LT3046 200mA, Ultra-Low Noise Linear Regulator

The LT3046 is an ultra-low noise linear regulator from Analog Devices, designed to provide 200mA of current with high PSRR (Power Supply Rejection Ratio), and high accuracy output voltage. The LT3046 can supply 200mA at a typical 300mV dropout voltage. It has a wide input voltage range from .2V to 19V. This IC is designed as a precision current reference followed by a high-performance voltage buffer that can be paralleled to reduce noise further, increase output current, and spread heat on the PCB. The normal operating quiescent current is nominally 3.7mA and drops to 26μA in shutdown. Additionally, the LT3046 offers a programmable current limit, fast start-up capability, and programmable power good to indicate output voltage regulation. This small voltage also comes with reverse-battery protection, reverse-current protection, internal current limit with fold back and thermal limit with hysteresis. The LT3046 is available in a thermally enhanced, 12-lead, 3mm × 3mm, DFN package. 

LT3046 Pinout Configuration

Here are the pinout details for LT3046.      

Features of LT3046

The LT3046 regulator has the following key features:

• Ultra-Low RMS Noise: 0.8μVRMS (10Hz to 100kHz) 
• Ultra-Low Noise: 2.2nV/√Hz at 10kHz  
• Ultra-Low 1/f Noise: 2.5μVP-P (0.1Hz to 10Hz)
• Ultra-High PSRR: 82dB at 1MHz
• Output Current: 200mA  
• Wide Input-Voltage Range: 2.2V to 20V
• Single Capacitor Improves Noise and PSRR
• SET Pin Current: 100μA, ±0.5% Initial Accuracy
• Single Resistor Programs Output Voltage
• Programmable Current Limit 
• Low Dropout Voltage: 300mV
• Output-Voltage Range: 0.2V to 19V
• Programmable Power Good
• Fast Start-Up Capability
• Precision Enable/UVLO
• Parallelable for Lower Noise and Higher Current
• Internal Current Limit with Foldback
• Minimum Output Capacitor: 4.7μF Ceramic
• Compact, Low-Profile, 12-Lead, 3mm × 3mm, DFN Package 

Manufacturers of LT3046:

ANALOG DEVICES manufactures the LT3046. There are no alternative manufacturers for the same part number as of the date of writing this article. 

ADM7171 Equivalents

There are no pin-to-pin compatible equivalents for LT3046.

LT3046 Alternatives

If you are looking for an alternative for LT3046 you can look at the other IC from these.

LM2596, XL6009, MC34063, MP9486, MP1584, TPS54231, LM2576, CS1411, LT1070, RT8059, NCP3170, LT1370, ADM7171, LT1765

Note: Complete technical details can be found in the LT3046 datasheet at this page’s end.

LT3046 Circuit Diagram

The following image shows a simple circuit diagram for LT3046.

The LT3046 circuit is configured to output a regulated 3.3V with a maximum current of 200mA. 
The 4.7µF capacitor provides input voltage filtering to reduce noise and stabilise the input voltage to the LT3046. The resistor divider network (200kΩ resistor) sets the Undervoltage lockout threshold. When the input voltage is below a certain level, the LT3046 will be disabled to prevent unstable operation.PG pin indicates if the output voltage is within the specified range. It is connected to the resistor divider network to provide feedback. The SET pin is used to set the output voltage. The resistor connected to this pin determines the output voltage of the LT3046. Output Capacitor provides output voltage filtering, reducing noise and ensuring stable output voltage.OUTS pin is connected to the output voltage and provides feedback for regulation. Divider Network (453kΩ and 49.9kΩ) is used to set the output voltage. The ratio of these resistors sets the feedback voltage to the LT3046.ILIM pin is used to set the current limit. The LT3046 can be configured to limit the maximum output current.PGFB pin monitors the output voltage and provides a signal if the voltage is within the specified range.

Troubleshooting Tips for LT3046 Circuit

The output voltage of LT3046 is not at the expected level or fluctuates?

Ensure that the resistors used to set the output voltage are of the correct values and are properly connected. Verify that capacitors are within the recommended specifications (low ESR and correct values). Add or check the bypass and output capacitors. A 4.7µF capacitor is typically recommended for both input and output. Ensure the SET pin is properly connected to the resistor network setting the output voltage.

The LT3046 regulator gets too hot and possibly goes into thermal shutdown.

Ensure adequate heat sinking or thermal vias are used. Use a copper area on the PCB to dissipate heat. Ensure the input voltage is within the recommended range and not excessively high compared to the output voltage, which increases power dissipation. Also, check if the load current is within the specified limits. Use an appropriate resistor on the ILIM pin to set the current limit.

Why there is no output voltage present at output even when the input is correctly applied?

Ensure the EN/UV pin is correctly set, and the voltage is above the threshold to enable the regulator. Verify all connections, especially ground and power connections. Confirm that the input voltage is within the operating range and is applied to the correct pin. Check if the regulator is in a faulty condition such as over-temperature or over-current shutdown.

What would be the reason for excessive noise or ripple in the output voltage?

Use low ESR capacitors for input and output filtering. Consider adding additional filtering stages if necessary. Ensure the input supply is clean and well-regulated.

Why doesn’t the PG pin indicate the correct status of the output voltage?

Verify the resistor divider network connected to the PGFB pin is correctly set to monitor the output voltage. Ensure the PG pin is correctly connected to the monitoring circuit.

Things to Consider When Using LT3046 in Your Design

Minimize board leakage by encircling the SET pin with a guard ring that operates at a potential close to itself, ideally connected to the OUT pins. Guarding both sides of the circuit board is recommended. Bulk leakage reduction depends on the guard-ring width. Leakages of 100nA into or out of the SET pin create a 0.1% error in the reference voltage. Leakages of this magnitude, coupled with other sources of leakage, can cause significant errors in the output voltage, especially over a wide operating temperature range. The below figure illustrates a typical guard-ring layout technique. 

Because the SET pin is a high-impedance node, unwanted signals can couple into the SET pin and cause erratic behaviour, which is most noticeable when operating with a minimum output capacitor at heavy load currents. Bypassing the SET pin with a small capacitance to ground resolves this issue, 10nF is sufficient. For applications requiring higher accuracy or an adjustable output voltage, the SET pin can be actively driven by an external voltage source capable of sinking 100μA. Connecting a precision-voltage reference to the SET pin eliminates any errors present in the output voltage due to the reference current and SET pin resistor tolerances.
The LT3046 requires an output capacitor for stability. Given its high bandwidth, Analog Devices recommends low ESR and ESL ceramic capacitors. A minimum of 4.7μF capacitance with an ESR of less than 20mΩ and an ESL of less than 2nH is required for stability.

Applications of LT3046

• RF Power Supplies: PLLs, VCOs, Mixers, LNAs, PAs 
• Very Low-Noise Instrumentationυ
• High-Speed/High-Precision Data Converters
• Post-Regulator for Switching Supplies

2D Model and Dimensions of LT3046

Here you can find the mechanical drawings of LT3046 along with its dimensions. The dimensions can be used to create custom footprints of the IC and be used for PCB or CAD modelling.