MAX1090BEEI Maxim Integrated, MAX1090BEEI Datasheet - Page 15

• Manufacturer Part Number: MAX1090BEEI
• Description: Analog to Digital Converters - ADC
• Manufacturer: Maxim Integrated

Specifications of MAX1090BEEI

• Number Of Channels: 8/4
• Architecture: SAR
• Conversion Rate: 400 KSPs
• Resolution: 10 bit
• Input Type: Single-Ended/Pseudo-Differential
• Snr: Yes
• Interface Type: Parallel
• Operating Supply Voltage: 2.7 V to 5.5 V, 5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: QSOP-28
• Maximum Power Dissipation: 667 mW
• Minimum Operating Temperature: - 40 C
• Number Of Converters: 1
• Voltage Reference: Internal 2.5 V or External

___________Applications Information
When power is first applied, internal power-on reset cir-
cuitry activates the MAX1090/MAX1092 in external
clock mode and sets INT high. After the power supplies
stabilize, the internal reset time is 10µs, and no conver-
sions should be attempted during this phase. When
using the internal reference, 500µs are required for
V
The MAX1090/MAX1092 can be used with an internal
or external reference voltage. An external reference
can be connected directly to REF or REFADJ.
An internal buffer is designed to provide +2.5V at REF
for both devices. The internally trimmed +1.22V refer-
ence is buffered with a +2.05V/V gain.
The full-scale range with the internal reference is +2.5V
with unipolar inputs and ±1.25V with bipolar inputs. The
internal reference buffer allows for small adjustments
(±100mV) in the reference voltage (Figure 7).
Note: The reference buffer must be compensated with an
external capacitor (4.7µF min) connected between REF
and GND to reduce reference noise and switching spikes
from the ADC. To further minimize reference noise, con-
nect a 0.01µF capacitor between REFADJ and GND.
With the MAX1090/MAX1092, an external reference can
be placed at either the input (REFADJ) or the output
(REF) of the internal reference-buffer amplifier.
Table 5. Data-Bus Output (8 + 2 Parallel
Interface)
REF
PIN
D0
D1
D2
D3
D4
D5
D6
D7
to stabilize.
Bit 0 (LSB)
HBEN = 0
with +2.5V Reference and Parallel Interface
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
Internal and External Reference
______________________________________________________________________________________
400ksps, +5V, 8-/4-Channel, 10-Bit ADCs
Bit 8
Bit 9 (MSB)
(UNI/BIP = 0)
BIPOLAR
Bit 9
Bit 9
Bit 9
Bit 9
Bit 9
Bit 9
HBEN = 1
Power-On Reset
External Reference
Internal Reference
(UNI/BIP = 1)
UNIPOLAR
0
0
0
0
0
0
Using the REFADJ input makes buffering the external
reference unnecessary. The REFADJ input impedance
is typically 17kΩ.
When applying an external reference to REF, disable
the internal reference buffer by connecting REFADJ to
V
Therefore, an external reference at REF must deliver up
to 200µA DC load current during a conversion and
have an output impedance less than 10Ω. If the refer-
ence has higher output impedance or is noisy, bypass
it close to the REF pin with a 4.7µF capacitor.
To save power, place the converter in a low-current
shutdown state between conversions. Select standby
mode or shutdown mode using bits D6 and D7 of the
control byte (Tables 1 and 2). In both software power-
down modes, the parallel interface remains active, but
the ADC does not convert.
While in standby mode, the supply current is 1mA (typ).
The part powers up on the next rising edge on WR and
is ready to perform conversions. This quick turn-on time
allows the user to realize significantly reduced power
consumption for conversion rates below 400ksps.
Shutdown mode turns off all chip functions that draw
quiescent current, reducing the typical supply current
to 2µA immediately after the current conversion is com-
pleted. A rising edge on WR causes the MAX1090/
MAX1092 to exit shutdown mode and return to normal
operation. To achieve full 10-bit accuracy with a 4.7µF
reference bypass capacitor, 500µs is required after
power-up. Waiting 500µs in standby mode, instead of in
full-power mode, can reduce power consumption by a
factor of 3 or more. When using an external reference,
Figure 7. Reference Voltage Adjustment with External
Potentiometer
DD
50kΩ
50kΩ
V
. The DC input resistance at REF is 25kΩ.
DD
= +5V
GND
330kΩ
0.01µF
4.7µF
Power-Down Modes
Shutdown Mode
REFADJ
REF
Standby Mode
MAX1090
MAX1092
15