SX8645I05AWLTRT Semtech, SX8645I05AWLTRT Datasheet - Page 21

• Manufacturer Part Number: SX8645I05AWLTRT
• Description: 12-ch Capacitive Touch Solution (Button & Wheel)
• Manufacturer: Semtech

SX8645
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (12 sensors) with Enhanced LED Drivers
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
Host NVM mode
Figure 20
The writing of the host towards the NVM is not done directly but done in 2 steps (Figure 20).
In the first step the host writes to the SPM (as in Figure 19). In the second step the host signals the SX8645 to
copy the SPM content into the NVM.
Initially the NVM memory is empty and it is required to determine a valid parameter set for the application. This
can be done during the development phase using dedicated evaluation hardware representing the final
application. This development phase uses probably initially the host SPM mode which allows faster iterations.
Once the parameter set is determined this can be written to the NVM over the I2C using the 2 steps approach by
the host or a dedicated programmer for large volumes production (as described in the paragraphs 6.6 and 6.7).
3.11 Power Management
The SX8645 uses on-chip voltage regulators which are controlled by the on-chip microprocessor. The regulators
need to be stabilized with an external capacitor between VANA and ground and between VDIG and ground (see
Table 5). Both regulators are designed to only drive the SX8645 internal circuitry and must not be loaded
externally.
3.12 Clock Circuitry
The SX8645 has its own internal clock generation circuitry that does not require any external components. The
clock circuitry is optimized for low power operation and is controlled by the on-chip microprocessor. The typical
operating frequency of the oscillating core is 16.7MHz from which all other lower frequencies are derived.
3.13 I2C interface
The I2C interface allows the communication between the host and the SX8645.
The I2C slave implemented on the SX8645 is compliant with the standard (100kb/s) and fast mode (400kb/s)
The default SX8645 I2C address equals 0b010 1011.
A different I2C address can be programmed by the user in the NVM.
Revision 7_5, February 10
© 2010 Semtech Corp.
www.semtech.com
21