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PS0100-3.0 Datasheet(PDF) 10 Page - Power IC Ltd. |
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PS0100-3.0 Datasheet(HTML) 10 Page - Power IC Ltd. |
10 / 13 page PS0100 OPERATION The PS0100 is a compact, high-efficiency, synchronous boost converter in a SOT-26 package designed for space- restricted applications. The part is available with adjustable output voltages ranging from 2.5V to 5.0V. It is able to start up with input voltages as low as 0.8V and operate with input voltages down to 0.5V. With its internal synchronous rectifier and low on-resistance of the internal NMOS switch, the device maintains high efficiency over a wide range of load current. As shown in the Block Diagram, the PS0100 consists of accurate band gap core, error amplifier, start-up oscillator and control logic unit along with PMOS and NMOS switches. With current mode PWM control, the PS0100 has ultra-fast line and improved load regulation. Moreover, the PS0100 provides real shutdown circuitry which disconnects the output from the input during shutdown and results in the discharge of the output to ground. conductive path through the body of the PMOS, the output is allowed to go to zero during shutdown, drawing zero current from the input. Output Voltage Selection The PS0100 features a user-adjustable output through an external feedback network. A voltage divider from VOUT to ground programs the output voltage via FB from 2.5V to 5V using the following equation: = V July 2007 www.picsemi.com © 2007 Power IC. All Rights Reserved. 10 Start-Up Mode The PS0100 starts up typically at 0.8V. When it is turned on, the device gets its start up bias from VIN. A start-up oscillator, which runs typically at 650 KHz, takes the output voltage high enough so that VOUT exceeds VIN. Once VOUT exceeds VIN, the internal bias switches from VIN to VOUT by an internal bias-select circuit. Thus, once started (i.e. VOUT exceeds VIN), the internal circuit bias is completely independent of VIN. The start-up oscillator runs at 66% duty cycle at around 650KHz. Once VOUT exceeds VIN (typically 1.9V), the start-up oscillator is disabled and the normal fixed TON PWM operation takes over. Internal PMOS and NMOS Switches The PS0100 features a 0.45 Ω NMOS switch and a 0.6Ω PMOS switch. In normal operation, these switches are alternatively turned on and thus initiate the charging of the inductor from VIN and then discharging of it to the output capacitor and the load. However, between the event of one switch turning off and the other turning on, a dead time is provided to avoid a huge in-rush current from the output to ground via switches. During the dead time, both switches remain off and the inductor discharges via the body diode of the PMOS switch to the output. True Shutdown Mode The PS0100 is designed to allow for true shutdown by managing the body diode of the PMOS switch. As the PMOS switch is turned off and there is no VOUT REF × [1 + (R1/R2)] where, VREF = 1.0V Thermal Overload Protection Thermal overload protection limits the total power dissipation in the PS0100. When the junction temperature exceeds TJ = +145°C, the thermal sensor signals the shutdown logic and turns off most of the internal circuitry. The thermal sensor turns the internal circuitry on again after the IC’s junction temperature drops by 15 °C. Thermal overload protection is designed to protect the PS0100 in the event of a fault condition. For continuous operation, do not exceed the absolute maximum junction temperature rating of TJ = +125°C. Current Limit and Short Circuit Protection The PS0100 includes a current limiter that monitors the peak inductor current through the NMOS switch and turns the NMOS switch off when the inductor peak current exceeds 850mA. Because of its true shutdown feature, the IC is allowed to be short-circuited. The thermal shutdown turns off the regulator in the event of excessive heating when the die temperature reaches 145 °C. Light Load Operation The PS0100 provides improved light load efficiency. The internal zero current comparator monitors the inductor current to the load and shuts off the PMOS switch once this current reduces to some low value (typically 50mA). This prevents the inductor current from reversing its polarity, avoiding back-charging and thus improving the efficiency at light loads. At that time, both the NMOS and PMOS switches remain off. However, normal operation starts again when the output voltage falls below the regulation point. The IC automatically skips pulses at light load, thus providing better efficiency. |
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Similar Description - PS0100-3.0 |
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