12. 1.8VOUT Dissipation Over VIN vs. Load 100 80 4 Load (A) Efficiency (%) Efficiency (%) Figure 11. 3 FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Application Circuit 90 8VIN, 300KHz 85 12VIN, 500KHz 80 18VIN, 700KHz 75 70 70 0 1 2 3 4 5 0 6 2 3 4 5 6 Load (A) Load (A) Figure 13. 1.8VOUT Efficiency Over Frequency vs. Load (Circuit Value Changes) © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 1 Figure 14. 3.3VOUT Efficiency vs. Load (Circuit Value Changes) www.fairchildsemi.com 8 Typical operating characteristics using the circuit shown in Figure 10. VIN=16V, VCC=5V, unless otherwise specified. VOUT VOUT SW SW Figure 15. SW and VOUT Ripple, 6A Load Figure 16. Start up with 1V Pre-Bias on Vout VOUT EN IOUT SW Figure 17. Transient Response, 2-6A Load Figure 18. VOUT Re-start on Fault FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Typical Performance Characteristics (Continued) VOUT PGOOD PGOOD EN EN Figure 19. Start-Up, 3A Load © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 Figure 20. Shutdown, 3A Load www.fairchildsemi.com 9 The regulator does not allow the low-side MOSFET to operate in full synchronous rectification mode until internal SS ramp reaches 95% of VREF (~0.76V). This helps the regulator to start on a pre-biased output and ensures that inductor current does not "ratchet" up during the soft-start cycle. Application Note AN-6033 — FAN2106 Design Guide includes a spreadsheet design aid to calculate external component values and verify loop stability given the following inputs: Output voltage Input voltage range Maximum output load current Maximum load transient current and maximum allowable output drop during load transient Maximum allowable output ripple Desired switching frequency VCC UVLO or toggling the EN pin discharges the SS and resets the IC. Bias Supply The FAN2106 requires a 5V supply rail to bias the IC and provide gate-drive energy. Connect a ≥ 1.0µf X5R or X7R decoupling capacitor between VCC and PGND. Download AN-6033 — FAN2106 Design Guide at: http://www.fairchildsemi.com/an/AN/AN-6033.pdf Since VCC is used to drive the internal MOSFET gates, supply current is frequency and voltage dependent. Approximate VCC current (ICC) can be calculated using: Initialization Once VCC exceeds the UVLO threshold and EN is HIGH, the IC checks for an open or shorted FB pin before releasing the internal soft-start ramp (SS). ICC ( mA ) = 4.58 + [( VCC − 5 + 0.013) • ( f − 128 )] 227 (1) where frequency (f) is expressed in KHz. If R1 is open (Figure 1), the error amplifier output (COMP) is forced LOW and no pulses are generated. After the SS ramp times out (T1.0), an under-voltage latched fault occurs. Setting the Output Voltage The output voltage of the regulator can be set from 0.8V to 80% of VIN by an external resistor divider (R1 and RBIAS in Figure 1). If the parallel combination of R1 and RBIAS is ≤ 1KΩ, the internal SS ramp is not released and the regulator does not start. The internal reference is 0.8V with 650nA, sourced from the FB pin to ensure that, if the pin is open, the regulator does not start. Soft-Start Once internal SS ramp has charged to 0.8V (T0.8), the output voltage is in regulation. Until SS ramp reaches 1.0V (T1.0), the “Fault Latch” is inhibited. The external resistor divider is calculated using: − 0 .8 V V 0 .8 V = OUT + 650nA RBIAS R1 To avoid skipping the soft-start cycle, it is necessary to apply VIN before VCC reaches its UVLO threshold. (2) Connect RBIAS between FB and AGND. Soft-start time is a function of oscillator frequency. FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Circuit Description Setting the Frequency EN 1.35V Oscillator frequency is determined by an external resistor, RT, connected between the R(T) pin and AGND: 2400 CLKs 0.8V f(KHz ) = FB (3) where RT is expressed in KΩ. Fault Latch Enable 1.0V 0.8V 10 6 ( 65 • R T ) + 135 R T ( KΩ ) = SS (10 6 / f ) − 135 65 (4) where frequency (f) is expressed in KHz. 3200 CLKs The regulator can not start if RT is left open. T0.8 4000 CLKs T1.0 Figure 21. Soft-Start Timing Diagram © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 www.fairchildsemi.com 10 Loop Compensation Typically the inductor is set for a ripple current (ΔIL) of 10% to 35% of the maximum DC load. Regulators requiring fast transient response use a value on the high side of this range, while regulators that require very low output ripple and/or use high-ESR capacitors restrict allowable ripple current: The loop is compensated using a feedback network around the error amplifier. Figure 22 shows a complete Type-3 compensation network. For Type-2 compensation, eliminate R3 and C3. ΔIL = VOUT • (1 - D) L•f (5) where f is the oscillator frequency and: L= VOUT • (1 - D) ΔIL • f (6) Setting the Ramp Resistor Value The internal ramp voltage excursion (ΔVRAMP) during tON should be set to 0.6V. RRAMP is approximately: RRAMP(KΩ ) ( V − 1.8) • VOUT = IN −6 −2 18 x10 • VIN • f Figure 22. Compensation Network Since the FAN2106 employs summing current-mode architecture, Type-2 compensation can be used for many applications. For applications that require wide loop bandwidth and/or use very low-ESR output capacitors, Type-3 compensation may be required. The AN-6033 spreadsheet calculator can be used to calculate these component values. (7) where frequency (f) is expressed in KHz. Setting the Current Limit Protection The FAN2106 uses its internal low-side MOSFET for current-sensing. The current-limit threshold voltage (VILIM) is compared to a scaled version of the voltage drop across the low-side MOSFET, sampled at the end of each PWM off-time/cycle. The converter output is monitored and protected against extreme overload, short-circuit, over-voltage, under-voltage, and over-temperature conditions. An internal “Fault Latch” is set for any fault intended to shut down the IC. When the fault latch is set, the IC discharges VOUT by enhancing the low-side MOSFET until FB<0.25V. The MOSFET is not turned on again unless FB>0.5V. This behavior discharges the output without causing undershoot (negative output voltage). The default threshold (ILIM open) is temperature compensated. The 10µA current sourced from the ILIM pin can be used to establish a lower, temperature–dependent, current-limit threshold by connecting an external resistor (RILIM) to AGND: RILIM(KΩ) = 0.45 • RDS • K T • (IOUT − ΔIL ) + 142.5 2 (8) 0.25/0.5V FB where: I = desired current limit set point in Amps, RDS is expressed in mΩ, KT = the normalized temperature coefficient of the low-side MOSFET (Q2) from Figure 8. PWM GATE DRIVE PWM LATCH Figure 23. Latched Fault Response Under-Voltage Shutdown After 16 consecutive, pulse-by-pulse, current-limit cycles, the fault latch is set and the regulator shuts down. Cycling VCC or EN restores operation after a normal soft-start cycle (refer to Auto-Restart section). If voltage on the FB pin remains below the undervoltage threshold for 16 consecutive clock cycles, the fault latch is set and the converter shuts down. This protection is not active until the internal SS ramp reaches 1.0V during soft start. The over-current protection fault latch is active during the soft-start cycle. In case RILIM is not connected, the IC uses internal default current limit threshold. © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 FAULT FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Calculating the Inductor Value Over-Voltage Protection / Shutdown If voltage on the FB pin exceeds the over-voltage threshold for two consecutive clock cycles, the fault latch is set and shutdown occurs. www.fairchildsemi.com 11 Over-Temperature Protection The two fault protection circuits above are active all the time, including during soft-start. The chip incorporates an over-temperature protection circuit that sets the fault latch when a die temperature of about 150°C is reached. The IC restarts when the die temperature falls below 125°C. Auto-Restart Power Good (PGOOD) Signal After a fault, EN pin is discharged by a 1µA current sink to a 1.1V threshold before the 800KΩ pull-up is restored. A new soft-start cycle begins when EN charges above 1.35V. PGOOD is an open-drain output that asserts LOW when VOUT is out of regulation, as measured at the FB pin. Thresholds are specified in the Electrical specifications section. PGOOD does not assert HIGH until the fault latch is enabled (T1.0). Depending on the external circuit, the FAN2106 can be configured to remain latched-off or to automatically restart after a fault. PCB Layout Table 1. Fault / Restart Provisioning EN pin Controller / Restart State Pull to GND OFF (disabled) VCC No restart – latched OFF(After VCC comes up) Open Immediate restart after fault Cap to GND New soft-start cycle after: tDELAY (ms) = 3.9 • C(nf) With EN left open, restart is immediate. If auto-restart is not desired, tie the EN pin to the VCC pin or pull it high after VCC comes up with a logic gate to keep the 1µA current sink from discharging EN to 1.1V. Figure 24. Figure 25. Recommended PCB Layout FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator A shorted high-side MOSFET condition is detected when SW voltage exceeds ~0.7V while the low-side MOSFET is fully enhanced. The fault latch is set immediately upon detection. Fault Latch with Delayed Auto-Restart © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 www.fairchildsemi.com 12 2X TOP VIEW 2X RECOMMENDED LAND PATTERN ALL VALUES TYPICAL EXCEPT WHERE NOTED SIDE VIEW SEATING PLANE A) DIMENSIONS ARE IN MILLIMETERS. B) DIMENSIONS AND TOLERANCES PER ASME Y14.5M, 1994 C) DIMENSIONS DO NOT INCLUDE MOLD FLASH OR BURRS. D) DESIGN BASED ON JEDEC MO-220 VARIATION WJHC E) TERMINALS ARE SYMMETRICAL AROUND THE X & Y AXIS EXCEPT WHERE DEPOPULATED. F) DRAWING FILENAME: MKT-MLP25AREV2 FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator Physical Dimensions BOTTOM VIEW Figure 26. 5x6mm Molded Leadless Package (MLP) Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products. Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings: http://www.fairchildsemi.com/packaging/ © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 www.fairchildsemi.com 13 FAN2106 — TinyBuck™ 6A, 24V Input, Integrated Synchronous Buck Regulator © 2006 Fairchild Semiconductor Corporation FAN2106 Rev. 1.0.8 www.fairchildsemi.com 14