1840 查看數據表（PDF） - Linear Technology
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1840 Datasheet PDF : 12 Pages
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LTC1840
PI FU CTIO S
BLAST (Pin 13): Blast/Timer Function Input. This is a
multifunction digital input pin that controls blast and timer
operation. If this pin is in a logic high state at power-up or
is transitioned from high to low, it will “blast” the current
DAC outputs to full scale (100µA) no matter what their
previous state was and set a fault condition. In addition, if
BLAST is in a logic high state, the serial access timer is
active; this circuit measures time between serial commu-
nications to the LTC1840 and forces a blast and trips a fault
if the part hasn’t been accessed for about 1.5 minutes. This
pin has a 1V logic threshold.
IDACOUTB (Pin 14): Current DAC Output B. This is a high
impedance output with a sinking current output of 0µA to
100µA. This current can be programmed to one of 256
values through the serial interface or it can be “blasted”
immediately to full scale using the BLAST pin or by the
serial access timer if it is enabled and the LTC1840 is not
accessed for about 1.5 minutes. This pin will maintain the
programmed current to a very tight tolerance from as low
as 1.1V to at least 0.75V above VCC. The current DAC is
guaranteed to be monotonic over its full 8-bit range.
IDACOUTA (Pin 15): Current DAC Output A. See IDACOUTB
VCC (Pin 16): Positive Supply. This pin must be closely
decoupled to ground (pin 8). A 10µF tantalum and a 0.1µF
ceramic capacitor in parallel are recommended.
BLOCK DIAGRA
SCL 1
SERIAL
INTERFACE
IDACOUTA IDACOUTB
15
14
I
I
8-BIT
IDACs
FAULT
5
BLAST
13
FAULT
DETECT
GPI/O
INTERFACE
6 GPIO1
7 GPIO2
SDA 2
8-BIT
COUNTER
A1 3
A0 4
REF
8
GND
WU
W
TI I G DIAGRA
OSC
÷ 2, 4,
8, 16
8-BIT
COUNTER
12
TACHB
11
TACHA
SDA
tLOW
tsu, DAT
thD, DAT
SCL
thD, STA
tHIGH
tr
tf
START
CONDITION
tsu, STA
thD, STA
REPEATED START
CONDITION
6
9 GPIO3
10 GPIO4
1840 BD
tBUF
tsu, STO
STOP
CONDITION
1840 TD01
START
CONDITION
1840f
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