Ultra-deep power down mode control in a memory device

1. A method of controlling an ultra-deep power down (UDPD) mode in a memory device, the method comprising:

a) receiving a write command from a host via an interface;

b) beginning a write operation on the memory device to execute the write command;

c) reading an auto-UDPD (AUDPD) configuration bit from a status register during the write operation;

d) completing the write operation on the memory device;

e) automatically entering the UDPD mode upon completion of the write operation in response to the AUDPD configuration bit being set;

f) driving a low impedance output from the memory device in response to a read status register command being received from the host while the memory device is in the UPDP mode; and

g) entering a standby mode upon completion of the write operation in response to the AUDPD configuration bit being cleared.

2. The method of claim 1 , wherein the low impedance output from the memory device is configured to indicate to the host that the memory device is in the UDPD mode by transition from a high impedance state.

3. The method of claim 1 , wherein the memory device drives the low impedance output regardless of a UDPD indicator bit state in the status register.

4. The method of claim 1 , further comprising exiting the UDPD mode in response to receiving a reset sequence from the host.

5. The method of claim 1 , wherein the host is configured to enter a sleep state upon issuing the write command to the memory device with the AUDPD configuration bit being set in the memory device.

6. The method of claim 1 , further comprising:

a) clearing, by the memory device, the AUDPD configuration bit after automatically entering the UDPD mode; and

b) setting, by a command from the host, the AUDPD configuration bit prior to a new write command when the UDPD mode is to automatically be entered following the new write command.

7. The method of claim 1 , further comprising:

a) receiving a command from the host to clear the AUDPD configuration bit;

b) receiving a plurality of page write commands from the host; and

c) receiving, prior to executing a last of the plurality of page write commands, a command from the host to set the AUDPD configuration bit.

8. The method of claim 1 , wherein a supply current of the memory device when in the UDPD mode is less than a supply current of the memory device when in the standby mode.

9. A memory device, comprising:

a) a command decoder configured to detect a write operation that is to be executed on the memory device in response to a write command issued by a host via an interface;

b) a write controller configured to execute the write operation;

c) a status register having an auto ultra-deep power down (AUDPD) configuration bit;

d) a controller configured to automatically enter a UDPD mode upon completion of the write operation in response to the AUDPD configuration bit being set;

e) an output circuit configured to drive a low impedance output from the memory device in response to a read status register command being received from the host while the memory device is in the UPDP mode; and

f) the controller being configured to enter a standby mode upon completion of the write operation in response to the AUDPD configuration bit being cleared.

10. The memory device of claim 9 , wherein the low impedance output from the memory device is configured to indicate to the host that the memory device is in the UDPD mode by transition from a high impedance state.

11. The memory device of claim 9 , wherein the memory device is configured to drive the low impedance output regardless of a UDPD indicator bit state in the status register.

12. The memory device of claim 9 , being configured to exit the UDPD mode in response to receiving a reset sequence from the host.

13. The memory device of claim 9 , wherein the host is configured to enter a sleep state upon issuing the write command to the memory device with the AUDPD configuration bit being set in the memory device.

14. The memory device of claim 9 , wherein the AUDPD configuration bit is configured to be:

a) cleared by the memory device after automatically entering the UDPD mode; and

b) set, by a command from the host, prior to a new write command when the UDPD mode is to automatically be entered following the new write command.

15. The memory device of claim 9 , wherein the interface comprises a serial peripheral interface (SPI).

16. The memory device of claim 9 , wherein a supply current of the memory device when in the UDPD mode is less than a supply current of the memory device when in the standby mode.

17. A method of controlling an ultra-deep power down (UDPD) mode in a memory device, the method comprising:

a) reading a UDPD indicator bit from a status register on the memory device;

b) reading an auto-UDPD (AUDPD) configuration bit from the status register;

c) determining that the memory device is in a standby mode when the UDPD indicator bit and the AUDPD configuration bit are both cleared;

d) receiving a low impedance output from the memory device in response to reading the status register while the memory device is in the UPDP mode;

e) issuing a reset sequence to the memory device in order to exit from the UDPD mode in response to the UDPD indicator bit being set as indicated by the low impedance output from the memory device; and

f) reading the status register in response to the UDPD indicator bit being cleared and the AUDPD configuration bit being set.

18. The method of claim 17 , wherein the low impedance output from the memory device is configured to indicate that the memory device is in the UDPD mode by transition from a high impedance state.

19. The method of claim 17 , further comprising:

a) reading, after issuing the reset sequence, the UDPD indicator bit; and

b) determining that the memory device is in the standby mode when the UDPD indicator bit is cleared.

20. The method of claim 19 , further comprising reading the status register in response to the UDPD indicator bit being set.