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

shouldbeprogrammedassoonaspossibleafterthepower

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.