DIO61845ST6

Rev 1.2 DIO61845 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters Features Descriptions  Operating Input Range: 5V to 40V The DIO61845 is a high-frequency, step-down,  Adjustable Output Range: 0.8V to 0.95∙VIN switching regulator with integrated high-side and  Operating Quiescent Current: 150μA low-side power MOSFET designed specifically for  Fixed Switching Frequency: 2MHz power meter applications. The DIO61845 can  400mΩ/200mΩ Internal Power MOSFETs provide up to 0.6A output current and current  Optimized for Power Meter Applications mode control for fast loop response.  Satisfies 0.1% Output Voltage Ripple The wide input range of 5V to 40V is suitable for Requirements in Power Meter Applications various power meter step-down applications.  Low Dropout Mode Quiescent current of 10μA shutdown mode allows  Light-Load Mode devices to be used for battery power supply  >90% Efficiency applications. The DIO61845 uses high duty cycle  Dedicated Internal Compensation and low dropout mode under the condition of low  Stable with Ceramic/Electrolytic Output input voltage of power meter. Capacitors The DIO61845 achieves high power conversion  Internal Soft Start (SS) efficiency in a wide load range by reducing  Precision Current Limit without Current switching frequency under light load conditions to Sensing Resistor reduce switching and gate drive losses.  Guaranteed Industrial Temperature Range Frequency folding prevents short circuit and Limits inductance current from losing control during  Package: SOT23-6 startup. Thermal shutdown provides reliable and fault-tolerant Applications operation. The DIO61845 is packaged in SOT23-6. Power Meters Only  Typical Application C3 0.1μF C3 BST SW 22μH C4 VIN C2 R3 100kΩ FB 107kΩ 1.5MΩ R2 R1 C 0.1μF C5 + 470μF GND C1 10μF VIN BST SW GND VIN FB EN 4. 7μF 10μH C2 R3 100kΩ EN Pow er Meter 12V Output Rail, 0.6A Load VOUT 5V/0.6A L1 C6 0.1μ F Opt. www.dioo.com 0.1μF VOUT 12V/0.6A L1 10.7kΩ 0.1μF C5 10μF C1 C6 0.1μF VIN 4.7μ F 56kΩ R2 R1 C Opt. Pow er Meter 5V Output Rail, 0.6A Load © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 DIO61845 Order Part Top Marking Number DIO61845ST6 DAYW TA Green Package -40 to 85°C SOT23-6 Tape & Reel, 3000 Pin Assignment SOT23-6 BST 1 6 SW GND 2 5 VIN FB 3 4 EN Figure 1 Top View Pin Descriptions Pin Name BST GND Description Bootstrap. Positive power supply for the internal, floating, high-side MOSFET driver. Connect a bypass capacitor between BST and SW. Ground. Connect an output capacitor as close to GND as possible. Avoid routing GND near high-current switch paths. Feedback. FB is the input to the error amplifier. Connect FB to an external resistor FB divider between the output and GND. Compare FB against the internal 0.8V reference to set the regulation voltage. EN Enable input. Pull EN below the specified threshold to shut the chip down. Pull EN above the specified threshold to enable the chip. Float EN to disable the chip. Input supply. VIN supplies power to the internal control circuitry, both BST regulators, VIN and the high-side switch. Place a decoupling capacitor to ground close to VIN to reduce switching spikes. SW www.dioo.com Switch node. SW is the output of the high-side switch. © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters Ordering Information DIO61845 Stresses beyond those listed under “Absolute Maximum Rating” may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other condition beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Parameter Rating Unit Supply voltage VIN -0.3 to 42 V Switch voltage VSW -0.3 to (VIN + 0.3) V BST to SW -0.3 to 6.0 V All other pins -0.3 to 6.0 V Continuous power dissipation (TA = 25°C) (1) 0.6 W Junction temperature 150 °C Lead temperature 260 °C -65 to 150 °C Storage temperature ӨJA 170 ӨJC 130 Human Body Mode 1500 V 300 mA Package Thermal Resistance ESD °C/W Latch up Note: 1. The maximum allowable power dissipation is a function of the maximum junction temperature TJ(MAX), the junction-to-ambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD(MAX)=(TJ(MAX)-TA)/θJA. Exceeding the maximum allowable power dissipation produces an excessive die temperature, and the regulator goes into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. Recommend 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. DIOO does not Recommend exceeding them or designing to Absolute Maximum Ratings. Parameter Rating Unit Supply voltage VIN 5 to 40 V Output voltage VOUT Adjustable from 0.8 V Operating junction temperature TJ -40 to 125 °C www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters Absolute Maximum Ratings DIO61845 VIN = 24V, VEN = 2V, TJ = -40°C to 125°C (2), unless otherwise noted. Typical values at TJ = 25°C. Symbol VFB Parameter Conditions Min. Typ. Max. TJ = -40°C to 125°C 0.78 0.8 0.82 TJ = 25°C 0.788 0.8 0.812 Feedback voltage V Feedback bias current RON_HS High-side switch on resistance RON_LS Low-side switch on resistance High-side switch leakage VBST - VSW = 5V 0.1 μA 400 800 mΩ 200 400 mΩ 1 μA 1 μA VEN = 0V, VSW = 0V Low-side switch leakage ILIM Unit Current limit 0.8 1.0 1.2 A VIN UVLO rising threshold 4.35 4.6 4.85 V VIN UVLO falling threshold 3.65 3.9 4.15 V VIN UVLO hysteresis Soft-start time 0.7 VFB from 10% to 90% 0.5 1 ms 2 2.4 MHz fSW Oscillator frequency tON Minimum switch on time (3) IS Shutdown supply current VEN < 0.3V 10 15 μA IQ Quiescent supply current No load, VFB = 0.83V, no switching 150 350 µA VIH 1.6 V 100 ns Thermal shutdown (3) 175 °C Thermal shutdown hysteresis (3) 30 °C Enable rising threshold Low to high Enable falling threshold Enable threshold hysteresis 1.62 1.8 1.98 V 1.395 1.55 1.705 V 250 mV Note: 2. Not tested in production and guaranteed by over-temperature correlation. 3. Not tested in production and derived from bench characterization. www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters Electrical Characteristics DIO61845 VIN 1.7MΩ EN INTERNAL REGULA TO R REFERENCE UVLO V CC 7.5V BST 0.5ms SS SS CLK Oscillator ISW 3.2pF Control Log ic ISW SW V CC 50pF 850k Ω 100kΩ FB SS 0.8 V Comp GND OPERATION The DIO61845 is a 2MHz, synchronous, step- down, switching regulator with integrated high-side and low-side power MOSFETs. The DIO61845 provides an internally compensated, highly efficient output of up to 0.6A with current- mode control and also features a wide input voltage range, internal soft-start control, and a precision current limit. Its very low operational quiescent current makes it suitable for battery-powered applications. Pulse-Width Modulation (PWM) Control At moderate-to-high output currents, the DIO61845 operates in a fixed-frequency, peak-current-control mode to regulate the output voltage. A pulse-width modulation (PWM) cycle initiated by the internal clock turns on the power high-side MOSFET (HS-FET). The HS-FET remains on until its current reaches the value set by the COMP voltage (VCOMP). After the HS-FET is off, the low-side MOSFET (LS-FET) turns on, and the inductor current flows through the LS-FET. To avoid a shoot-though, a dead time is inserted to prevent the HS-FET and LS-FET from turning on at the same time. For each turn- on and turn-off in a switching cycle, the HS-FET turns on and off with a minimum on and off time limit. To prevent inductor current and output voltage runaway, the switching frequency folds back when the HS-FET minimum turn-on is detected internally. When the PWM signal goes low, the HS-FET turns off and remains off for at least 100ns before the next cycle begins. If the current in the HS-FET does not reach the COMP-set current value within one PWM cycle, the HSFET remains on to avoid a turn-off operation. Pulse-Skipping Mode (PSM) Under light-load conditions, the DIO61845 enters pulse-skipping mode (PSM) to improve efficiency. PSM is triggered when VCOMP drops below the internal sleep threshold, which generates a pause command to block the turn- on clock pulse, so the power MOSFET does not turn on. This reduces gate driving and switching losses. www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters Block Diagram DIO61845 load efficiency. When VCOMP exceeds the sleep threshold, the pause signal resets, and the chip resumes normal PWM operation. Whenever the pause command changes from low to high, the PWM signal goes high immediately and turns on the power MOSFET. Error Amplifier (EA) The error amplifier is composed of an internal op-amp with an R-C feedback network connected between its output node (internal COMP node) and its negative input node (FB). When the FB voltage (VFB) drops below the internal reference voltage (VREF), the op-amp drives the COMP output high, producing a higher switch peak current output and delivering more energy to the output. Conversely, when VFB rises above VREF, the switch peak current output drops. Connect FB to the tap of a voltage divider connected between VOUT and GND composed of R1 and R2. R1 also serves to control the gain of the error amplifier in addition to the internal compensation R-C network. Internal Regulator The 2.6V internal regulator powers most of the internal circuitry. This regulator takes the VIN input and operates in the full VIN range. When VIN is greater than 3.0V, the output of the regulator is in full regulation. When VIN drops below 3.0V, the output degrades. Enable Control (EN) The DIO61845 has a dedicated enable control pin (EN). When VIN rises above the threshold, EN can enable or disable the chip for high effective logic. Its falling threshold is 1.55V, and its rising threshold is about 1.8V. An internal 1.7MΩ resistor from EN to GND allows EN to be floated to shut down the chip. When the EN voltage is pulled to 0V, the chip enters the lowest shutdown current mode. When the EN voltage rises above 0V but remains below the rising threshold, the chip remains in shutdown mode with a slightly higher shutdown current. EN is clamped internally using a 7.5V series Zener diode. Connecting the EN input through a pull-up resistor to VIN limits the EN input current below 100μA. For example, with 12V connected to VIN, RPULLUP≥(12V7.5V)÷100μA=45kΩ. Connecting EN to a voltage source directly without a pull-up resistor requires limiting the amplitude of the voltage source to ≤6V to prevent damage to the Zener diode. Under-Voltage Lockout (UVLO) VIN under-voltage lockout (UVLO) protects the chip from operating at an insufficient supply voltage. The UVLO rising threshold is approximately 4.6V, while its falling threshold is 3.9V. Internal Soft Start (SS) A reference-type soft start (SS) prevents the converter output voltage from overshooting during start-up. When the chip starts up, the internal circuitry generates a soft-start voltage (VSS) that ramps up from 0V during the SS time. When VSS is lower than VREF, VSS overrides VREF as the error amplifier reference. www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters The pause command causes the entire chip to enter sleep mode, reducing the quiescent current to improve light- DIO61845 voltage overshoot. Thermal Shutdown Thermal shutdown prevents thermal runaway. When the silicon die temperature exceeds its upper threshold, the entire chip shuts down. When the temperature drops below its lower threshold, the chip is enabled again. Floating Driver and Bootstrap Charging The floating power MOSFET driver is powered by an external bootstrap capacitor. This floating driver has its own UVLO protection with a rising threshold of about 2.4V and a falling threshold of about 300mV. During UVLO, VSS resets to zero. When the UVLO ends, the controller enters soft start. The bootstrap capacitor is charged and regulated to about 5V by the dedicated internal bootstrap regulator. And it will stop charging the bootstrap capacitor when DIO61845 enters pulses-skipping mode, so probe the BS node is forbidden to avoid discharging the bootstrap capacitor. Current Comparator and Current Limit A current-sense MOSFET senses the power MOSFET current. This current is input to the high-speed current comparator for current-mode control. When the power MOSFET turns on, the comparator is first blanked to limit noise, and then compares the power switch current against VCOMP. When the sensed value exceeds VCOMP, the comparator output goes low to turn off the power MOSFET. The maximum current of the internal power MOSFET is limited cycle-by-cycle internally. The switching frequency folds back to prevent an inductor current runaway during start-up or a short circuit. Low Dropout Operation The DIO61845 is designed to operate at almost 100% duty cycle to improve dropout. When the current in the HSFET does not reach the COMP-set current value within one PWM cycle, the HS-FET remains on to prevent a turn-off operation. The HS-FET can remain on for a maximum of 15µs and then turns off for a minimum of 160ns. To prevent the voltage across BST to SW from dropping too low during the low dropout operation, the current comparator enters power-save mode, in which the speed is degraded. This reduces the bootstrap capacitor current consumption when HS-FET turns on for longer than 2µs. Therefore, the voltage across the bootstrap capacitor can remain at a high level (close to 5V). Start-Up and Shutdown If both VIN and VEN exceed their respective thresholds, the chip starts up. The reference block first starts to generate a stable reference voltage and current, and then the internal regulator starts to provide a stable supply for the rest of the circuit. While the internal supply rail is up, an internal timer turns the power MOSFET off for about 50µs to blank any start-up noise. When the internal soft-start block is enabled, it first holds its SS output low to ensure that the rest of the circuit is ready before ramping up. www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters The maximum VSS value is approximately the same as VFB, so if VFB falls, the maximum of VSS falls. This accommodates short-circuit recovery. When the short circuit is removed, VSS ramps up to prevent an output DIO61845 low. The floating driver is not subject to this shutdown command, but its charging path is disabled. Application Information Setting the Output Voltage Set the output voltage of DIO61845 by using a resistor divider (see Figure 2): DIO618 45 R1 FB V OUT R2 Figure 2 FB Resistor Divider to Set VOUT Calculate the output voltage with Equation (1): VOUT = VFB * ( R1 + R 2) R2 (1) The feedback resistor (R1) also sets the feedback loop bandwidth with the internal compensation network. To achieve optimal stability performance and transient response, choose R1 to be around 1.5MΩ in power meter applications with a 12V output rail. Set R1 to be 56kΩ for 5V output rail applications. Then, calculate R2 with Equation (2): R2 = R1 VOUT −1 0 .8V (2) Table 1 lists the recommended feedback resistor values for common output voltages. Table 1 Resistor Selection vs. Output Voltage Setting VOUT R1 R2 5V 56kΩ (1%) 10.7kΩ (1%) 12V 1.5MΩ (1%) 107kΩ (1%) Selecting the Inductor The inductor supplies constant current to the output load while being driven by the switched input voltage. A larger-value inductor results in less ripple current and a lower output ripple voltage but also has a larger physical size, higher series resistance, and lower saturation current. www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters Three events can shut down the chip: EN low, VIN low, and thermal shutdown. During the shutdown procedure, the signaling path is blocked first to avoid any fault triggering. VCOMP and the internal supply rail are then pulled DIO61845 inductance value can be calculated with Equation (3): L1 = VOUT V * (1 − OUT ) f S *△I L VIN (3) Where VOUT is the output voltage, VIN is the input voltage, fS is the switching frequency, and ∆IL is the peak-topeak inductor ripple current. Choose an inductor that will not saturate under the maximum inductor peak current. The peak inductor current can be calculated with Equation (4): I LP = I LOAD + VOUT V * (1 − OUT ) 2 * f S * L1 VIN (4) Where ILOAD is the load current. Additionally, the inductor value influences the DIO61845 load ability during start-up. When the output voltage starts up, fS folds back the minimum to several tens of kHz. Based on Equation (4), a smaller L1 or a lower fS leads to a higher ILP. Therefore, if a small inductor value is used (e.g.: 10μH inductor in a 5V output rail power meter application), the current limit is reached when the DIO61845 starts up with a >250mA constant current load. Then, the output voltage fails to be set up. In this case, for a >250mA constant current load with a 10µH inductor, the DIO61845 must first start up with a load250mA load sufficiently. Selecting the Input Capacitor The input capacitor (C1) can be electrolytic, tantalum, or ceramic. When using electrolytic or tantalum capacitors, add a small, high-quality, ceramic capacitor (C2) (e.g.: 0.1μF) as close to the IC as possible. When using ceramic capacitors, ensure that they have enough capacitance to provide a sufficient charge to prevent excessive voltage ripple at the input. The input voltage ripple caused by the capacitance can be estimated with Equation (5): △VIN = I LOAD VOUT V * * (1 − OUT ) f S * C1 VIN VIN (5) Selecting the Output Capacitor An output capacitor (C4) is required to maintain the DC output voltage. Ceramic, tantalum, or low ESR electrolytic capacitors are recommended. Low ESR capacitors are recommended to keep the output voltage ripple low. The output voltage ripple can be estimated with Equation (6): △VOUT = VOUT V 1 * (1 − OUT ) * ( RESR + ) fS * L VIN 8 * fS * C 4 (6) Where L is the inductor 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 caused mainly by the capacitance. For simplification, the output voltage ripple can be estimated with Equation (7): www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters To determine the inductance, allow the peak-to- peak ripple current in the inductor to be approximately 30% of the maximum load current and choose a peak inductor current below the maximum switch current limit. The DIO61845 VOUT 2 8 * fS * L * C 4 * (1 − VOUT ) VIN (7) 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 with Equation (8): △VOUT = VOUT V * (1 − OUT ) * RESR fS * L VIN (8) The characteristics of the output capacitor also affect the stability of the regulation system. In power meter applications, the output capacitors are large-value electrolytic capacitors, typically, with an RESR and capacitance with a large temperature variation. This large temperature variation changes the part’s feedback loop, making it difficult to keep the loop stable over the full operation temperature, especially when the DIO61845 works in a deep dropout mode (VIN-VOUT25V, due to a low response speed of the current limit loop, there is a risk that the inductor current will rush high when SCP enters with a special slew rate. PCB Layout Guidelines Efficient PCB layout requires high-frequency noise considerations to limit voltage spikes on the SW node. 1. Keep the path of the input decoupling capacitor, VIN, SW, and PGND as short as possible using short and wide traces. 2. Keep the passive components as close to the device as possible. 3. Run the feedback trace far from the inductor and noisy power traces. If possible, run the feedback trace on the opposite side of the PCB from the inductor, separated by a ground plane. Expect greater switching losses at high switching frequencies. 4. Add a grid of thermal vias under the exposed pad to improve thermal conductivity. 5. Use small vias (15mil barrel diameter) so that the hole fills during the plating process and prevent solder wicking during the reflow process associated with larger vias. 6. Use a pitch (distance between the centers) of approximately 40mil between the thermal vias. www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters Table 2 Components Selection Guide DIO61845 Figure 3. Quiescent Current vs. Junction Temperature Figure 4. Vin UVLO vs. Junction Temperature Figure 5. EN Threshold vs. Junction Temperature Figure 6. Efficiency vs. Load Current Iout=0.125A Iout=0.4A Figure 7. Output Voltage Ripple Figure 8. Output Voltage Ripple www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters Typical Performance Characteristic DIO61845 Iout =0.6A Figure 9. Steady State Figure 10. Steady State Iout=0A Iout=0.6A Figure 11. Start up through Vin Figure 12. Start up through Vin Iout=0A Iout=0.6A Figure 13. Shutdown through Vin Figure 14. Shutdown through Vin www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters Iout =0A DIO61845 Iout=0.6A Figure 15. Start up through EN Figure 16. Start up through EN Iout=0A Iout=0A Figure 17. Shutdown through EN Figure 18. Shutdown through EN Iout=0A to short circuit Iout=0.6A to short circuit Figure 19. SCP Entry Figure 20. SCP Entry www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters Iout=0A DIO61845 Figure 21. SCP Steady State Figure 22. SCP Recovery short circuit to Iout=0.6A Iout=0.3A0.6A 1.6A/us Figure 23. SCP Recovery Figure 24. Load Transient Iout=10mA0.6A 1.6A/us Figure 25. Load Transient www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters short circuit to Iout=0A DIO61845 Dioo is a professional design and sales corporation for high-quality and performance analog semiconductors. The company focuses on industry markets, such as, cell phone, handheld products, laptop, and medical equipment and so on. Dioo’s product families include analog signal processing and amplifying, LED drivers and charger IC. Go to http://www.dioo.com for a complete list of Dioo product families. For additional product information, or full datasheet, please contact with our Sales Department or Representatives. www.dioo.com © 2021 DIOO MICROCIRCUITS CO., LTD DIO61845• Rev. 1.2 40V, 0.6A, 2MHz, Synchronous, Step-Down Converter for Power Meters CONTACT US