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Data Sheet

LT3046

analog.com

Rev 0

24 of 47

APPLICATIONS INFORMATION

The LT3046 is a high-performance, low-dropout, linear regulator featuring Analog Devices’ ultra-low noise

(2.2nV/√Hz at 10kHz) and ultra-high PSRR (82dB at 1MHz) architecture for powering noise-sensitive applications.

Designed as a precision current source followed by a high-performance rail-to-rail voltage buffer, the LT3046 can

be easily paralleled to further reduce noise, increase output current, and spread heat on the PCB. The device

additionally features programmable current limit, fast start-up capability, and programmable power good.

The LT3046 is easy to use and incorporates all of the protection features expected in high-performance regulators.

Included are short-circuit protection, safe operating area protection, reverse-battery protection, reverse-current

protection, and thermal shutdown with hysteresis.

Output Voltage

The LT3046 incorporates a precision 100μA current source flowing out of the SET pin, which also connects to the

inverting input of the error amplifier. Figure 67 illustrates that connecting a resistor from SET to ground generates a

reference voltage for the error amplifier. This reference voltage is the product of the SET pin current and the SET

pin resistor. The unity-gain configuration of the error amplifier produces a low-impedance version of this voltage

on its noninverting input, that is, the OUTS pin, which is externally connected to the OUT pin.

Figure 67. Basic Adjustable Regulator

The rail-to-rail error amplifier and current reference of the LT3046 allows for a wide output-voltage range from 0.2V

to VIN minus dropout, up to 19V. A PNP-based input pair is active for a 0.2V to ~0.95V output and an NPN-based

input pair is active for output voltages greater than ~0.95V, with an abrupt transition between the two input pairs at

~0.95V output with approximately 28mV of hysteresis. While the NPN-based input pair is designed to offer the best

overall performance, see Table 1 for details on the offset voltage, SET pin current, output noise, and PSRR variation

with the error-amplifier input pair. Table 5 lists many common output voltages and their corresponding 1% RSET

resistors.

Table 5. 1% Resistor for Common Output Voltages

VOUT (V)

RSET (kΩ)

2.5

24.9

3.3

33.2

49.9

121

150

180

4.7µF

0.47µF

33.2kΩ

100µA

EN/UV

PGFB

VIN

5V ±5%

SET

GND

ILIM

OUTS

OUT

LT3046

VOUT

3.3V

IOUT(MAX)

200mA

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