TD1836

Techcode® DATASHEET 80V, 800MA, 480kHz Non-synchronous Buck Converter TD1836 TD8325 General Description Features The TD1836 is a monolithic, step-down, switch mode converter with a built-in power MOSFET. It achieves a 0.8A peak-output current over input supply 11V-80V with excellent load and line regulation. Current-mode operation provides a fast transient response and eases loop stabilization. Fault condition protections include cycle-by-cycle current limiting and thermal shutdown. The TD1836 requires a minimal number of readily-available external components. The TD1836 is available in a SOT23-6 package.            0.8A Peak Output Current 0.7Ω Internal Power MOSFET Stable with Low-ESR Ceramic Output Capacitors Up to 91% Efficiency 0.1μA Shutdown Mode Fixed 480kHz Frequency Thermal Shutdown Cycle-by-Cycle Over-Current Protection 11V to 80V Operating Input Range Max duty 90% Available in a SOT23-6 Package Package Type Applications      Power Meters Distributed Power Systems Battery Chargers Pre-Regulator for Linear Regulators WLED Drivers SOT23-6 Pin Configurations (Top view) May 6, 2020. Techcode Semiconductor Limited 1 www.techcodesemi.com Techcode® DATASHEET 80V, 800MA, 480kHz Non-synchronous Buck Converter TD1836 TD8325 Pin Description Pin Number 1 2 Pin Name Description BST Bootstrap. Connect a capacitor between the SW and BS pins to form a floating supply across the power switch driver. This capacitor drives the power switch’s gate above the supply voltage. GND Ground. Voltage reference for the regulated output voltage. Requires special layout considerations. Isolate this node from the D1 to C1 ground path to prevent switching current spikes from inducing. 3 FB Feedback. Sets the output voltage. Connect to the tap of an external resistor divider from the output to GND. The frequency foldback comparator lowers the oscillator frequency when the FB voltage is below 300mV to prevent current-limit runaway during a short-circuit fault. 4 EN On/Off. Pull EN above 1.35V to turn the device ON. For automatic enable, connect to VIN using a 1MΩ resistor. 5 VIN Supply Voltage. The TD1836 operates from a 11V-to-75V unregulated input. Requires C1 to prevent large voltage spikes from appearing at the input. 6 SW Power Switching Output. It is the Drain of the N-Channel power MOSFET to supply power to the output LC filter. Ordering Information TD1836 □ Circuit Type Packing: Blank：Tube R: Tape and Reel Package T：SOT23-6 May 6, 2020. □ Techcode Semiconductor Limited 2 www.techcodesemi.com Techcode® DATASHEET 80V, 800MA, 480kHz Non-synchronous Buck Converter TD1836 TD8325 Function Block Figure1 Function Block Diagram of TD1836 Absolute Maximum Ratings (Note1) Symbol Parameter Rating Unit VIN -0.3 ~ 80 V VSW VIN Supply Voltage（VIN to Gnd） SW to GND Voltage -0.3 to VIN+0.3 V VBS BS to GND Voltage VSW - 0.3 ~ VSW +6 V All Other Pins PD Power Dissipation TJ Junction Temperature TSTG Storage Temperature TSDR Maximum Lead Soldering Temperature (10 Seconds) -0.3 ~ 6 Internally Limited 150 -65 ~ 150 260 V W ºC ºC ºC Note1: Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. May 6, 2020. Techcode Semiconductor Limited 3 www.techcodesemi.com Techcode® DATASHEET 80V, 800MA, 480kHz Non-synchronous Buck Converter TD1836 TD8325 Thermal Characteristics Symbol Parameter Junction-to-Ambient Resistance in free air θJA (Note 2) SOT-23-6 Typical Value Unit 250 °C/W Note 2: θJA is measured with the component mounted on a high effective thermal conductivity test board in free air. Recommended Operation Conditions (Note3) Symbol Parameter Range Unit 11 ~ 75 V V VIN VIN Supply Voltage VOUT Converter Output Voltage VFB ~ VIN*90% Operating Junction Temp -40 ~ 125 o C Note 3: Refer to the typical application circuit Electrical Characteristics Unless otherwise specified, these specifications apply over VIN=12V, VEN=3V and TA = 25ºC. Symbol Parameter Test Conditions Min Typ 0.792 0.812 VFB Feedback Voltage 10V ≤ VIN ≤ 75V IFB Feedback Current VFB = 0.85V RDS(ON) Switch-On Resistance ISW_LKG Switch Leakage VEN=0V,VSW=0V Max Unit 0.832 V 0.1 µA - - - 0.7 - Ω - - 1 µA - 1.25 - A 380 480 580 kHZ ILIM Current Limit fSW Oscillator Frequency VFB=0.6V fSW_F Foldback Frequency VFB=0V - 120 - KHZ DMAX Maximum Duty Cycle VFB=0.6V - 90 - % TON Minimum ON-Time - 100 - ns VUVLO_R Under-Voltage Lockout Threshold, Rising - 7.5 8.5 V VUVLO_F Under-Voltage Lockout Threshold, Falling - 7.1 - V VUVLO_HYS Under-Voltage Lockout Threshold,Hysteresis - 0.4 - V EN Threshold, Rising - 1.35 - V VEN_R May 6, 2020. Techcode Semiconductor Limited 4 www.techcodesemi.com Techcode® DATASHEET 80V, 800MA, 480kHz Non-synchronous Buck Converter TD8325 VEN_F VEN_HYS TD1836 EN Threshold, Falling - 1.17 - V EN Threshold, Hysteresis - 180 - mv VEN=2V - 3.1 - µA VEN=0V - 0.1 - µA IEN EN Input Current IS Supply Current (Shutdown) VEN=0V - 0.1 1 µA IQ Supply Current (Quiescent) VEN=2V,VFB=1V - 0.73 0.85 mA TSD Thermal Shutdown - 165 - o - o TSD_HYS - Thermal Shutdown Hysteresis 20 C C Typical Application Circuit U1 5 VIN C1 10uF VIN BST SW R4 1M 1 6 C2 0.1uF L1 15uH D1 SS210 TD1836 5V VOUT C3 22uF 2 EN GND R2 68K 4 FB 3 R1 13K R3 C4 NC NC OPERATION The TD1836 is a current mode buck regulator. That is, the EA output voltage is proportional to the peak inductor current. At the beginning of a cycle, 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 480kHz CLK 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 summed to the Current Sense Amplifier output and compared to the Error Amplifier output by the PWM Comparator. When the sum of the Current Sense Amplifier output and the Slope Compensation signal exceeds the EA output voltage, the RS Flip-Flop is reset and M1 is turned off. The external Schottky rectifier diode (D1) conducts the inductor current. If the sum of the Current Sense Amplifier output and the Slope Compensation signal does not exceed the EA output for a whole cycle, 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 0.812V bandgap reference. The polarity is such that lower than 0.812V FB pin voltage increases the EA output voltage. Since the EA output voltage is proportional to the peak inductor current, an increase in its voltage also increases current delivered to the output. May 6, 2020. Techcode Semiconductor Limited 5 www.techcodesemi.com Techcode® DATASHEET 80V, 800MA, 480kHz Non-synchronous Buck Converter TD1836 TD8325 Application Information Setting Output Voltage The external resistor divider sets the output voltage (see the Typical Application schematic). Table 1 lists resistors for common output voltages. The feedback resistor (R2) also sets the feedback loop bandwidth with the internal compensation capacitor (see Figure 1). R1 is: R1 = R2 V −1 0.812V Table 1:Resistor Selection for Common output voltages VOUT(V) 1.8 R1(KΩ) 102(1%) R2(KΩ) 124(1%) 2.5 59(1%) 124(1%) 3.3 40.2(1%) 124(1%) 5 23.7(1%) 124(1%) Selecting the Inductor Use an inductor with a DC current rating at least 25% percent higher than the maximum load current for most applications. For best efficiency, the inductor’s DC resistance should be less than 200mΩ. For most designs, the required inductance value can be derived from the following equation. V × (V − V ) L= V × ∆I × f Where ΔIL is the inductor ripple current. Choose the inductor ripple current to be 30% of the maximum load current. The maximum inductor peak current is: high-frequency-switching current from passing through the input. Use ceramic capacitors with X5R or X7R dielectrics for their low ESRs and small temperature coefficients. For most applications, a 4.7μF capacitor will sufficient. Selecting the Output Capacitor The output capacitor keeps the output voltage ripple small and ensures feedback loop stability. The output capacitor impedance should be low at the switching frequency. Use ceramic capacitors with X5R or X7R dielectrics for their low ESR characteristics. For most applications, a 22μF ceramic capacitor will sufficient. PCB Layout Guide PCB layout is very important to stability. Please follow these guidelines and use Figure 2 as reference. 1) Keep the path of switching current short and minimize the loop area formed by the input capacitor, high-side MOSFET, and Schottky diode. 2) Keep the connection from the power ground→Schottky diode→SW pin as short and wide as possible. 3) Ensure all feedback connections are short and direct. Place the feedback resistors and compensation components as close to the chip as possible. 4) Route SW away from sensitive analog areas such as FB. 5) Connect IN, SW, and especially GND to large copper areas to cool the chip for improved thermal performance and long- term reliability. For single layer PCBs, avoid soldering the exposed pad. ∆I 2 Under light-load conditions (below 100mA), use a larger inductance to improve efficiency. I ( ) =I + Selecting the Input Capacitor The input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. The input capacitor impedance at the switching frequency should be less than the input source impedance to prevent May 6, 2020. Techcode Semiconductor Limited 6 Figure 2: PCB Layout www.techcodesemi.com Techcode® DATASHEET 80V, 800MA, 480kHz Non-synchronous Buck Converter TD1836 TD8325 Package Information SOT23-6 Package Outline Dimensions May 6, 2020. Techcode Semiconductor Limited 7 www.techcodesemi.com Techcode® DATASHEET 80V, 800MA, 480kHz Non-synchronous Buck Converter TD1836 TD8325 Design Notes May 6, 2020. Techcode Semiconductor Limited 8 www.techcodesemi.com