Dual 500mA µPower LDO Features Independent 1.8V–20V Inputs and Easy Sequencing in a 4mm × 3mm DFN

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The LT3029 integrates two independent 500mA monolithic LDOs in a tiny 16-lead MSOP or 4mm × 3mm × 0.75mm DFN package. Both regulators have a wide 1.8V to 20V input voltage range with a 300mV dropout voltage at full load. The output voltage is adjustable down to the 1.215V reference voltage. With an external bypass capacitor, the output voltage noise is less than 20µV_RMS. A complete power supply requires only a minimum 3.3µF ceramic output capacitor for each channel to be stable.

Quiescent current is 55µA per channel, dropping below 1µA in shutdown. Reverse-battery protection, reverse-current protection, current limit foldback and thermal shutdown are all integrated into the package, making it ideal for battery-powered systems.

The LT3029 includes features that simplify the design of multivoltage systems. Its two independent regulators present separate input and shutdown pins. It is also compatible with the LTC2921, LTC2922 and LTC2923 power supply tracking controllers, allowing for easy multirail power supply tracking and sequencing design.

Table 1. Comparison between dual channel LDOs
	V_IN RANGE (V)	I_OUT (mA)	DROPOUT VOLTAGE @ I_OUT (mV)	INDEPENDENT V_IN	I_Q/CHANNEL (µA)	DFN PACKAGE SIZE
LT3023	1.8~20	100/100	300/300	N	20	3mm × 3mm
LT3024	1.8~20	100/500	300/300	N	30	4mm × 3mm
LT3027	1.8~20	100/100	300/320	Y	25	3mm × 3mm
LT3028	1.8~20	100/500	300/300	Y	30	5mm × 3mm
LT3029	1.8~20	500/500	300/300	Y	55	4mm × 3mm

Two Independent Regulators

The LT3029’s inputs can be used independently or combined. Figure 1 shows an application generating two output voltages from two different input voltages, with independent shutdown control for each channel.

Figure 1. Completely independent channels have separate input and SHDN pins.

Different Start-up Slew Rates

Start-up time is roughly proportional to the bypass capacitance, regardless of the input and output voltage. The output capacitance and the load characteristics also have no influence on the result. Figure 2 shows the regulator start-up time versus bypass capacitance.

Figure 2. Start-up time vs bypass capacitor value.

The LT3029 is compatible with LTC292x series of power supply sequencing and tracking controllers. Its ADJ pin should be connected to LTC292x FB pin. By choosing the right resistors, it can track or sequence the power supply. Please refer to the LTC2923 data sheet for details.

Conclusion

The LT3029 is a dual 500mA/500mA monolithic LDO with a wide input voltage range and low noise. The two channels are fully independent, allowing for flexible power management. It is ideal for battery-powered systems because of its low quiescent current, small package and integration of battery protection features.