New TI TPS7A4700

Just got in the mail information on the new TI ultra low noise regulator, the TI TPS7A4700

• Can source 1 A of current
• Noise figure of 4.5 uV, puts it at the top of the regulator list
• Voltage configurable evaluation board can be purchased for $20.

Is there a reason to use anything else?

The TPS7A47 is designed with bipolar technology primarily for high-accuracy, high-precision instrumentation implications where clean voltage rails are critical to maximize system performance. This feature makes the device ideal for powering operational amplifiers, analog-to-digital converters (ADCs), digital-to-analog converters (DACs), and other high performance applications…

Seems they designed this part for us diy audio nuts! 🙂

I’ve been thinking about what to use to power Ian’s FIFO reclocker board. This is its perfect match.

Load Step Transient Response

The load step transient response is the output voltage response by the LDO to a step change in load current whereby output voltage regulation is maintained. The worst-case response is characterized for a load step of 10 mA to 1 A (at 1 A per microsecond) and shows a classic critically-damped response of a very stable system. The voltage response shows a small dip in the output voltage when charge is initially depleted from the output capacitor and then the output recovers as the control loop adjusts itself. The depth of the charge depletion immediately after the load step is directly proportional to the amount of output capacitance. However, to some extent, the speed of recovery is inversely proportional to that same output capacitance. In other words, larger output capacitance act to decrease any voltage dip or peak occurring during a load step but also decrease the control-loop bandwidth, thereby slowing response.

The worst-case off-loading step characterization occurs when the current step transitions from 1 A to 0 mA. Initially, the LDO loop cannot respond fast enough to prevent a small increase in output voltage charge on the output capacitor. Because the LDO cannot sink charge current, the control loop must turn off the main pass-FET to wait for the charge to deplete, thus giving the off-load step its typical monotonic decay (which appears triangular in shape)