Datasheet

LTC6946
19
6946fa
OPERATION
Addr0 + Rd DON’T CARE
Hi-Z Hi-Z
MASTER–CS
MASTER–SDI
LTC6946–SDO
6946 F13
Byte 0 Byte 1 Byte 2
Figure 13. Serial Port Auto-Increment Read
beginning with data from register Addr0. The part ignores
all other data on SDI until the end of the burst.
Multidrop Configuration
Several LTC6946s may share the serial bus. In this multidrop
configuration, SCLK, SDI, and SDO are common between
all parts. The serial bus master must use a separate CS
for each LTC6946 and ensure that only one device has
CS asserted at any time. It is recommended to attach a
high value resistor to SDO to ensure the line returns to a
known level during Hi-Z states.
Serial Port Registers
The memory map of the LTC6946 may be found in Table 10,
with detailed bit descriptions found in Table 11. The register
address shown in hexadecimal format under the ADDR
column is used to specify each register. Each register is
denoted as either read-only (R) or read-write (R/W). The
register’s default value on device power-up or after a reset
is shown at the right.
The read-only register at address h00 is used to determine
different status flags. These flags may be instantly output
on the STAT pin by configuring register h01. See the STAT
Output section for more information.
The read-only register at address h0B is a ROM byte for
device indentification.
Table 10. Serial Port Register Contents
ADDR MSB [6] [5] [4] [3] [2] [1] LSB R/W DEFAULT
h00 * * UNLOCK ALCHI ALCLO LOCK THI TLO R
h01 * * x[5] x[4] x[3] x[2] x[1] x[0] R/W h04
h02 PDALL PDPLL PDVCO PDOUT PDREFO MTCAL OMUTE POR R/W h0E
h03 BD[3] BD[2] BD[1] BD[0] * * RD[9] RD[8] R/W h30
h04 RD[7] RD[6] RD[5] RD[4] RD[3] RD[2] RD[1] RD[0] R/W h01
h05 ND[15] ND[14] ND[13] ND[12] ND[11] ND[10] ND[9] ND[8] R/W h00
h06 ND[7] ND[6] ND[5] ND[4] ND[3] ND[2] ND[1] ND[0] R/W hFA
h07 ALCEN ALCMON ALCCAL ALCULOK * * CAL LKEN R/W h21
h08 BST FILT[1] FILT[0] RFO[1] RFO[0] OD[2] OD[1] OD[0] R/W hF9
h09 LKWIN[1] LKWIN[0] LKCT[1] LKCT[0] CP[3] CP[2] CP[1] CP[0] R/W h9B
h0A CPCHI CPCLO CPMID CPINV CPWIDE CPRST CPUP CPDN R/W hE4
h0B REV[2] REV[1] REV[0] PART[4] PART[3] PART[2] PART[1] PART[0] R hxx
†
*unused
†
varies depending on version