LTC1098 LINER [Linear Technology], LTC1098 Datasheet - Page 26

• Manufacturer Part Number: LTC1098
• Description: Micropower Sampling 8-Bit Serial I/O A/D Converters
• Manufacturer: LINER [Linear Technology]

LTC1096/LTC1096L
LTC1098/LTC1098L
Remote or Isolated Systems
Figure 16 shows a floating system that sends data to a
grounded host system. The floating circuitry is isolated by
two optoisolators and powered by a simple capacitor
diode charge pump. The system has very low power
requirements because the LTC1096 shuts down between
26
TYPICAL
Figure 16. Power for This Floating A/D System Is Provided by a Simple Capacitor Diode Charge Pump. The Two Optoisolators
Draw No Current Between Samples, Turning On Only to Send the Clock and Receive Data
DATA
CLK
A
300
500k
PPLICATI
10k
5MHz
0.001 F
2kV
O
100k
U
1N5817
1N5817
S
2N3904
+
0.022 F
47 F
FLOATING SYSTEM
conversions and the optoisolators draw power only when
data is being transferred. The system consumes only
50 A at a sample rate of 10Hz (1ms on-time and 99ms off-
time). This is easily within the current supplied by the
charge pump running at 5MHz. If a truly isolated system
is required, the system’s low power simplifies generating
an isolated supply or powering the system from a battery.
100k
1N5817
0.1 F
20k
CS
CLK
LTC1096
GND
V
CC
D
V
+IN
–IN
OUT
REF
ANALOG
INPUT
1k
75k
LT1004-2.5
LTC1096/8 • F16