Data Sheet

LT3077

analog.com

Rev. 0

30 of 38

BIAS/BIASF Pin Requirements

The BIAS pin supplies current to most of the internal control circuitry and the output stage, which drives the pass

transistor. The LT3077 requires a minimum 2.2μF bypass capacitor on the BIASF pin for stability and proper

operation. No bypass capacitor is needed on the BIAS pin. To ensure proper operation, the BIAS voltage must satisfy

the following conditions: 2.375V ≤ VBIAS ≤ 5.5V and VBIAS ≥ (VOUT + 1.2V). For VOUT ≤ 1.15V, the minimum BIAS voltage is

limited to 2.375V.

Load Regulation

The LT3077 corrects for a parasitic package, and PCB I-R drops when the SENSE pin is Kelvin connected to output

capacitors. The LT3077 handles moderate levels of output line impedance, but excessive impedance between VOUT

and COUT causes an excessive phase shift in the feedback loop and adversely affects stability.

PCB Layout Considerations

Given the LT3077’s high bandwidth and high PSRR, careful PCB layout must be employed to achieve full device

performance. Figure 69 shows the EVAL-LT3077-AZ evaluation board with a layout that delivers the full performance

of the regulator. Refer to the EVAL-LT3077-AZ evaluation board user guide for further details.

Figure 69. EVAL-LT3077-AZ Evaluation Board

Protection Features

The LT3077 has an internal current limit that clamps output current to 4.5A. In addition, the LT3077 has a ±10%

accurate programmable precision current limit. The die junction temperature can exceed the 125°C maximum

operating temperature if the ambient temperature is high enough. If this occurs, the LT3077 relies on an internal

thermal safety feature. Typically at 168°C, the LT3077 thermal shutdown engages and the output is shut down until

the IC temperature falls below its thermal hysteresis limit.

Externally Programmable Current Limit

The ILIM pin’s current limit threshold is 1V. Connecting a resistor from ILIM to GND sets the maximum current flowing

out of the ILIM pin, which in turn, programs LT3077’s current limit. With a 3A x kΩ programming scale factor, the

current limit can be calculated as follows:

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