ZTP7192S

ZTP7192S 2A, 18V, 500KHz, Synchronous Step-Down DC/DC Converter FEATURES ● ● ● ● ● ● ● ● ● ● ● DESCRIPTION 4.75V to 18V input voltage Output adjustable from 0.923V to 15V Output current up to 2A Integrated 135mΩ/100mΩ 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 The ZTP7192S 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 ZTP7192S 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 ZTP7192S requires a minimal number of readily available, standard external components and is available in space-saving SOP-8L packages. APPLICATIONS Distributed power systems Networking systems ● FPGA, DSP, ASIC power supplies ● Notebook computers ● Green electronics or appliance ● ● Pins Configuration Top View SOP-8L ORDERING INFORMATION PART PACKAGE RoHS Ship, Quantity ZTP7192S SOP-8L Yes Tape and Reel, 3000 BOOT 1 8 NC IN 2 7 EN SW 3 6 NC GND 4 5 FB Typical Application Circuit Input C1 10μF/25V Ceramic R4 100k R5 7 C7 0.1μF 2 IN EN C5 100nF 1 BOOT SW 3 ZTP7192S L1 4.7μH Output 3.3V/2A C8 Option FB 5 GND 4 R1 25.7kΩ R2 10kΩ 1% 1% C2 10μF/6.3V Ceramic x 2 Note: R5 and C7 are optional. Details please see the DVT report. DS-10 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 ZTP7192S Absolute Maximum Ratings Recommended Operating Conditions Supply Voltage VIN ……...…………...…….……… 4.75V to 18V Output Voltage VOUT ……...…………...…….. 0.923V to VIN–3V Operating Temperature Range ……...…… –40°C to +125°C Supply Voltage VIN ……………………………….... –0.3V to +20V Switch Node VSW ………………………………. –0.3V to VIN+0.3V Boost VBOOT …………………………………… VSW–0.3V to VSW+6V All Other Pins …………………………………………… –0.3V to +6V Junction Temperature ………………………………………. +150°C Lead Temperature …………………………………………….. +260°C Storage Temperature Range …………....... –65°C to +150°C Package Thermal Characteristics SOP-8L: Thermal Resistance, θJA ……………………………………. 90°C/W Thermal Resistance, θJC ……………………………………. 45°C/W CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Pins Description SOP-8L Symbol Description 1 BOOT High-side gate drive boost input. 2 IN Power input. 3 SW Power switching output. 4 GND Ground. 5 FB Feedback input. 6 NC Not connected. 7 EN Enable input. 8 NC Not connected. Electro-Static Discharge Sensitivity This integrated circuit can be damaged by ESD. It is recommended that all integrated circuits be handled with proper precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Functional Block Diagram + _ OVP RAMP Oscillator Fosc1 or Fosc2 CLK 1.01V FB 5 + _ 2 IN Current Sense Amplifier + Σ 5V _ 1 BOOT 0.3V M1 S Q Soft Start 0.923V − + + Error Amplifier + _ Current Comparator 200K 3 SW R Q M2 0.9pF 50pF 4 GND OVP EN IN 3.3V, Load=2A) Output Ripple (12V => 3.3V, Load=1A) Output Ripple (12V => 3.3V, Load=0A) Dynamic Load (Iload=0.2A_2AVout=3.3V) Short Circuit Protection DS-10 Copyright © ZillTek Technology Corp. Efficiency -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 ZTP7192S APPLICATION INFORMATION 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. Overview The ZTP7192S is a synchronous rectified, current-mode, step-down regulator. It regulates input voltages from 4.75V to 18V down to an output voltage as low as 0.923V, and supplies up to 2A of load current. The ZTP7192S uses current-mode control to regulate the output voltage. The output voltage is measured at FB through a resistive voltage divider and amplified through the internal transconductance error amplifier. The converter uses internal N-Channel MOSFET switches to step-down the input voltage to the regulated output voltage. Since the high side MOSFET requires 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. When the ZTP7192S FB pin exceeds 10% of the nominal regulation voltage of 0.923V, the over voltage comparator is tripped, forcing the high-side switch off. Setting the Output Voltage The output voltage is set using a resistive voltage divider from the output voltage to FB pin. The voltage divider divides the output voltage down to the feedback voltage by the ratio: VFB = VOUT × R2 / (R1 + R2) Where VFB is the feedback voltage and VOUT is the output voltage. Thus the output voltage is: VOUT = 0.923 × (R1 + R2) / R2 R2 can be as high as 100kΩ, but a typical value is 10kΩ. Using the typical value for R2, R1 is determined by: R1 = 10.83 × (VOUT − 0.923V) (KΩ) Inductor Pins Description 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: 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. IN: Power Input. IN supplies the power to the IC, as well as the step-down converter switches. Drive IN with a 4.75V to 18V power source. Bypass IN to GND with a suitably large capacitor to eliminate noise on the input to the IC. L = [ VOUT / (fS × ΔIL) ] × (1 − VOUT/VIN) 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. Where VOUT is the output voltage, VIN is the input voltage, fS is the switching frequency, and ΔIL is the peak-to-peak inductor ripple current. Choose an inductor that will not saturate under the maximum inductor peak current. The peak inductor current can be calculated by: GND: Ground. ILP = ILOAD + [ VOUT / (2 × fS × L) ] × (1 − VOUT/VIN) 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 0.923V. DS-10 Copyright © ZillTek Technology Corp. Where ILOAD is the load current. The choice of which style inductor to use mainly depends on the price vs. size requirements and any EMI requirements. -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 ZTP7192S 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 1 lists example Schottky diodes and their Manufacturers. Part Number B130 SK13 MBRS130 Voltage and Current Rating 30V, 1A 30V, 1A 30V, 1A 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 Diodes Inc. Diodes Inc. International Rectifier Table 1: Diode selection guide. Input Capacitor 2 ΔVOUT = [ VOUT/(8 × fS × L × C2) ] × (1 − VOUT/VIN) In the case of tantalum or electrolytic capacitors, the ESR dominates the impedance at the switching frequency. For simplification, the output ripple can be approximated to: The input current to the step-down converter is discontinuous, therefore a capacitor is required to 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: IC1 = ILOAD × [ (VOUT/VIN) × (1 − VOUT/VIN) ] ΔVOUT = [ VOUT/(fS × L) ] × (1 − VOUT/VIN) × RESR The characteristics of the output capacitor also affect the stability of the regulation system. The ZTP7192S 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% 1/2 The worst-case condition occurs at VIN = 2VOUT, where IC1 = ILOAD/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: BOOT ZTP7192S SW External BOOT Diode IN4148 CBS 0.1~1μF L COUT + 5V or 3.3V Figure 1: Add optional external bootstrap diode to enhance efficiency. ΔVIN = [ ILOAD/(C1 × fS) ] × (VOUT/VIN) × (1 − VOUT/VIN) Where C1 is the input capacitance value. In these cases, an external BOOT diode is recommended DS-10 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 ZTP7192S from the output of the voltage regulator to BOOT pin, as shown in Figure 1. The recommended 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 2. Schottky (B0520LW) 5V to 6V 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. BOOT VOUT IN ZTP7192S SW GND BOM of ZTP7192S Please refer to the Typical Application Circuit. Figure 2: Add a Schottky diode to promote efficiency when VIN ≤ 6V. Item 1 2 3 4 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 minimize the loop area formed by Input capacitor, Vout = 5.0V Vout = 3.3V Vout = 2.5V Vout = 1.8V Vout = 1.2V Vout = 1.0V L1 6.8μH 4.7μH 4.7μH 3.3μH 2.2μH 2.2μH R1 44.2K 25.7K 17.1K 9.50K 3.00K 0.834K R2 10K 10K 10K 10K 10K 10K Reference C1 C5 C7 R4 Part 10μF 100nF 0.1μF 100K Table 2: BOM selection table I. C2 10μF×2 10μF×2 10μF×2 10μF×2 10μF×2 10μF×2 C8 100pF 100pF 50pF 50pF 20pF 20pF Table 3: BOM selection table II. DS-10 Copyright © ZillTek Technology Corp. -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 ZTP7192S PACKAGE DIMENSIONS SOP-8L E C e b D A2 A θ A1 SYMBOLS DIMENSION (MM) H L DIMENSION (INCH) MIN MAX MIN MAX A 1.300 1.752 0.051 0.069 A1 0.000 0.203 0.000 0.008 A2 1.350 1.550 0.053 0.061 b 0.330 0.510 0.013 0.020 C 5.790 6.200 0.228 0.244 D 4.700 5.110 0.185 0.201 E 3.800 4.000 0.150 0.157 e 1.270 BSC 0.050 BSC H 0.170 0.254 0.007 0.010 L 0.400 1.270 0.016 0.050 θ 0° 8° 0° 8° DS-10 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