LTC1857/LTC1858/LTC1859
PIN FUNCTIONS
DGND (Pin 24): Digital Ground.
SDI (Pin 25): Serial Data Input. SDI will ignore clocked
data while RD is high.
SCK (Pin 26): Serial Data Clock.
RD (Pin 27): Read Input. This active low signal enables
the digital output pin SDO.
CONVST (Pin 28): Conversion Start. This active high signal
starts a conversion on its rising edge.
FUNCTIONAL BLOCK DIAGRAM
AVDD DVDD
CH0
CH1
•
INPUT MUX
•
AND
RANGE
•
SELECT
CH7
COM
MUX ADDRESS AND RANGE
INTERNAL
CLOCK
CONTROL
LOGIC
+
12-/14-/16-BIT
SAMPLING ADC
–
DATA OUT
2.5V
REFERENCE
8k
4.096V
1.6384X
SERIAL I/O
CONVST
SDI
BUSY
SCK
RD
OVDD
SDO
MUXOUT–
AGND1
MUXOUT+ ADC+
ADC–
VREF
REFCOMP
1859 BD
AGND2 AGND3 DGND
TEST CIRCUITS
Load Circuits for Access Timing
5V
DN
1k
25pF
1k
DN
25pF
(A) Hi-Z TO VOH AND VOL TO VOH
(B) Hi-Z TO VOL AND VOH TO VOL
1859 TC01
Load Circuits for Output Float Delay
5V
DN
1k
1k
DN
25pF
25pF
(A) VOH TO Hi-Z
(B) VOL TO Hi-Z
1859 TC02
185789fb
8
For more information www.linear.com/LTC1857