Ultra Low Dropout Voltage Regulator from Torex Semiconductor

17th July 2008

ES Admin

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New from Torex Semiconductor is the XC6601, a 400mA high-speed voltage regulator with a built-in N-channel FET. With a dropout voltage of only 35mV at 100mA, the XC6601 is ideal for low dropout applications.

The XC6601 consists of a voltage reference, error amplifier, driver transistor, current limiter, fold-back circuit, thermal shutdown circuit, under voltage lockout (UVLO) and a phase compensation circuit. The device is available in a wide range of ultra small USP-6C, SOT-25 and SOT89-5 packages, making it ideal for portable applications.

The new XC6601 voltage regulator consumes only 1.0µA in normal operation, falling to less than 0.01µA in standby mode. Output voltage can be factory set anywhere from 0.7V to 1.8V in 50mV steps, and the operating voltage range is from 1.0V to 3.0V. The LDO is also compatible with low ESR ceramic capacitors, which give added output stability. Thanks to the ultra low ON resistance of the FET – almost half that of a conventional LDO such as Torex's XC6210 at VBIAS = 3.6V – high efficiency operation is possible, even at low output voltages.

The internal N-channel driver is powered from the VBIAS pin, which is connected directly to the main power source, for example, a lithium ion battery. By connecting the VIN pin of the XC6601 to the output of a step-down DC-DC converter such as Torex’s 3MHz switching XC9236, for example, the device can be used to provide low, stable output voltages (down to 0.7V) from equally low inputs!

The XC6601 has built-in over current protection and thermal shutdown circuits. These two protection circuits will operate when the output current reaches its current limit or the junction temperature reaches its temperature limit. With the built-in UVLO function, the regulator output is forced OFF when the VBIAS pin or the VIN pin drops below the UVLO voltage level.

The CE (chip enable) function enables design engineers to turn off the output, putting the device into standby mode, thereby greatly reducing power consumption. In addition, during the switch into standby mode, the electric charge at the CL capacitor is discharged via the internal auto-discharge switch, ensuring that the VOUT pin drops down to ground quickly.