Electronics News
Archive : 22 May 2008 год
08:05Digitally programmable front-end power supplies
Emerson Network Power, has launched a series of programmable ac-dc front-end power supplies that provide a power density of 1.3 watts per cubic centimetre. The UFE series power supplies have a 140mm x 273mm footprint and a height of 41mm, enabling up to three supplies to be contained on a single 1U high 19 inch (483 mm) rack-mounting chassis. The highest power model in the series – the UFE2000 – has a 2 kW output rating, so OEMs and system integrators can now configure individual power shelves with up to 6 kW of available power, or up to 4 kW of redundant power. Furthermore, the power supplies can be stacked up to 6U high, to provide up to 36 kW of available power. The UFE series currently comprises two models – a 24 Vdc output model with a power rating of 1,300 watts, and 48Vdc output model with a power rating of 2,000 watts.
Both power supplies generate a main payload output and an auxiliary 260 mA @ 11 Vdc output for powering standby circuitry. The 1,300 watt model has a range 90 to 264 Vac input and can deliver up to 65 A from its main output, while the 2,000 watt model has a 180 to 264 Vac input, and can deliver up to 52 A from its main output. The main output of each power supply is isolated and floating, enabling positive or negative polarity operation, and has a hold-up time of 20 ms minimum at full rated power. The power supplies’ main output is digitally programmable, and users have a choice of standard I2C or advanced PMBus communications. The output of 48 Vdc model can be adjusted over the range 42 to 57 Vdc, while the output of the 24 Vdc model can be adjusted over the range 21 to 28.5 Vdc. In both cases, the output voltage can be adjusted on the fly, with a setpoint accuracy of ±0.5 percent.
UFE series power supplies employ an advanced power conversion topology and use a fixed 450 kHz switching frequency to minimize RFI and maximize efficiency – they provide a full load efficiency of up to 91 percent. The supplies have no minimum load requirement, and support current sharing via internal ORing FETs (Field Effect Transistors). In standard operational mode, the supplies’ tight dynamic regulation ensures that the main output voltage will not deviate by more than 2.5 percent for a 25 percent step change in load current. However, the supplies also offer a droop compensation mode to help balance current sharing; when enabled, this increases the dc output impedance of the power supply, thereby lowering its output voltage, as the load current increases. The 48 Vdc models have a droop characteristic of 80.6 mV/A from 10 A up to the supplies’ power limit, and the 24 Vdc model has a 40.3 mV/A characteristic.
The power supplies are primarily intended for high availability central office, telecommunications and server type applications, such as data centres. A three-slot rack, known as a UFR6000, is available. The power supplies are hot pluggable and are comprehensively protected against faults – including overvoltage, overcurrent, overpower, overtemperature and short-circuit conditions. They also feature extensive remote monitoring and diagnostic facilities – the supply’s output current and voltage, internal temperature and hours of operation values can be retrieved via I2C or PMBus – and realtime alarms are provided in the event of an ORing fault or fan failure.
UFE series power supplies incorporate low-noise fan cooling with automatic speed control, and have an ambient operating temperature range of -33 to +70 degrees Celsius. They can cold- start from temperatures as low as -40 degrees Celsius. The power supplies meet the rigorous EN55022-B and FCC part 15 Class B conducted emissions standards, and comply with applicable EMC immunity standards, including EN61000-3-2 and EN61000-4-2, -3, -4, -5, -6 and -8. The supplies carry VDE EN/IEC60950-1 and UL/cUL/VDE 60950-1 safety approvals. Sample quantities of UFE series power supplies are available for immediate delivery. Standard lead-time is stock to 8 weeks.
Pricing starts at US $665 for both models, in quantities of 100.
Both power supplies generate a main payload output and an auxiliary 260 mA @ 11 Vdc output for powering standby circuitry. The 1,300 watt model has a range 90 to 264 Vac input and can deliver up to 65 A from its main output, while the 2,000 watt model has a 180 to 264 Vac input, and can deliver up to 52 A from its main output. The main output of each power supply is isolated and floating, enabling positive or negative polarity operation, and has a hold-up time of 20 ms minimum at full rated power. The power supplies’ main output is digitally programmable, and users have a choice of standard I2C or advanced PMBus communications. The output of 48 Vdc model can be adjusted over the range 42 to 57 Vdc, while the output of the 24 Vdc model can be adjusted over the range 21 to 28.5 Vdc. In both cases, the output voltage can be adjusted on the fly, with a setpoint accuracy of ±0.5 percent.
UFE series power supplies employ an advanced power conversion topology and use a fixed 450 kHz switching frequency to minimize RFI and maximize efficiency – they provide a full load efficiency of up to 91 percent. The supplies have no minimum load requirement, and support current sharing via internal ORing FETs (Field Effect Transistors). In standard operational mode, the supplies’ tight dynamic regulation ensures that the main output voltage will not deviate by more than 2.5 percent for a 25 percent step change in load current. However, the supplies also offer a droop compensation mode to help balance current sharing; when enabled, this increases the dc output impedance of the power supply, thereby lowering its output voltage, as the load current increases. The 48 Vdc models have a droop characteristic of 80.6 mV/A from 10 A up to the supplies’ power limit, and the 24 Vdc model has a 40.3 mV/A characteristic.
The power supplies are primarily intended for high availability central office, telecommunications and server type applications, such as data centres. A three-slot rack, known as a UFR6000, is available. The power supplies are hot pluggable and are comprehensively protected against faults – including overvoltage, overcurrent, overpower, overtemperature and short-circuit conditions. They also feature extensive remote monitoring and diagnostic facilities – the supply’s output current and voltage, internal temperature and hours of operation values can be retrieved via I2C or PMBus – and realtime alarms are provided in the event of an ORing fault or fan failure.
UFE series power supplies incorporate low-noise fan cooling with automatic speed control, and have an ambient operating temperature range of -33 to +70 degrees Celsius. They can cold- start from temperatures as low as -40 degrees Celsius. The power supplies meet the rigorous EN55022-B and FCC part 15 Class B conducted emissions standards, and comply with applicable EMC immunity standards, including EN61000-3-2 and EN61000-4-2, -3, -4, -5, -6 and -8. The supplies carry VDE EN/IEC60950-1 and UL/cUL/VDE 60950-1 safety approvals. Sample quantities of UFE series power supplies are available for immediate delivery. Standard lead-time is stock to 8 weeks.
Pricing starts at US $665 for both models, in quantities of 100.
Source: www.channel-e.biz
08:04USB Battery Charger
Linear Technology announces the LTC3558, a multi-function power management solution for handheld applications. The LTC3558 integrates a stand-alone Li-Ion/Polymer battery charger and two synchronous regulators - one buck-boost and one buck - and is offered in a 3mm x 3mm QFN package. The linear battery charger can deliver up to 950mA charge current from a wall adapter supply, or up to 500mA charge current from a USB port. The LTC3558’s stand-alone autonomous operation simplifies design, eliminating the need for an external microprocessor for charge termination. Both switching regulators are designed to operate over the Li-Ion/Polymer range of 2.7V to 4.2V while delivering output currents up to 400mA each.
The LTC3558’s integrated synchronous buck regulator features 100% duty cycle operation, while the buck-boost regulator is capable of regulating its programmed output voltage (typically 3.3V) over the entire Li-Ion/Polymer operating range. The integrated RDS(ON) switches enable efficiencies as high as 92%, maximizing battery run time. In addition, Burst Mode operation optimizes efficiency at light loads with a quiescent current of 20uA for the buck-boost and 35uA for the buck (<1uA in shutdown for each). The 2.25MHz switching frequency allows the utilization of tiny low cost capacitors and inductors less than 1mm in height. Furthermore, the regulators are stable with ceramic output capacitors.
The LTC3558’s battery charger contains USB functionality, including 20%/100% full-scale charge current setting, a SUSP pin for shutdown/enable, and 4 different indication states on the /CHRG pin. The final battery float voltage is accurate to ±0.5%. The charger’s thermal regulation scheme maximizes the charge rate without the risk of overheating, while the NTC input allows temperature-qualified charging. To preserve battery energy, the LTC3558 draws <3uA from the battery in suspend mode. The charger is compatible with inputs up to 5.5V (7V absolute maximum transient for added robustness).
Pricing starts at $2.35 each for 1,000-piece quantities.
The LTC3558’s integrated synchronous buck regulator features 100% duty cycle operation, while the buck-boost regulator is capable of regulating its programmed output voltage (typically 3.3V) over the entire Li-Ion/Polymer operating range. The integrated RDS(ON) switches enable efficiencies as high as 92%, maximizing battery run time. In addition, Burst Mode operation optimizes efficiency at light loads with a quiescent current of 20uA for the buck-boost and 35uA for the buck (<1uA in shutdown for each). The 2.25MHz switching frequency allows the utilization of tiny low cost capacitors and inductors less than 1mm in height. Furthermore, the regulators are stable with ceramic output capacitors.
The LTC3558’s battery charger contains USB functionality, including 20%/100% full-scale charge current setting, a SUSP pin for shutdown/enable, and 4 different indication states on the /CHRG pin. The final battery float voltage is accurate to ±0.5%. The charger’s thermal regulation scheme maximizes the charge rate without the risk of overheating, while the NTC input allows temperature-qualified charging. To preserve battery energy, the LTC3558 draws <3uA from the battery in suspend mode. The charger is compatible with inputs up to 5.5V (7V absolute maximum transient for added robustness).
Pricing starts at $2.35 each for 1,000-piece quantities.