Rainbow Electronics MAX1189 - Manual (Page 7)

Detailed Description
Converter Operation
The MAX1179/MAX1187/MAX1189 use a successive-
approximation (SAR) conversion technique with an
inherent track-and-hold (T/H) stage to convert an ana-
log input into a 16-bit digital output. Parallel outputs
provide a high-speed interface to microprocessors
(µPs). The Functional Diagram at the end of the data
sheet shows a simplified internal architecture of the
MAX1179/MAX1187/MAX1189. Figure 3 shows a typical
application circuit for the MAX1179/MAX1187/MAX1189.
Analog Input
Input Scaler
The MAX1179/MAX1187/MAX1189 have an input scaler
which allows conversion of true bipolar input voltages
and input voltages greater than the power supply, while
operating from a single +5V analog supply. The input
scaler attenuates and shifts the analog input to match
the input range of the internal DAC. The MAX1179 input
voltage range is ±5V, while the MAX1189 input voltage
range is ±10V. The MAX1187 has a unipolar input volt-
age range of 0 to +10V. Figure 4 shows the equivalent
input circuit of the MAX1179/MAX1187/MAX1189. This
circuit limits the current going into or out of AIN to less
than 1.8mA.
MAX1179/MAX1187/MAX1189
16-Bit, 135ksps, Single-Supply ADCs with
Bipolar Analog Input Range
_______________________________________________________________________________________ 7
Pin Description (continued)
PIN NAME FUNCTION
15 REFADJ
Reference Buffer Output. Bypass REFADJ with a 0.1µF capacitor to AGND for internal reference
mode. Connect REFADJ to AV
DD to select external reference mode.
16 REF
Reference Input/Output. Bypass REF with a 10µF capacitor to AGND. REF is the external reference
input when in external reference mode.
17 RESET Reset Input. Logic high resets the device.
18 CS
Convert Start. The first falling edge of CS powers up the device and enables acquisition when R/C
is low. The second falling edge of CS starts conversion. The third falling edge of CS loads the result
onto the bus when R/C is high.
19 DGND Digital Ground
20 DV DD Digital Supply Voltage. Bypass with a 0.1µF capacitor to DGND.
21 D0 Three-State Digital Data Output (LSB)
22 D1 Three-State Digital Data Output
23 D2 Three-State Digital Data Output
24 D3 Three-State Digital Data Output
25 D4 Three-State Digital Data Output
26 D5 Three-State Digital Data Output
27 D6 Three-State Digital Data Output
28 D7 Three-State Digital Data Output
Figure 1. Load Circuits
1mA
DGND
HIGH-Z TO V OH ,
V OL TO V OH , AND
V OH TO HIGH-Z
C LOAD = 20pF
D0–D15
A)
1mA
DV DD
DGND
HIGH-Z TO V OL ,
V OH TO V OL , AND
V OL TO HIGH-Z
C LOAD = 20pF
D0–D15
B)