MAX1359B Maxim Integrated Products, MAX1359B Datasheet - Page 58

• Manufacturer Part Number: MAX1359B
• Description: Data-Acquisition System
• Manufacturer: Maxim Integrated Products

DataSheet.in
16-Bit, Data-Acquisition System with ADC, DAC,
UPIOs, RTC, Voltage Monitors, and Temp Sensor
Exit sleep mode and enter normal mode by one of the
following methods:
• With the SHDN bit = 0, deassert the SLEEP or
• With the SLEEP or SLEEP function deasserted on
• With the SLEEP or SLEEP function deasserted,
• With the SLEEP or SLEEP function deasserted, the
A wake-up event, such as an assertion of a UPIO con-
figured as WU or a time-of-day alarm causes the
MAX1359B to exit sleep mode, if in sleep mode. A
wake-up event in normal mode results only in a wake-
up event being recorded in the STATUS register.
The RESET output pulls low for any one of the following
cases: power-on reset, DV
0, watchdog timer expires, crystal oscillator is attached,
and 32kHz clock not ready.
The RESET output can be turned off through the RSTE
bit in the PS_VMONS register, causing DV
ply voltage events to issue an interrupt or poll through
the LDVD status bit. This allows brownout detection
µCs that operate with DV
UPIO outputs can be driven to AV
with separate AV
charge-pump doubler by setting CPE = 0 in the
PS_VMONS register, and connect the system’s analog
supply to AV
drive to CPOUT results in AV
The AV
ADC by reversing the normal input and reference sig-
nals. The REF voltage is applied to one multiplexer
input and AGND is selected in the other. The AV
nal is then switched in as the ADC reference voltage
and a conversion is performed. The AV
then be calculated directly as:
where V
is the PGA gain before the ADC, and N is the ADC
result. Note the AV
58
SLEEP function on UPIO, only if SLEEP or SLEEP
function is used for entering sleep mode.
UPIO, clear the SHDN bit by writing to the normal-
mode register address control byte.
assert WU or WU (wake-up) function on UPIO.
day alarm triggers.
______________________________________________________________________________________
Driving UPIO Outputs to AV
DD
REF
V
supply voltage can be measured with the
AVDD
is the reference voltage for the ADC, Gain
DD
and CPOUT. Setting UPIO outputs to
Supply Voltage Measurement
= (V
DD
DD
and DV
REF
voltage must be greater than the
DD
x Gain x 65536) / N
DD
< 1.8V.
DD
DD
monitor trips and RSTE =
-referenced logic levels.
supplies. Disable the
DD
levels in systems
DD
DD
DD
Wake-Up
value can
low sup-
Levels
RESET
DD
sig-
gained-up REF voltage (AV
measurement must be done in unipolar mode.
AV
AV
powers up the digital section. The power supply for both
AV
AV
operation. AV
power supply. Bypass AV
trolytic capacitor in parallel with a 0.1µF ceramic capaci-
tor and bypass DV
capacitor in parallel with a 0.1µF ceramic capacitor. For
improved performance, place the bypass capacitors as
close to the device as possible.
Figures 20 and 21 provide the ADC transfer functions
for unipolar and bipolar mode. The digital output code
format is binary for unipolar mode and two’s comple-
ment for bipolar mode. Calculate 1 LSB using the fol-
lowing equations:
where V
Gain equals the PGA gain.
In unipolar mode, the output code ranges from 0 to
65,535 for inputs from zero to full-scale. In bipolar
mode, the output code ranges from -32,768 to +32,767
for inputs from negative full-scale to positive full-scale.
Figure 20. ADC Unipolar Transfer Function
DD
DD
DD
DD
1 LSB (Bipolar Mode) = ±2V
1 LSB (Unipolar Mode) = V
1111 1111 1111 1111
1111 1111 1111 1110
1111 1111 1111 1101
1111 1111 1111 1100
0000 0000 0000 0011
0000 0000 0000 0010
0000 0000 0000 0001
0000 0000 0000 0000
and DV
and DV
powers up the analog section, while the DV
and DV
REF
equals the reference voltage at REF and
DD
DD
DD
DD
0
1 LSB =
must be greater than +1.8V for device
provide power to the MAX1359B. The
and DV
1
ranges from +1.8V to +3.6V. Both
DD
2
(GAIN x 65,536)
to DGND with a 10µF electrolytic
3
V
REF
ADC Transfer Functions
DD
DD
INPUT VOLTAGE (LSB)
FULL-SCALE TRANSITION
DD
to AGND with a 10µF elec-
can connect to the same
V
REF
REF
REF
> V
/GAIN
/ (Gain x 65,536)
Power Supplies
/ (Gain x 65,536)
REF
65,533
x GAIN). This
65,535
DD