MCP4241 Shutdown Pin

Quick question. I'm working with MCP4241 digital pot IC and it has shutdown pin which disconnects one of the terminals from wiper. But I have no idea how to activate it. Normally I have it connected to VCC (HIGH) but I tried connecting it to Ground (LOW) and it didn't seem to do anything. It's not immediately clear to me from datasheet how to activate it (or I didn't find it).

When the SHDN pin is forced active (VIL):
• The P0A and P1A terminals are disconnected
• The P0W and P1W terminals are simultaneously
connect to the P0B and P1B terminals

You have to read through a lot of crap to reach it, but the explanation is there. Section 5.4, Figure 5.2 makes it pretty clear what the state of the device is, when the shutdown bit is 0.

Unfortunately I don't understand much of it.
Can someone who has more experience than me please help me? :slight_smile:
I just want to Shutdown chip. What do I need to do to accomplish this?
Set SHDN pin (12) to HIGH or LOW or leave floating?
What kind of command bit I need to send via SPI?
I'm using this function to control chip:

void writeMCP4241(byte address, byte value) {
  digitalWrite(SlaveSelect, LOW); 
  SPI.transfer(address << 4);
  SPI.transfer(value & 127);
  digitalWrite(SlaveSelect, HIGH);
}

Figure 5.2 of the datasheet shows the configuration of the "pot" when the Shutdown pin is low.
What are you having difficulty to understand?

bratan:
Quick question. I'm working with MCP4241 digital pot IC and it has shutdown pin which disconnects one of the terminals from wiper. But I have no idea how to activate it. Normally I have it connected to VCC (HIGH) but I tried connecting it to Ground (LOW) and it didn't seem to do anything. It's not immediately clear to me from datasheet how to activate it (or I didn't find it).

When the SHDN pin is forced active (VIL):

VIL means voltage input low. So its active low.

All (voltage controlled) logic families have VIL/VIH/VOL/VOH specs, an input has
to be below VIL to read low, above VIH to read high.

[also I just checked the datasheet, the signal is clearly active low as it has a line
over the top, which means active-low or negative-logic - this is a standard boolean
algebra convention]

MarkT:
VIL means voltage input low. So its active low.

All (voltage controlled) logic families have VIL/VIH/VOL/VOH specs, an input has
to be below VIL to read low, above VIH to read high.

[also I just checked the datasheet, the signal is clearly active low as it has a line
over the top, which means active-low or negative-logic - this is a standard boolean
algebra convention]

Thank you Mark! I wasn't sure what active-low condition is.
Anyway I figured it out.
Put pulldown resistor between shutdown pin and GND. Then change pin to LOW to shut down, or to high to turn it back on.