Datasheet

LTM9012
19
9012f
applicaTions inForMaTion
The SDO pin is an open-drain output that pulls to ground
with a 200Ω impedance. If register data is read back
through SDO, an external 2k pull-up resistor is required. If
serial data is only written and read back is not needed, then
SDO can be left floating and no pull-up resistor is needed.
Table 4 shows a map of the mode control registers.
Software Reset
If serial programming is used, the mode control registers
should be programmed as soon as possible after the power
supplies turn on and are stable. The first serial command
must be a software reset which will reset all register data
bits to logic 0. To perform a software reset, bit D7 in the
reset register is written with a logic 1. After the reset is
complete, bit D7 is automatically set back to zero.
Table 4. Serial Programming Mode Register Map (PAR/SER = GND)
REGISTER A0: RESET REGISTER (ADDRESS 00h) WRITE ONLY
D7 D6 D5 D4 D3 D2 D1 D0
RESET X X X X X X X
Bit 7 RESET Software Reset Bit
0 = Not Used
1 = Software Reset. All mode control registers are reset to 00h. The ADC is momentarily placed in Sleep mode.
This bit is automatically set back to zero at the end of the SPI Write command. The Reset register is Write only.
Data read back from the reset register will be random.
Bits 6-0 Unused, Don’t Care Bits.
REGISTER A1: FORMAT AND POWER-DOWN REGISTER (ADDRESS 01h with CS = GND)
D7 D6 D5 D4 D3 D2 D1 D0
DCSOFF RAND TWOSCOMP SLEEP NAP_4 NAP_3 NAP_2 NAP_1
Bit 7 DCSOFF Clock Duty Cycle Stabilizer Bit
0 = Clock Duty Cycle Stabilizer On
1 = Clock Duty Cycle Stabilizer Off. This is not recommended.
Bit 6 RAND Data Output Randomizer Mode Control Bit
0 = Data Output Randomizer Mode Off
1 = Data Output Randomizer Mode On
Bit 5 TWOSCOMP Two’s Complement Mode Control Bit
0 = Offset Binary Data Format
1 = Two’s Complement Data Format
Bits 4-0 SLEEP: NAP_X Sleep/Nap Mode Control Bits
00000 = Normal Operation
0XXX1 = Channel 1 in Nap Mode
0XX1X = Channel 2 in Nap Mode
0X1XX = Channel 3 in Nap Mode
01XXX = Channel 4 in Nap Mode
1XXXX = Sleep Mode. Channels 1, 2, 3 and 4 are Disabled
Note: Any combination of these channels can be placed in Nap mode.