The AS1545 is a dual, 12-bit, 6-channel, 1 MSPS, high
speed, successive approximation (SAR) analog-to-
digital converters (ADCs). The AS1545 is designed to
operate with a single +2.7V to +5.25V supply and a
sampling rate of up to 1 MSPS.
The device contains two ADCs, each preceded by a 6-
channel multiplexer and a high-bandwidth track/hold
amplifier. Data access is made via standard control
inputs in support of wide range of microprocessors and
DSPs.
The device requires very low supply-current at the
1MSPS maximum sampling speed, and features flexible
power-down modes to reduce power consumption at
slower throughput rate.
The AS1545 contains an internal 2.5V reference and
integrated reference buffer that can be over driven when
an external reference is required.
Superior AC characteristics, low power consumption,
and highly reliable packaging makes the AS1545 perfect
for portable battery-powered remote sensors and data-
acquisition devices.
The AS1545 is available in a 32-lead TQFN package.
2 Key Features
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Sampling Rate: 1MSPS per ADC
Dual 12-bit serial interface
Software Configurable Analog Input Types:
- 12-Channel Single-Ended
- 6-Channel Pseudo-Differential
- 6-Channel Fully Differential
Internal +2.5V Reference or External: 1V to V
DD
Rail to Rail Common Mode Input Range
Low-Power Consumption
- 15mW max. at 1MSPS with 2.7V supplies
- 37mW max. at 1MSPS with 5.25V supplies
Dual conversion with read at 20 MHz SCLK
Single-Supply Operation: +2.7V to +5.25V
Motor Control Registers: Difference of Inputs,
Quadrature Signal Phases, Direction and Step
Down Counter
32-lead TQFN Package
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3 Applications
The device is ideal for motor control like encoder feed-
back or current sense, motion control such as robotics,
sonar, or for any other radio frequency identification.
Figure 1. AS1545 - Block Diagram
REF_SELECT
REF
AIN 0
AIN 1
AIN 2
AIN 3
AIN 4
AIN 5
Control Logic
and
System Control
Registers
BIN 0
BIN 1
BIN 2
BIN 3
BIN 4
BIN 5
BUF
AGND
AGND
AGND
REFB
MUX
T/H
12-Bit
SAR and A/D
Conversion
Control
OutPut
Drivers
MUX
T/H
BUF
REFA
AVDD
DVDD
System
Control
Registers
12-Bit
SAR and A/D
Conversion
Control
OutPut
Drivers
DOUTA
SCLK
CSN
RANGE
SGL/DIFF
A0
A1
A2
VDRIVE
DOUTB
AS1545
DGND
DGND
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Revision 1.01
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AS1545
Datasheet
Contents
1
2
3
4
General Description ................................................................................................................................................
Key Features ...........................................................................................................................................................
Absolute Maximum Ratings .................................................................................................................................... 5
Analog Input .......................................................................................................................................................
Acquisition Time ............................................................................................................................................
Analog Input Composition .............................................................................................................................
Analog Input Modes ......................................................................................................................................
Transfer Functions ........................................................................................................................................
Digital Inputs ......................................................................................................................................................
10 Application Information .......................................................................................................................................
Full Power-Up Mode ..................................................................................................................................... 25
Full Power-Down Mode ................................................................................................................................. 25
Power-Up Times ........................................................................................................................................... 27
Power vs. Throughput Rate .......................................................................................................................... 28
Serial Interface ................................................................................................................................................... 28
Difference calculator and quadrature signals calculator ................................................................................ 29
Direction of the rotor based on DIR bit .......................................................................................................... 30
Grounding and Layout ................................................................................................................................... 31
PCB Design Guidelines for TQFN ................................................................................................................. 31
12 Package Drawings and Markings ........................................................................................................................ 32
13 Ordering Information ........................................................................................................................................... 33
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Revision 1.01
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AS1545
Datasheet - P i n o u t
4 Pinout
Pin Assignment
Figure 2. Pin Assignments (Top View)
VDRIVE
DOUTA
DOUTB
DGND
DVDD
SCLK
CSN
32
DGND
1
31 30
29
28 27 26
25
24
23
22
A1
A2
SGL/DIFF
REF_SELECT 2
AVDD
REFA
AGND
AGND
AIN 0
AIN 1
3
4
5
6
7
8
9
AIN 2
10
AIN 3
11 12
AIN 4
AIN 5
13 14 15 16
BIN 5
BIN 4
BIN 3
BIN 2
33 Exp. Pad
AS1545
A0
21 RANGE
20
19
18
17
REFB
AGND
BIN 0
BIN 1
Pin Description
Table 1. Pin Description
Pin Number
1, 29
Pin Name
DGND
Description
Digital Ground.
Ground reference point for the digital portion of the
AS1545.
Reference select pin.
Internal/External Reference Selection. Logic input. If
this pin is tied to DGND, the on-chip 2.5V reference is used as the reference
source for both ADC A and ADC B. In addition, Pin REFA and Pin REFB
must be tied to decoupling capacitors. If the REF SELECT pin is tied to a
logic high, an external reference can be supplied to the AS1545 through the
REF
A
or REF
B
pins.
Analog Supply Voltage.
2.7V to 5.25V.
Reference Input/Output.
These pins are connected to the internal
reference through a series resistor and is the reference source for the
AS1545. The nominal reference voltage is 2.5V and appears at the pin. This
pin can be over-driven by an external reference or can be taken as high as
AV
DD
. Decoupling capacitors (4.7 uF recommended) are connected to
these pins to decouple the reference buffer for each respective ADC.
Analog Ground.
Decouple point for AV
DD
. Ground reference for track/hold,
reference, and DAC circuits.
Analog Ground.
Decouple point for V
REF
capacitors and analog input
filters. Pin 6 is the decoupling point for REFA, pin 19 for REFB. Ground
reference for track/hold, reference, and DAC circuits.
Analog Inputs of ADC A.
These may be programmed as six single-ended
channels, three pseudo-differential or three true-differential analog input
channel pairs.
2
REF_SELECT
3
AV
DD
4, 20
REF
A
, REF
B
5
AGND
6, 19
AGND
7 to 12
AIN0 to AIN5
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Revision 1.01
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AS1545
Datasheet - P i n o u t
Table 1. Pin Description
Pin Number
13 to 18
Pin Name
BIN0 to BIN5
Description
Analog Inputs of ADC B.
These may be programmed as six single-ended
channels, three pseudo-differential or three true-differential analog input
channel pairs.
(see Table 5 on page 20).
Analog Input Range Selection.
Logic input. The polarity on this pin
determines the input range of the analog input channels. If this pin is tied to
a logic low, the analog input range is 0V to V
REF
. If this pin is tied to a logic
high when CSN goes low, the analog input range is 2 × V
REF
.
Logic Input.
This pin selects whether the analog inputs are configured as
differential pairs or single ended. A logic low selects differential operation
while a logic high selects single-ended operation.
Multiplexer Select.
Logic inputs. These inputs are used to select the pair of
channels to be simultaneously converted, such as Channel 1 of both ADC A
and ADC B, Channel 2 of both ADC A and ADC B, and so on.
Chip Select.
Active low logic input. This input provides the dual function of
initiating conversions on the AS1545 and framing the serial data transfer.
Serial Clock Input.
A serial clock input provides the SCLK for accessing the
data from the AS1545. This clock is also used as the clock source for the
conversion process.
Serial Data Outputs.
The data output is supplied to each pin as a serial
data stream. The bits are clocked out on the falling edge of the SCLK input
and 15 SCLKs are required to access the data. The data simultaneously
appears on both pins from the simultaneous conversions of both ADCs. The
data stream consists of three leading zeros followed by the 12 bits of
conversion data. The data is provided MSB first. If CSN is held low for 16
SCLK cycles rather than 15, then single trailing zero appears after the 12bits
of data. If CSN is held low for a further 16 SCLK cycles on either D
OUTA
or
D
OUTB
, futher data is clocked out according to the timing diagram.
Logic Power Supply Input.
The voltage supplied at this pin determines at
what voltage the interface operates. This pin should be decoupled to DGND.
The voltage at this pin may be different than that at AV
DD
and DV
DD
but
should never exceed either by more than 0.3V.
Digital Supply Voltage.
2.7V to 5.25V. This is the supply voltage for all
digital circuitry on the AS1545. The DV
DD
and AV
DD
voltages should ideally
be at the same potential and must not be more than 0.3V apart even on a
transient basis. This supply should be decoupled to DGND.
Exposed Pad.
This pin can be not connected or connected AGND. The
exposed pad must not be connected to V
DD
.
21
RANGE
22
SGL/DIFF
23 to 25
A2 to A0
26
CSN
27
SCLK
28, 30
D
OUTB
, D
OUTA
31
V
DRIVE
32
DV
DD
33
Exp. Pad
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Revision 1.01
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AS1545
Datasheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Stresses beyond those listed in
Table 2
may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond those indicated in
Electrical
Characteristics on page 6
is not implied. Exposure to absolute maximum rating conditions for extended periods may
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