ZTP7192T

ZTP7192T 2A, 18V, 500KHz, Synchronous Step-Down DC/DC Converter FEATURES DESCRIPTION ● 4.5V to 18V input voltage The ZTP7192T is a high-frequency, synchronous, rectified, step-down, switch-mode converter with internal power MOSFETs. It offers a very compact solution to achieve a 2A continuous output current over a wide input supply range, with excellent load and line regulation. The ZTP7192T has synchronous-mode operation for higher efficiency over the output current-load range. Current-mode operation provides fast transient response and eases loop stabilization. Protection features include over-current protection and thermal shutdown. The ZTP7192T requires a minimal number of readily available, standard external components and is available in space-saving TSOT23-6L package. ● Output adjustable from 0.8V to 15V ● Output current up to 2A ● Integrated 140mΩ/90mΩ power MOSFET switches ● Shutdown current 3μA typical ● Efficiency up to 95% ● Fixed frequency 500KHz ● Internal soft start ● Over current protection and Hiccup ● Over temperature protection ● RoHS Compliant and 100% Lead (Pb) Free APPLICATIONS ● Distributed power systems ● Networking systems ● FPGA, DSP, ASIC power supplies Pins Configuration ● Notebook computers ● Green electronics or appliance Top View TSOT23-6L ORDERING INFORMATION GND 1 PART PACKAGE RoHS Ship, Quantity ZTP7192T TSOT23-6L Yes Tape and Reel 6 BOOT SW 2 5 EN IN 3 4 FB Typical Application Circuit Input C1 10μF/25V Ceramic R4 100k R5 5 C7 0.1μF 3 IN EN C5 100nF 6 BOOT SW 2 ZTP7192T FB 4 RT(opt) L1 4.7μH Output 3.3V/2A R1 47K GND 1 Cff* R2 15K C2 10μF/6.3V Ceramic x 2 Note1: R5 and C7 are optional. Note2: Cff are optional.Users can adjust the Cff value according to their bandwidth requirements. Details please see the DVT report. DS-17 Copyright © ZillTek Technology Corp. - 1- 4F-3, No.5, Technology Rd., Science-Based Industrial Park, Hsinchu 30078, Taiwan Tel: (886) 3577 7509; Fax: (886) 3577 7390 Email: sales@zilltek.com ZTP7192T Absolute Maximum Ratings Recommended Operating Conditions Supply Voltage V IN ……...…………...…….…………. 4.5V to 18V Output Voltage VOUT ……...…………...…….….. 0.8V to VIN–3V Operating Temperature Range ……...…… –40°C to +125°C Supply Voltage VIN ……………………………….... –0.3 V to +19V Enable Voltage VEN …………………………….... –0.3 V to VINV Switch Node VSW ………………………………. –0 .3V to VIN+0.3V -0.3V(-5V for 3.3V, Load=2A) Output Ripple (12V => 3.3V, Load=2A) Output Ripple (12V => 3.3V, Load=1A) Output Ripple (12V => 3.3V, Load=0A) Dynamic Load (Iload=0.5A_2A Vout=3.3V) Short Circuit Protection Efficiency DS-17 Copyright © ZillTek Technology Corp. - 4- 4F-3, No.5, Technology Rd., Science-Based Industrial Park, Hsinchu 30078, Taiwan Tel: (886) 3577 7509; Fax: (886) 3577 7390 Email: sales@zilltek.com ZTP7192T Line regulation Load regulation Temperature Rise vs Load Current(Vo=5V,L=6.8uH) DS-17 Copyright © ZillTek Technology Corp. - 5- 4F-3, No.5, Technology Rd., Science-Based Industrial Park, Hsinchu 30078, Taiwan Tel: (886) 3577 7509; Fax: (886) 3577 7390 Email: sales@zilltek.com ZTP7192T APPLICATION INFORMATION FB: Feedback Input. FB senses the output voltage to regulate that voltage. Drive FB with a resistive voltage divider from the output voltage. The feedback threshold is 0.8V. Overview The ZTP7192T is a synchronous rectified, current-mode, step-down r egulator. It regulates input voltages from 4.5V to 18V down to an output voltage as low as 0.8V, and supplies up to 2A of load current. The ZTP7192T uses current-mode control to r egulate the output voltage. The output voltage is measured at FB through a resistive voltage divider and amplified through the internal trans-conductance error amplifier. The converter uses internal N-Channel MOSFET switches to step-down the input voltage to the r egulated output voltage. Since the high side MOSFET r equires a gate voltage greater than the input voltage, a boost capacitor connected between SW and BOOT is needed to drive the high side gate. The boost capacitor is charged from the internal 5V rail when SW is low. The ZTP7192T has power save mode for light load. During this time, the internal clock is blocked,thus the ZTP7192T skips some pulses for PFM(Pulse Frequency Modulation) mode and achieves the light load power save. When the ZTP7192T FB pin exceeds 20% of the nominal regulation voltage of 0.8V, the over voltage comparator is tripped, forcing the high-side switch off. EN: Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the regulator, drive it low to turn it off. Pull up with 100kΩ resistor for automatic startup. Setting the Output Voltage The external resistor divider sets the output voltage. The feedback resistor R1 also sets the feedback-loop bandwidth through the internal compensation capacitor (see the Typical Application circuit). Choose R1 around 10kΩ, and R2 by: R2 = R1 / (VOUT/0.8V – 1) Use a network below for when VOUT is low. FB RT R1 VOUT R2 Figure 1: Network. Table 1 lists the recommended T-type resistors value for common output voltages.(RT=0) Pins Description BOOT: High-Side Gate Drive Boost Input. BOOT supplies the drive for the high-side N-Channel MOSFET switch. Connect a 0.1μF or greater capacitor from SW to BOOT to power the high side switch. VOUT (V) 1.05 R1 (KΩ) 103.8(1%) R2 (KΩ) 332.1(1%) Rt (Ω) 0(1%) 1.2 1.8 2.5 100(1%) 85(1%) 67.5(1%) 200.1(1%) 68(1%) 31.8(1%) 0(1%) 0(1%) 0(1%) IN: Power Input. IN supplies the power to the IC, as well as the step-down converter switches. Drive IN with a 4.5V to 18V power source. Bypass IN to GND with a suitably large capacitor to eliminate noise on the input to the IC. 3.3 5 47.5(1%) 83.1(1%) 15.2(1%) 15.8(1%) 0(1%) 0(1%) Table 1: Resistor selection for common output voltages. Rt is used to set control loop’s bandwidth, which is proportional to the relation by R1, R2, RT: 1/[(Rt+20k)*(1+R1/R2)+R1] So Increase RT & Decrease R1&R2 value(keeping R1/R2 ratio), the bandwi dth can be kept the same(the relation value need to be the same) SW: Power Switching Output. SW is the switching node that supplies power to the output. Connect the output LC filter from SW to the output load. Note that a capacitor is required from SW to BOOT to power the high-side switch. GND: Ground. DS-17 Copyright © ZillTek Technology Corp. - 6- 4F-3, No.5, Technology Rd., Science-Based Industrial Park, Hsinchu 30078, Taiwan Tel: (886) 3577 7509; Fax: (886) 3577 7390 Email: sales@zilltek.com ZTP7192T supply the AC current to the step-down converter while maintaining the DC input voltage. Use low ESR capacitors for the best performance. Ceramic capacitors are preferred, but tantalum or low-ESR electrolytic capacitors may also suffice. Choose X5R or X7R dielectrics when using ceramic capacitors. Since the input capacitor (C1) absorbs the input switching current it requires an adequate ripple current rating. The RMS current in the input capacitor can be estimated by: Inductor The inductor is required to supply constant current to the output load while being driven by the switched input voltage. A larger value inductor will result in less ripple current that will result in lower output ripple voltage. However, the larger value inductor will have a larger physical size, higher series resistance, and/or lower saturation current. A good rule for determining the inductance to use is to allow the peak-to-peak ripple current in the inductor to be approximately 30% of the maximum switch current limit. Also, make sure that the peak inductor current is below the maximum switch current limit. The inductance value can be calculated by: I C1 = I LOAD × [ (VOUT/VIN) × (1 − VOUT/VIN) ]1/2 L = [ VOUT / (fS × ΔI L) ] × (1 − VOUT/VIN) Where VOUT is the output voltage, VIN is the input voltage, fS is the switching frequency, and ΔI L is the peak-to-peak inductor ripple current. Choose an inductor that will not saturate under the maximum inductor peak current. The p eak inductor current can be calculated by: I LP = I LOAD + [ VOUT / (2 × fS × L) ] × (1 − VOUT/VIN) Where I LOAD is the load current. The choice of which style inductor to use mainly depends on the price vs. size requirements and any EMI requirements. ΔVIN = [ I LOAD /(C1 × fS) ] × (VOUT/VIN) × (1 − VOUT/VIN) Where C1 is the input capacitance value. Output Capacitor Optional Schottky Diode The output capacitor is required to maintain the DC output voltage. Ceramic, tantalum, or low ESR electrolytic capacitors are recommended. Low ESR capacitors are preferred to keep the output voltage ripple low. The output voltage ripple can be estimated by: During the transition between high-side switch and low-side switch, the body diode of the low-side power MOSFET conducts the inductor current. The forward voltage of this body diode is high. An optional Schottky diode may be paralleled between the SW pin and GND pin to improve overall efficiency. Table 2 lists example Schottky diodes and their Manufacturers. Part Number B130 SK13 Voltage and Current Rating 30V, 1A 30V, 1A Diodes Inc. Diodes Inc. MBRS130 30V, 1A International Rectifier ΔVOUT = [ VOUT/(fS × L) ] × (1 − VOUT/VIN) × [ RESR + 1 / (8 × fS × C2) ] Where C2 is the output capacitance value and RESR is the equivalent series resistance (ESR) value of the output capacitor. In the case of ceramic capacitors, the impedance at the switching frequency is dominated by the capacitance. The output voltage ripple is mainly caused by the capacitance. For simplification, the output voltage ripple can be estimated by: Vendor Table 2: Diode selection guide. Input Capacitor ΔVOUT = [ VOUT/(8 × fS2 × L × C2) ] × (1 − VOUT/VIN) In the case of tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching The input current to the step-down converter is discontinuous, therefore a capacitor is required to DS-17 Copyright © ZillTek Technology Corp. The worst-case condition occurs at VIN = 2VOUT, where I C1 = I LOAD /2. For simplification, choose the input capacitor whose RMS current rating greater than half of the maximum load current. The input capacitor can be electrolytic, tantalum or ceramic. When using electrolytic or tantalum capacitors, a small, high quality ceramic capacitor, i.e. 0.1μF, should be placed as close to the IC as possible. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. The input voltage ripple for low ESR capacitors can be estimated by: - 7- 4F-3, No.5, Technology Rd., Science-Based Industrial Park, Hsinchu 30078, Taiwan Tel: (886) 3577 7509; Fax: (886) 3577 7390 Email: sales@zilltek.com ZTP7192T frequency. For simplification, the output ripple can be approximated to: minimize the loop area formed by Input capacitor, high-side MOSFET and low-side MOSFET. 2) Bypass ceramic capacitors are suggested to be put close to the VIN Pin. 3) Ensure all feedback connections are short and direct. Place the feedback resistors and compensation components as close to the chip as possible. 4) Rout SW away from sensitive analog areas such as FB. 5) Connect IN, SW, and especially GND respectively to a large copper area to cool the chip to improve thermal performance and long-term reliability. 6) It is recommended to reserve a place for Cff in layout. ΔVOUT = [ VOUT/(fS × L) ] × (1 − VOUT/VIN) × RESR The characteristics of the output capacitor also affect the stability of the regulation system. The ZTP7192T can be optimized for a wide range of capacitance and ESR values. External Bootstrap Diode An external bootstrap diode may enhance the efficiency of the regulator, the applicable conditions of external BOOT diode are: ● VOUT = 5V or 3.3V; and ● Duty cycle is high: D = VOUT/VIN > 65% In these cases, an external BOOT diode is recommended from the output of the voltage regulator to BOOT pin, as shown in Figure 2. BOM of ZTP7192T Please refer to the Typical Application Circuit. External BOOT Diode IN4148 BOOT CBS 0.1~1μF ZTP7192T SW L COUT + 5V or 3.3V Item 1 2 Reference C1 C5 Part 10μF 100nF 3 4 C7 R4 0.1μF 100K Table 3: BOM selection table I. Figure 2: Add optional external bootstrap diode to enhance efficiency. The r ecommended external BOOT diode is IN4148, and the BOOT capacitor is 0.1 ~ 1μF. When VIN ≤ 6V, for the purpose of promote the efficiency, it can add an external Schottky diode between IN and BOOT pins, as shown in Figure 3. Schottky (B0520LW) 5V to 6V L1 6.8μH R1 83.1K R2 15.8K C2 10μF×2 Vout = 3.3V Vout = 2.5V 4.7μH 3.3μH 47.5K 67.5K 15.2K 31.8K 10μF×2 10μF×2 Vout = 1.8V Vout = 1.2V 2.2μH 2.2μH 85K 100K 68K 200.1K 10μF×2 10μF×2 Table 4: BOM selection table II.(RT=0oHm) FB BOOT IN ZTP7192T SW Vout = 5.0V VOUT RT R1 VOUT R2 GND Figure 4: Structure of the feedback circuit. Figure 3: Add a Schottky diode to promote efficiency when VIN ≤ 6V. PCB Layout Guide PCB layout is very important to achieve stable operation. Please follow the guidelines below. 1) Keep the path of switching current short and DS-17 Copyright © ZillTek Technology Corp. - 8- 4F-3, No.5, Technology Rd., Science-Based Industrial Park, Hsinchu 30078, Taiwan Tel: (886) 3577 7509; Fax: (886) 3577 7390 Email: sales@zilltek.com ZTP7192T VOUT R2(MAX) R2(MIN) R1(MAX) R1(MIN) 5V 500K 2K 2.5M 10K 3.3V 500K 2K 1.5M 6K 2.5V 500K 2K 1M 4K 1.8V 500K 2K 625k 2.5K 1.5V 500K 2K 438K 1.75K 1.2V 500K 2K 250K 1K 1V 500K 2K 125K 0.5K Table 5: Feedback application range. Input Capacitance: Cin, minimum application range at least is 10 μF. Output Capacitance: Cout, minimum application range is 10μF to 100μF PACKAGE DIMENSION TSOT23-6L D C B e b A H A1 L Dimensions in mm Min Max 1.100 1.300 Dimensions in Inch Min Max 0.043 0.066 A1 B b 0.000 1.600 0.350 0.100 1.700 0.500 0.000 0.063 0.014 0.004 0.067 0.020 C D 2.650 2.820 2.950 3.020 0.104 0.111 0.116 0.119 e H L 0.950 BSC 0.080 0.200 0.300 0.600 Symbol A DS-17 Copyright © ZillTek Technology Corp. 0.037 BSC 0.003 0.008 0.012 0.024 - 9- 4F-3, No.5, Technology Rd., Science-Based Industrial Park, Hsinchu 30078, Taiwan Tel: (886) 3577 7509; Fax: (886) 3577 7390 Email: sales@zilltek.com