ICmicTM ICmicTM - IC Microsystems

ICM7722
ICm ic
TM
IC M ICROSYSTEM S
FEATURES
12-Bit 1.2v Low Power Dual DAC
With Serial Interface and Voltage Output
OVERVIEW
• 12-Bit 1.2v Dual DAC in 8 Lead TSSOP
Package
• Ultra-Low Power Consumption
• Guaranteed Monotonic
• Wide Voltage Output Swing Buffer
• Three-wire SPI/QSPI and Micro-wire
Interface Compatible
• Schmitt-Triggered Inputs for Direct
Interfacing to opto-couplers
The ICM7722 is a 12-Bit Voltage Output, ultra
Low Power,
Dual DAC, with guaranteed
monotonic behavior. This DAC is available in
8- Lead TSSOP package.
The input interface is an easy to use three-wire
SPI, QSPI and Micro-wire compatible interface.
The DAC has Schmitt- Triggered inputs for
Direct Interfacing to opto-couplers easily.
BLOCK DIAGRAM
REFIN
APPLICATION
•
•
•
•
Battery-Powered Applications
Audio Applications
Industrial Process Control
Digital Gain and Offset Adjustment
ICM7722
VOA
INPUT
REGISTER A
DAC
REGISTER A
DAC A
INPUT
REGISTER B
DAC
REGISTER B
DAC B
AMPLIFIER
VOB
AMPLIFIER
INPUT CONTROL LOGIC, REGISTERS AND LATCHES
CS
Rev A1.5
SDI
ICmic reserves the right to change specifications without prior notice
SCK
1
ICM7722
PACKAGE
08 Lead TSSOP
SCK
1
8
VOA
SDI
2
7
VDD
CS
3
6
REFIN
GND
4
5
VOB
TOP VIEW
PIN DESCRIPTION (8 Lead TSSOP)
Pin
Name
I/O
Description
1
2
SCK
SDI
I
I
Serial Clock Input (CMOS)
Serial Data Input (CMOS)
3
CS
I
Active Low Chip Select (CMOS)
4
GND
I
Ground
5
VOB
O
DAC B Output Voltage
6
REFIN
I
Reference Voltage Input
7
VDD
I
Supply voltage
8
VOA
O
DAC A Output Voltage
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
VDD
Supply Voltage
IIN
Input Current
VIN
Digital Input Voltage (SCK, SDI, CS )
Value
Unit
0.9 to 1.32
V
+/- 25.0
mA
-0.3 to 1.32
V
VIN_REF
Reference Input Voltage
-0.3 to 1.32
V
TSTG
Storage Temperature
-65 to +150
oC
TSOL
Soldering Temperature
300
oC
Stress greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification
is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
Rev A1.5
ICmic reserves the right to change specifications without prior notice
2
ICM7722
ORDERING INFORMATION
Part
Operating Temperature Range
Package
-40 oC to 85 oC
08-Lead TSSOP
ICM7722
DC ELECTRICAL CHARACTERISTICS
(Specification: VDD=1.2V, VREFIN=1.15v, Temp=25°C, unless otherwise specified)
Symbol
Parameter
Test Conditions
Min
Typ
Max
Unit
DC PERFORMANCE
12
N
Resolution
Bits
DNL
Differential Nonlinearity
(Notes 1 & 3)
0.4
+1.0
LSB
INL
Integral Nonlinearity
(Notes 1 & 3)
1
+12
LSB
STATIC ACCURACY
GE
Gain Error
+0.5
% of FS
OE
Offset Error
25
mV
1.2
1.32
V
490
1000
µA
VDD
V
13
mA
POWER REQUIREMENTS
VDD
0.9
Supply Voltage
IDD
Supply Current
OUTPUT CHARACTERISTICS
Vout
Output Voltage Range
VOSC
Short Circuit Current
Full Scale at VDD=1.2
(Note 3)
0
4
AC ELECTRICAL CHARACTERISTICS
(Specification: VDD=1.2V, REFIN=1.15v,Temp=25°C, unless otherwise specified)
Symbol
Parameter
SR
Slew Rate
Ts
Settling Time
Fs
Conversion Speed
Td
Analog output Delay
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Rev A0.1
Test Conditions
Min
Typ
1.5
(Note 5)
(Note 4)
Max
Unit
2
V/µ
sµs
200
ksps
150
ns
Linearity is defined from code 127 to 3970 (ICM7722)
Guaranteed by design; not tested in production
See Applications Information
Output delay measured from the 50% point of the rising edge of input data to the full scale transition
Settling time measured from the 50% point of full scale transition to the output remaining within 1/2LSB.
ICmic reserves the right to change specifications without prior notice
3
ICM7722
TIMING CHARACTERISTICS
(VDD = 0.9V to 1.32v, all specifications TMIN to TMAX unless otherwise noted)
Symbol
Parameter
Test Conditions
Min
Typ
Max
Unit
SCK Cycle Time
Data Setup Time
(Note 2)
30
ns
t2
(Note 2)
10
ns
t3
Data Hold Time
(Note 2)
10
ns
t4
SCK Falling edge to CS Rising Edge
(Note 2)
0
ns
t5
CS Falling Edge to SCK Rising Edge
(Note 2)
10
ns
t6
CS Pulse Width
(Note 2)
20
ns
t1
TIMING DIAGRAM
Clk
50%
Td
Vout
50%
0000..0000
1111..1111
Data
0.5LSB
Vout
Ts
Rev A0.1
ICmic reserves the right to change specifications without prior notice
4
ICM7722
SERIAL INTERFACE TIMING AND OPERATION DIAGRAM
t5
t1
t4
t6
CS
SCK
SDI
C3
t2
C2
C1
D0
t3
MSB
LSB
Figure 1. Serial Interface Timing Diagram
CS
(UPDATE
OUTPUT)
(ENABLE
SCK)
SCK
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
SDI
C3
C2
C1
C0
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
MSB
D0
LSB
Figure 2. Serial Interface Operation Diagram
CONTENTS OF INPUT SHIFT REGISTER
DEVICE
CONTROL WORD
DATA WORD
MSB
ICM7722
C3
LSB
C2
C1
C0
D11 D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
Figure 3. Contents of Input Shift Register
Rev A0.1
ICmic reserves the right to change specifications without prior notice
5
ICM7722
FUNCTION
0
DATA
(D11-D0)
Data
A
Input Register transparent, data shifted to DAC register directly, VOA updated
0
0
0
1
0
1
Data
Data
Data
B
A
B
Input Register transparent, data shifted to DAC register directly, VOB updated
Data Shifted to Input Register, VOA unchanged
Data Shifted to Input Register, VOB unchanged
0
0
0
Data
A
Data Shifted from Input Register to DAC register, VOA updated
1
1
0
1
0
0
1
0
Data
Data
B
All
Data Shifted from Input Register to DAC register, VOB updated
Input Registers transparent, data shifted to DAC register directly, All VOUT updated
1
1
1
1
0
1
1
0
Data
Data
All
All
Data Shifted to Input Registers, All VOUT unchanged
Data Shifted from Input Registers to DAC registers, All VOUT updated
1
1
1
1
Data
All
Power Down Mode
C3
C2
C1
C0
0
0
0
0
0
0
0
1
1
1
DAC
FUNCTION
Table 1. Serial Interface Input Word
DETAILED DESCRIPTION
Serial Interface and Input Logic
The ICM7722 is a 12-bit voltage output Dual
DAC. This device has a 16-bit input shift
register and the DAC has a double buffered
digital input. This DAC has a guaranteed
monotonic behavior and the operating supply
range is from 0.9v to 1.32v.
Reference Input
The reference input accepts positive DC and AC
signals. The voltage at REFIN sets the full-scale
output voltage of both the DACs. To determine
the output voltage for any code, use the
following equation.
VOUT = VREF x (D / (2n))
Where D is the numeric value of DAC’s decimal
input code, VREF is the reference voltage and n
is number of bits, i.e. 12 for ICM7722.
Output Buffer Amplifier
Dual DAC has two amplifiers with a wide
output voltage swing. The actual swing of the
output amplifier will be limited by offset error
and gain error. See the Applications Information
Section for a more detailed discussion.
This Dual DAC uses a standard 3-wire
connection compatible with SPI/QSP and Micro
wire interfaces. Data is always loaded in 16bit words which consist of 4 control bits
(MSBs) followed by 12 bits (see Figure 3).
Serial Data Input
SDI (Serial Data Input) pin is the data input pin
for all the DACs. Data is clocked in on the
falling edge of SCK which has a Schmitt trigger
internally to allow for noise immunity on the
SCK pin. This specially eases the use for optocoupled interfaces.
The Chip Select pin which is the 3rd pin of 8
Lead TSSOP package is active low. This pin
frames the input data for synchronous loading
and must be low when data is being clocked into
the part. There is an onboard counter on the
clock input and after the 16th clock pulse
the data is automatically transferred to a 16-bit
input latch and the 4 bit
control
word
(C3~C0)
is
then
decoded and
the
appropriate command is performed depending
on the control word (see Table 1). Chip Select
pin must be pulled high (level-triggered) and
back low for the next data word to be loaded in.
This pin also disables the SCK pin internally
when pulled high.
The output amplifier can drive a load of 2.0 K Ω
to VDD or GND in parallel with a 500 pF load
capacitance.
The output amplifier has a full-scale typical
settling time of 2 µs and it dissipates about 500
µA with a 1.2V supply voltage.
Rev A0.1
ICmic reserves the right to change specifications without prior notice
6
ICM7722
APPLICATIONS INFORMATION
Power Supply Bypassing and Layout
Considerations
As in any precision circuit, careful consideration
has to be given to layout of the supply and
ground. The return path from the GND to the
supply ground should be short with low
impedance. Using a ground plane would be
ideal. The supply should have some bypassing
on it. A 10 µF tantalum capacitor in parallel
with a 0.1 µF ceramic with a low ESR can be
used. Ideally these would be placed as close as
possible to the device. Avoid crossing digital
and analog signals, specially the reference, or
running them close to each other.
Output Swing Limitations
The ideal rail-to-rail DAC would swing from
GND to VDD. However, offset and gain error
limit this ability. Figure 4 illustrates how a
negative offset error will affect the output. The
output will limit close to ground since this is
single supply part, resulting in a dead-band
area. As a larger input is loaded into the DAC
the output will eventually rise above ground.
This is why the linearity is specified for a
starting code greater than zero.
Figure 5 illustrates how a gain error or positive
offset error will affect the output when it is close
to VDD. A positive gain error or positive offset
will cause the output to be limited to the positive
supply voltage resulting in a dead-band of codes
close to full-scale.
Rev A0.1
VDD
DEADBAND
NEGATIVE
OFFSET
Figure 4. Effect of Negative Offset
OFFSET
AND GAIN
ERROR
VDD
DEAD BAND
POSITIVE
OFFSET
Figure 5. Effect of Gain Error and Positive Offset
ICmic reserves the right to change specifications without prior notice
7
ICM7722
PACKAGE INFORMATION
8 Lead TSSOP
Rev A0.1
ICmic reserves the right to change specifications without prior notice
8
ICM7722
PACKAGE INFORMATION
ICM77x2 P G
Device
1 - ICM7722
G = RoHS Compliant Lead-Free package.
Blank = Standard package. Non lead-free.
Package
T = 8-Lead TSSOP
Rev A0.1
ICmic reserves the right to change specifications without prior notice
9