Triple channel current mode PWM step-down DC/DC converter released
29 April 2008
Linear Technology has announced the launch of the LT3507; a 2.5MHz, 36V triple step-down DC/DC converter with LDO controller
One channel is capable of delivering up to 2.4A of output current while the other two switching regulators can deliver 1.5A of continuous output current. Additionally, an integrated LDO controller combined with an external transistor can be connected to VOUT of any of the switching regulators or can be run directly from the input voltage, offering a fourth low noise channel.
Its input range of 4V to 36V makes it ideal for regulating power from a wide variety of sources from fixed input rails, 24V industrial supplies and automotive batteries. As each switching regulator has its own input pin, up to three different voltage rails can drive the LT3507, offering maximum efficiency for each channel.
For automotive applications, the LT3507’s minimum input voltage of 4V enables it to meet the low input voltage requirements for automotive cold start conditions. Similarly, its 36V input capability enables it to withstand transients commonly found in load-dump scenarios. The LT3507’s 250kHz to 2.5MHz switching frequency is user programmable, enabling it to maximise efficiency while avoiding critical frequency bands such as AM radio bands in automotive applications. Its high frequency operation also enables the use of low cost inductors and ceramic capacitors, resulting in low, predictable output ripple.
The LT3507’s low VCESAT (400mV at 2A and 350mV at 1.5A) internal switches offer efficiencies of up to 88 per cent eliminating the need for external heat sinking. All three of the LT3507’s converters are synchronised to either a common external clock input or its internal oscillator. The 2.4A channel maintains a 180-degree phase offset between the two 1.5A channels to reduce input ripple current.
An internal 0.80V reference enables sub 1V output voltages required to power the latest generation of low voltage DSPs and microcontrollers. Independent Run, Tracking/Soft-start and PowerGood indicators ease supply sequencing. Other features include cascadability and user programmable overvoltage and undervoltage lockouts. The low current (<1µA) shutdown provides extended run-time in battery-powered systems.
The LT3507EUHF is available now in a 5mm x 7mm QFN-38 package.
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