Need more spec for ~SHDN on U1V11F5 Step-up 5V Reg

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1

Because, I need a step-up reg [SUR] that will supply 5V from an UltraCap and I want the SUR to draw as little current as possible when the device is not running. So, in other words, the device will, most of the time, sit in standby – it will spend a lot of time on a wireless charging pad, but for those times when it is lying on a table (for instance), I don’t want it to be draining the UltraCap down. SO, I’m thinking of a resistor tying the ~SHDN to Gnd with a push button that will apply the UltraCap voltage (2.5V max) to the ~SHDN pin to wake the SUR up, which will raise VDD on a µController and associated parts and essentially turn the device on. And, I need this to work for the full range of Vin on the SUR [e.g. 0.5V to 2.5V for a U1V11F5, for example].

Sooooo… if the U1V11F5 can do all of that, then it qualifies as the SUR – can anyone verify that?

I also need to know the input drive/leakage current for the ~SHDN input [so I can determine the value of the pull-down resistor].

2

Hello.

The shutdown pin is pulled up to VIN through a 100 kΩ resistor. Using a resistor to pull down the shutdown pin will effectively create a voltage divider. Since the pin requires a voltage lower than 0.4V (or even lower depending on the input voltage) to power down the regulator, I do not think there is much benefit in using a resistor to pull down the pin (it is probably not as reliable as pulling it directly to ground). You can find more information in the “Connections” section on the U1V11F5 switching step-up voltage regulator product page.

- Jeremy