Datasheet

DS3514
I
2
C Gamma and V
COM
Buffer with EEPROM
12 ______________________________________________________________________________________
Map , the Latch A registers for each channel are
accessed through memory addresses 00–1Ch. Then,
like the other modes, the LD pin determines when the
DACs are updated. If the LD signal is high, Latch B is
flow-through and the DAC is updated immediately. If
LD is low, Latch B is loaded from Latch A after a low-to-
high transition on the LD pin. This latter method allows
the timing of the DAC update to be controlled by an
external signal pulse.
V
COM
/Gamma Channel Outputs
As illustrated in the Block Diagram , the gamma channel
outputs are equivalent to a 10-bit digital potentiometer
(DAC) with a buffered output. The V
COM
channel is
equivalent to an 8-bit digital potentiometer (DAC) with a
buffered output. The V
COM
channel’s digital poten-
tiometer is composed of 255 equal resistive elements.
The relationship between output voltage and DAC set-
ting is illustrated in Table 3a. Unlike the gamma chan-
nels, the V
COM
channel is capable of outputting a
range of voltages including both references (VRH and
VRL). Each of the gamma channel digital potentiome-
ters, on the other hand, are composed of 1024 equal
resistive elements. The extra resistive element prohibits
one of the rails from being reached. In particular,
gamma channel outputs GM1–GM7 can span from
(and including) GLL to 1 LSB away from GLM.
Likewise, gamma channel outputs GM8–GM14 span
from (and including) GHM to 1 LSB away from GHH.
The relationship between output voltage and DAC set-
ting for the gamma channels are also illustrated in
Table 3b.
Standby Mode
Standby mode (not to be confused with the three
DS3514 operating modes) can be used to minimize
current consumption. Standby mode is entered by set-
ting the STANDBY bit, which is the MSB of register 41h.
The V
COM
and gamma outputs are placed in a high-
impedance state. Current drawn from the V
DD
supply in
this state is specified as I
DDQ
.
The DS3514 continues to respond to I
2
C commands,
and thus draws some current from V
CC
when I
2
C activi-
ty is occurring. When the I
2
C interface is inactive, cur-
rent drawn from the V
CC
supply is specified as I
CCQ
.
Thermal Shutdown
As a safety feature, the DS3514 goes into a thermal
shutdown state if the junction temperature ever reaches
SETTING
(HEX)
V
COM
OUTPUT VOLTAGE
00h VRL
01h VRL + (1/255) x (VRH - VRL)
02h VRL + (2/255) x (VRH - VRL)
03h VRL + (3/255) x (VRH - VRL)
0Fh VRL + (15/255) x (VRH - VRL)
3Fh VRL + (63/255) x (VRH - VRL)
7Fh VRL + (127/255) x (VRH - VRL)
FDh VRL + (253/255) x (VRH - VRL)
FEh VRL + (254/255) x (VRH - VRL)
FFh VRH
Table 3a. V
COM
DAC Voltage/Data
Relationship for Selected Codes
Table 3b. Gamma DAC Voltage/Data Relationship for Selected Codes
SETTING
(HEX)
GM1–GM7 OUTPUT VOLTAGE GM8–GM14 OUTPUT VOLTAGE
000h GLM + (0 + 1) x ((GLL - GLM)/1024) GHM + (0 + 1) x ((GHH - GHM)/1024)
001h GLM + (1 + 1) x ((GLL - GLM)/1024) GHM + (1 + 1) x ((GHH - GHM)/1024)
002h GLM + (2 + 1) x ((GLL - GLM)/1024) GHM + (2 + 1) x ((GHH - GHM)/1024)
003h GLM + (3 + 1) x ((GLL - GLM)/1024) GHM + (3 + 1) x ((GHH - GHM)/1024)
00Fh GLM + (15 + 1) x ((GLL - GLM)/1024) GHM + (15 + 1) x ((GHH - GHM)/1024)
03Fh GLM + (63 + 1) x ((GLL - GLM)/1024) GHM + (63 + 1) x ((GHH - GHM)/1024)
07Fh GLM + (127 + 1) x ((GLL - GLM)/1024) GHM + (127 + 1) x ((GHH - GHM)/1024)
0FFh GLM + (255 + 1) x ((GLL - GLM)/1024) GHM + (255 + 1) x ((GHH - GHM)/1024)
3FDh GLM + (1021 + 1) x ((GLL - GLM)/1024) GHM + (1021 + 1) x ((GHH - GHM)/1024)
3FEh GLM + (1022 + 1) x ((GLL - GLM)/1024) GHM + (1022 + 1) x ((GHH - GHM)/1024)
3FFh GLL GHH