Rainbow Electronics DS3501 - Manual (Page 8)

DS3501
High-Voltage, NV, I 2 C POT with Temp Sensor
and Lookup Table
8 _____________________________________________________________________
LUT Mode
LUT Mode is selected by setting the Update Mode bit
(CR1.0) to 1 and the Adder Mode bit (CR1.1) to 0. An
overview of the DS3501 in this mode is illustrated in the
LUT Mode and LUT Adder Mode Block Diagram. Also,
the memory map for LUT Mode and LUT Adder Mode is
shown in Table 3. The major difference between the two
LUT modes is whether or not the value in the IVR is
added to the values stored in the lookup table. The
dashed line/arrow shown in the block diagram is not
active in LUT mode.
When in LUT Mode, on power-up the IVR value is
recalled into the WR register. This value will remain
there until completion of the first temperature conver-
sion following power-up. The temperature is measured
every t FRAME . The temperature value is used to calcu-
late an index that points to the corresponding value in
the lookup table. This index is referred to as the LUT
Address Register (LUTAR). The value stored in the LUT
at the location pointed to by LUTAR is called LUTVAL.
The Wiper Register is then automatically loaded with
LUTVAL. The process then repeats itself, continuously
updating the wiper setting in a closed-loop fashion.
In this mode the 36-byte LUT is populated with wiper
settings for each four-degree temperature window.
Valid wiper settings are 00h to 7Fh. The memory map in
Table 3 shows the memory address of the LUT as well
as the corresponding temperature range for each byte
in the LUT. Also, the LUT features one-degree hystere-
sis to prevent chattering if the measured temperature
REGISTER NAME
ADDRESS
(HEX)
VOLATILE/NONVOLATILE
FACTORY/POWER-UP
DEFAULT
WR/IVR Wiper Register/Initial Value 00h* NV (Shadowed) 40h
CR0 Control Register 0 02h V 00h
CR1 Control Register 1 03h NV (Shadowed) 00h
CR2 Control Register 2 0Ah V 00h
Table 2. Default Mode Memory Map
* In Default Mode, both WR and IVR are accessed through memory location 00h. Refer to the Default Mode section for additional information.
REGISTER NAME
ADDRESS
(HEX)
VOLATILE/NONVOLATILE
FACTORY/POWER-UP
DEFAULT
IVR Initial Value Register 00h* NV (Shadowed) 40h
CR0 Control Register 0 02h V 00h
CR1 Control Register 1 03h NV (Shadowed) 00h
LUTAR LUT Address Register 08h V N/A
WR Wiper Register 09h* V N/A
CR2 Control Register 2 0Ah V 00h
TEMP Temperature Value 0Ch V (Read-Only) N/A
VCC V CC Voltage Value 0Eh V (Read-Only) N/A
LUT0 Wiper Value for T ≤ -37°C 80h NV 00h
LUT1 Wiper Value for -36°C to -33°C 81h NV 00h
LUT2 Wiper Value for -32°C to -29°C 82h NV 00h
— — — — —
LUT33 Wiper Value for +92°C to +95°C A1h NV 00h
LUT34 Wiper Value for +96°C to +99°C A2h NV 00h
LUT35 Wiper Value for T ≥ 100°C A3h NV 00h
Table 3. LUT Mode and LUT Adder Mode Memory Map
* In LUT Mode and LUT Adder Mode, the WR is accessed through memory address 09h, while IVR remains at memory address 00h.