TX4139

TX4139 2A, 75V, 200KHz Step-Down Converter FEATURES DESCRIPTION  Wide 4.5V to 75V Operating Input Range The TX4139 is a monolithic step-down switch mode converter. It achieves 2A continuous output current over a wide input supply range with excellent load and line regulation.  Output Adjustable from 0.8V to 50V The maximum peak current can be programmed by sensing current through an accurate sense resistor.  130mΩ Internal Power MOSFET Switch  Light load High Efficiency  Power Save Mode at light load  Programmable maximum peak current  91.8% Efficiency at Vin=72V，Vout=12V@1.2A  81.4% Efficiency at Vin=72V，Vout=5V@0.8A Fault condition protection includes cycle-by-cycle current limiting and thermal shutdown. The TX4139 requires a minimum number of readilyavailable standard external components. TheTX4139 is available in 8-pin ESOIC8 packages.  Fixed 200KHz Frequency  Thermal Shutdown  Cycle-by-Cycle Over Current Protection  Available in 8-Pin ESOIC8 Packages APPLICATIONS  Balance Bike  ebike  USB Power Supplies TYPICAL APPLICATION 3 C1A 10 0 µF 100V C1B VIN BS 8 R3 10Ω C3 100nF 2 R4 0.1µF 30mΩ 100V 6 ILIM TX4139 EN SW 5V/2A 1 D1 SS310 L1 33µΗ ILIM(9) POK GND 7 4 FB 5 www.xdssemi.com C2 C4 47pF R1 300K 1% 22 0 µF 16V R2 57.1K 1% TX4139_V1.1 第 1 页 ORDERING INFORMATION PART NUMBER ETEMPERATURE RANGE PACKAGE ABSOLUTE MAXIMUM RATINGS (1) Supply Voltage VIN ,VILIM ............................................................. 76V VSW .............................................................................-0.3V to VIN + 0.3V VBST............................................................................................. VSW + 6.0V VPOK ................................................................................................. 0V to 45V All Other Pins .....................................-0.3V to +6.5V Junction Temperature ..................................... 150°C Lead Temperature ........................................... 260°C Storage Temperature ...................... -65°C to +150°C TX4139 -40°C to 85°C ESOIC8 PIN CONFIGURATION (2) Recommended Operating Conditions SW 1 ILIM 2 VIN 3 GND 4 ILIM (9) 8 BS 7 POK 6 EN 5 FB Supply Voltage VIN..........................................................4.5V to 75V Output Voltage VOUT 0.8V to 40V Operating Temperature ..................... -40°C to +85°C Thermal Resistance (3) θJA θJC ESOIC8 .................................... 45 ......... 15 ... °C/W Notes: 1) Exceeding these ratings may damage the device. 2) The device is not guaranteed to function outside of its operating conditions. 3) Measured on approximately 42x45mm^2 of 1 oz copper. PIN No. PIN NAME PIN DESCRIPTION 1 2、9 SW ILIM 3 VIN 4 Gnd 5 FB 6 EN 7 POK Power good signal. When FB is less than 90% of 0.8V, PGOOD is low. It is an open-drain output. Use a high value pull-up resistor externally to pull it up to system power supply or its output as next chip enable signal. connected to Gnd or floating when don’t use this function. 8 BS Bootstrap. This pin acts as the positive rail for the high-side switch’s gate driver. Connect a 100nF ceramic cap and 10ohm resistor between this pin and SW. Switch Output. Connect this pin to the switching end of the inductor. programmable maximum peak current pin by sensing current through an accurate sense resistor between this pin and VIN. Supply Voltage. The TX4139 operates from a +4.5V to +75V unregulated input.CIN is needed to prevent large voltage spikes from appearing at the input. Put CIN as close to the IC as possible. It is the drain of the internal power device and power supply for the whole chip. Ground. This pin is the voltage reference for the regulated output voltage. For this reason care must be taken in its layout. This node should be placed outside of the D1 to CIN ground path to prevent switching current spikes from inducing voltage noise into the part. Feedback. An external resistor divider from the output to GND, tapped to the FB pin sets the output voltage. To prevent current limit run away during a short circuit fault condition the frequency-fold-back comparator lowers the oscillator frequency when the FB voltage is below 250mV. Enable pin. Connect to low off the chip,Floating is enable www.xdssemi.com TX4139_V1.1 第 2 页 ELECTRICAL CHARACTERISTICS VIN = 12V, TA = +25°C, unless otherwise noted. PARAMETER SYMBOL TEST CONDITIONS Feedback Voltage VFB 4.5V ≤ VIN ≤ 80V Feedback Bias Current IBIAS(FB) VFB = 0.8V Switch On Resistance RDS(ON) MIN 0.785 Current Limit (4) Oscillator Frequency fSW Fold-Back Frequency VFB = 0.6V VBST - VSW Minimum On Time (5) tON Main Control Loop The TX4139 is a current mode buck regulator. That is, the error amplifier (EA) output voltage is proportional to the peak inductor current. At the beginning of a cycle, the integrated high side power switch M1 is off; the EA output voltage is higher than the current sense amplifier output; and the current comparator’s output is low. The rising edge of the 200KHz clock signal sets the RS Flip-Flop. Its output turns on M1 thus connecting the SW pin and inductor to the input supply. The increasing inductor current is sensed and amplified by the Current Sense Amplifier. Ramp compensation is added to Current Sense Amplifier output and compared to the Error Amplifier output by the PWM Comparator. When the Current Sense Amplifier plus Slope Compensation signal exceeds the EA output voltage, the RS Flip-Flop is reset and the TX4139 reverts to its initial M1 off state. If the Current Sense Amplifier plus Slope Compensation signal does not exceed the COMP voltage, then the falling edge of the CLK resets the Flip-Flop. The output of the Error Amplifier integrates the voltage difference between the feedback and the 0.8V 130 mΩ 240 KHz 70 KHz 6 V 100 ns 200 OPERATION nA 200 Under Voltage Lockout Threshold Hysteresis Note: 4) sense resistor defined 5) Guaranteed by design 10 160 3.0 Thermal Shutdown (5) 0.825 V 1.5 VFB = 1V VEN = 2V, VFB = 1V 0.805 UNIT 1.35 Under Voltage Lockout Threshold Rising Supply Current (Quiescent) MAX 1.2 VFB = 0V Boot-Strap Voltage TYP 3.3 A 3.6 V mV 400 700 μA 160 °C bandgap reference. The polarity is such that a FB pin voltage lower than 0.8V increases the EA output voltage. Since the EA output voltage is proportional to the peak inductor current, an increase in its voltage increases current delivered to the output. An external Schottky Diode (D1) carries the inductor current when internal power MOS is off. APPLICATION INFORMATION Setting the Output Voltage The external resistor divider is used to set the output voltage (see the schematic on front page). The feedback resistor R1 also sets the feedback loop bandwidth with the internal compensation capacitor (see Figure 1). Choose R1 to be around 300kΩ for optimal transient response. R2 is then given by: R2 = R1 VOUT / 0.805 − 1 Table 1 –Resistor Selection for Common Vout(V) R1(K Ω) R2(KΩ) 3.3 300(1%) 96(1%) 5 300(1%) 57.1(1%) 12 300(1%) 21.4(1%) 15 300(1%) 16.9(1%) 24 300(1%) 10.2(1%) 32 300(1%) 7.6(1%) www.xdssemi.com TX4139_V1.1 第 3 页 Selecting the Inductor 33µH to 100µH inductor with a DC current rating of at least 30% percent higher than the maximum load current is recommended for most applications. For highest efficiency, the inductor DC resistance should be less than 50mΩ. For most designs, the inductance value can be derived from the following equation. L= VOUT × (VIN − VOUT ) VIN × ∆IL × ƒ sw Table 2 –Sense Resistor Selection Max. output current （A） Rsense（mΩ） 0.8 50 1.0 40 2.0 30 Loop compensation Where ΔIL is the inductor ripple current. Choose inductor current ripple to be approximately 30%-40% of the maximum load current,. The maximum inductor peak current is: ∆IL IL ( MAX ) = Iout ( MAX ) + 2 Under light load conditions below 100mA, larger inductance is recommended for improved efficiency. Selecting the Input Capacitor The input capacitor reduces the surge current drawn from the input and also the switching noise from the device. The input capacitor impedance at the switching frequency should be less than the input source impedance to prevent high frequency switching current from pass to the input. For most applications, a 47uF to 100uF electrolytic capacitor is sufficient. Selecting the Output Capacitor The output capacitor keeps output voltage small and ensures regulation loop stability. The output capacitor impedance should be low at the switching frequency. a 220uF electrolytic capacitor is recommended. ILIM sense resistor Power current flow into the chip via the external accuracy sense resistor which defined the maximum peak current. In guarantee under the normal start up with full load, the sense resistor is recommended use the larger value to ensure less surge current and output output short power dissipation. The sense resistor value should be reduced when used it at low temperature situation to ensure enough startup energy. A 12pf-82pf ceramic capacitor connected between FB and OUT can optimize the loop stability for both bandwidth and phase margin, recommended a 22-47pf ceramic capacitor in most case. PCB Layout 1) Under the large output current and high input voltage case, the schottky diode and the converter is the main heat source, don’t put them too close, the PCB layout should keep enough area for heat dissipation. Recommended ratio is 6:4 for schottky diode and the convertor，for the cost issues, the normal selection of PCB is 1oz thickness, the thick solder tin is benefit on heat dissipation. 2) ILIM is internal connected the power MOS, the heat dissipation should be considered for this pin. 3) The large current path (ILIM 、SW) should be put closer the converter as possible, use short, straight, wide copper foil connect. 4) Input capacitor should be put as close as possible to Vin and GND. 5) The loop of input capacitor, internal power MOS and schottky diode is the highest di/dt radiation region，reduce this region as possible. a 0.1uF ceramic capacitor can be used to form a small loop with internal power MOS and schottky diode, which can reduce the switch ringing caused by PCB parasitic inductor. 6) The outside feedback resistor should be placed nearby the FB pin and keep away from SW node. 7) A 220pf ceramic capacitor between VIN and SW pin can be used to reduce the switch negative overshoot and improve EMI performance when needed. www.xdssemi.com TX4139_V1.1 第 4 页 TYPICAL APPLICATION 3 C1A 10 0 µF 100V VIN 8 BS R3 10Ω C3 100nF 2 C1B ILIM R4 0.1µF 30mΩ 100V 6 TX4139 SW 5V/2A 1 L1 33µΗ D1 SS310 ILIM(9) EN POK GND 7 4 C2 C4 47pF 22 0 µF 16V R1 300K 1% FB 5 R2 57.1K 1% 5V/2A BOM LIST: Ref Value Description Package Manufacturer Qty Manufacturer P/N C1A 100uF Electrolytic,100V ELC SMD jiang hai 1 VTD-100V100 C1B 0.1uF Ceramic capacitor,100V 0603 muRata 1 GRM188R71C104K C2 220uF Electrolytic,16V ELC SMD jiang hai 1 VTD-100V220 C3 100nF Ceramic capacitor, 100V, X7R 0603 muRata 1 GRM188R71C104K C4 47pF Ceramic, capacitor 25V, X7R 0603 muRata D1 3A Schottky Diode, SMD, 100V, 3A SMB L1 33uH Inductor CDRH104, 2.4A CDRH104 R1 300KΩ Film Res., 1% 0603 Panasonic 1 ERJ-3EKF3003V R2 57.1KΩ Film Res., 1% 0603 Panasonic 1 ERJ-3EKF5712V R3 10Ω Film Res., 1% 0603 Panasonic 1 ERJ-3EKF0011V R4 30mΩ Film Res., 1% 1206 DC-DC convertor ESOP8 U1 1 GRM32DR71E470K 1 SS310 1 1 TX4139 1 Note： recommended to use a low Vf schottky diode for efficiency promotion. 95% 90% EFFICIENCY 85% 80% 75% 70% VOUT=5V VIN=12V VIN=24V VIN=36V VIN=48V VIN=60V VIN=72V 65% 60% 55% 50% 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 IOUT(A) www.xdssemi.com TX4139_V1.1 第 5 页 TYPICAL APPLICATION 3 C1A 10 0 µF 100V C1B VIN 8 BS R3 10Ω C3 100nF 2 ILIM R4 0.1µF 30mΩ 100V 6 TX4139 EN SW 12V/2A 1 L1 47µΗ D1 SS310 C2 C4 47pF ILIM(9) POK GND 7 4 R1 300K 1% FB 5 22 0 µF 25V R2 21.5K 1% 12V/2A BOM LIST: Ref Value Description Package Manufacturer Qty Manufacturer P/N C1A 100uF Electrolytic,100V ELC SMD jiang hai 1 VTD-100V100 C1B 0.1uF Ceramic capacitor,100V 0603 muRata 1 GRM188R71C104K C2 220uF Electrolytic,25V ELC SMD jiang hai 1 VTD-100V220 C3 100nF Ceramic capacitor, 100V, X7R 0603 muRata 1 GRM188R71C104K C4 47pF Ceramic, capacitor 25V, X7R 0603 muRata 1 GRM32DR71E470K D1 3A Schottky Diode, SMD, 100V, 3A SMB 1 SS310 L1 47uH Inductor CDRH127, 2.5A CDRH127 R1 300KΩ Film Res., 1% 0603 Panasonic 1 ERJ-3EKF3003V R2 21.5KΩ Film Res., 1% 0603 Panasonic 1 ERJ-3EKF2152V R3 10Ω Film Res., 1% 0603 Panasonic 1 ERJ-3EKF0011V R4 30mΩ Film Res., 1% 1206 DC-DC convertor ESOP8 U1 1 1 TX4139 1 Note： recommended to use a low Vf schottky diode for efficiency promotion. 100% 95% EFFICIENCY 90% 85% 80% VOUT=12V VIN=24V VIN=36V VIN=48V VIN=60V VIN=72V 75% 70% 65% 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 IOUT(A) www.xdssemi.com TX4139_V1.1 第 6 页 PCB LAYOUT： www.xdssemi.com TX4139_V1.1 第 7 页 PACKAGE OUTLINE ESOIC8 PACKAGE OUTLINE AND DIMENSIONS www.xdssemi.com TX4139_V1.1 第 8 页