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1A, 0.5V ultra-LDO voltage regulator with programmable soft-start or programmable over current protection

16th March 2012

Torex Semiconductor

ES Admin

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The new XC6603/04 series from Torex is a high speed and highly accurate LDO family which can supply up to 1A of output current while consuming only 100µA. With the help of a bias voltage that can be set between 2.5V and 6.0V, the XC6603/04 operates with input voltages from 0.5V to 3.0V and is readily available with fixed output voltages from 0.5V to 1.8V in 0.1V increments.

It is thanks to its integrated N-ch driver transistor that the minimum input and output voltages of the XC6603/04 can be much lower than more traditional LDO’s with their integrated P-ch transistors. Another advantage of the XC6603/04 integrated N-ch driver transistor is that it dramatically reduces the on-resistance at low output voltages, leading to dropout voltages as low as 155mV @ 1A with VOUT=1.2V (VBIAS=3.6V). This makes the XC6603/04 ideally suited for low input/output voltage applications which require high output current and extended battery life.

With the XC6603/04, ceramic capacitors values as low as 1µF (VIN, VBIAS) and 2.2µF (VOUT) can be used, even with an output current of 1A. This can provide a very compact solution. Although the use of such small capacitor values contributes to lower the inrush current at start-up, the built-in soft-start circuit makes sure that this inrush current is always kept under control, even under very high output current variations at start-up.

Additionally the XC6603 allows the user the option to program the soft start time externally with a capacitor connected between the SS Pin and ground. The XC6604 also includes an optional softstart circuit, but the time is set internally at 600μs (max).

Besides its inrush current protection, the XC6603/04 comprises a combination of a current limiter circuit and a foldback short-circuit protection, as well as a thermal shutdown circuit that turns the N-ch driver transistor off when the junction temperature of the IC reaches 150°C.

Furthermore with the XC6604 the current limit threshold can be programmed externally, between 0.5A～1.3A by connecting a resistor to the ILIM Pin.

Other functionalities of the XC6603/04 include an enable pin which turns the IC on and off, a CL discharge function which quickly brings the output voltage down to VSS level when entering standby mode, and an under voltage lock out (UVLO) circuit which makes sure that the voltage at the VBIAS and VIN pins are high enough to guarantee proper regulation of the output voltage.

The XC6603/04 is available in a tiny USP-6C package for applications that require both a small form factor and a good amount of power dissipation as well as in a standard SOT-26W package.