LTC2404/LTC2408
4-/8-Channel 24-Bit
µPower
No Latency
∆Σ
TM
ADCs
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
Pin Compatible 4-/8-Channel 24-Bit ADCs
Single Conversion Digital Filter Settling Time
Simplifies Multiplexing
4ppm INL, No Missing Codes
4ppm Full-Scale Error
0.5ppm Offset
0.3ppm Noise
Internal Oscillator—No External Components
Required
110dB Min, 50Hz/60Hz Notch Filter
Reference Input Voltage: 0.1V to V
CC
Live Zero—Extended Input Range Accommodates
12.5% Overrange and Underrange
Single Supply 2.7V to 5.5V Operation
Low Supply Current (200µA) and Auto Shutdown
The LTC
®
2404/LTC2408 are 4-/8-channel 2.7V to 5.5V
micropower 24-bit A/D converters with an integrated
oscillator, 4ppm INL and 0.3ppm RMS noise. They use
delta-sigma technology and provide single cycle digital
filter settling time (no latency delay) for multiplexed
applications. The first conversion after the channel is
changed is always valid. Through a single pin the LTC2404/
LTC2408 can be configured for better than 110dB rejec-
tion at 50Hz or 60Hz
±2%,
or can be driven by an external
oscillator for a user defined rejection frequency in the
range 1Hz to 120Hz. The internal oscillator requires no
external frequency setting components.
The converters accept any external reference voltage from
0.1V to V
CC
. With their extended input conversion range of
–12.5% V
REF
to 112.5% V
REF
the LTC2404/LTC2408
smoothly resolve the offset and overrange problems of
preceding sensors or signal conditioning circuits.
The LTC2404/LTC2408 communicate through a flexible
4-wire digital interface which is compatible with SPI and
MICROWIRE
TM
protocols.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No Latency
∆Σ
is a trademark of Linear Technology Corporation.
MICROWIRE is a trademark of National Semiconductor Corporation.
APPLICATIO S
s
s
s
s
s
s
s
s
Weight Scales
Direct Temperature Measurement
Gas Analyzers
Strain Gauge Transducers
Instrumentation
Data Acquisition
Industrial Process Control
6-Digit DVMs
TYPICAL APPLICATIO
7
MUXOUT
9 CH0
10 CH1
11 CH2
ANALOG
INPUTS
–0.12V
REF
TO
1.12V
REF
12 CH3
4-/8-CHANNEL
13 CH4*
MUX
14 CH5*
15 CH6*
17 CH7*
0.1V TO V
CC
4
ADCIN
3
2, 8
V
REF
V
CC
CSADC
CSMUX
24-BIT
∆Σ
ADC
SCK
CLK
D
IN
SDO
LTC2404/LTC2408
GND
1, 5, 6, 16, 18, 22, 27, 28
*THESE PINS ARE NO CONNECTS ON THE LTC2404
F
O
2404/08 TA01
2.7V TO 5.5V
1µF
SERIAL DATA LINK
MICROWIRE AND
SPI COMPATABLE
LINEARITY ERROR (ppm)
23
20
19
25
21
24
MPU
V
CC
26
= INTERNAL OSC/50Hz REJECTION
= EXTERNAL CLOCK SOURCE
= INTERNAL OSC/60Hz REJECTION
U
Total Unadjusted Error vs Output Code
10
8
6
4
2
0
–2
–4
–6
–8
–10
0
8,338,608
OUTPUT CODE (DECIMAL)
16,777,215
2404/08 TA02
U
U
V
DD
= 5V
V
REF
= 5V
T
A
= 25°C
F
O
= LOW
1
LTC2404/LTC2408
ABSOLUTE
MAXIMUM
RATINGS
(Notes 1, 2)
Supply Voltage (V
CC
) to GND .......................– 0.3V to 7V
Analog Input Voltage to GND ....... – 0.3V to (V
CC
+ 0.3V)
Reference Input Voltage to GND .. – 0.3V to (V
CC
+ 0.3V)
Digital Input Voltage to GND ........ – 0.3V to (V
CC
+ 0.3V)
Digital Output Voltage to GND ..... – 0.3V to (V
CC
+ 0.3V)
PACKAGE/ORDER INFORMATION
TOP VIEW
GND
V
CC
V
REF
ADCIN
GND
GND
MUXOUT
V
CC
CH0
1
2
3
4
5
6
7
8
9
28 GND
27 GND
26 F
O
25 SCK
24 SDO
23 CSADC
22 GND
21 D
IN
20 CSMUX
19 CLK
18 GND
17 NC
16 GND
15 NC
ORDER
PART NUMBER
LTC2404CG
LTC2404IG
CH1 10
CH2 11
CH3 12
NC 13
NC 14
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 130°C/W
Consult factory for Military grade parts.
CONVERTER CHARACTERISTICS
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
PARAMETER
Resolution (No Missing Codes)
Integral Nonlinearity
Offset Error
Offset Error Drift
Full-Scale Error
Full-Scale Error Drift
Total Unadjusted Error
Output Noise
Normal Mode Rejection 60Hz
±2%
CONDITIONS
0.1V
≤
V
REF
≤
V
CC
, (Note 5)
V
REF
= 2.5V (Note 6)
V
REF
= 5V (Note 6)
2.5V
≤
V
REF
≤
V
CC
2.5V
≤
V
REF
≤
V
CC
2.5V
≤
V
REF
≤
V
CC
2.5V
≤
V
REF
≤
V
CC
V
REF
= 2.5V
V
REF
= 5V
V
IN
= 0V (Note 13)
(Note 7)
q
q
q
q
q
q
2
U
U
W
W W
U
W
Operating Temperature Range
LTC2404C/LTC2408C .............................. 0°C to 70°C
LTC2404I/LTC2408I ........................... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
GND
V
CC
V
REF
ADCIN
GND
GND
MUXOUT
V
CC
CH0
1
2
3
4
5
6
7
8
9
28 GND
27 GND
26 F
O
25 SCK
24 SDO
23 CSADC
22 GND
21 D
IN
20 CSMUX
19 CLK
18 GND
17 CH7
16 GND
15 CH6
ORDER
PART NUMBER
LTC2408CG
LTC2408IG
CH1 10
CH2 11
CH3 12
CH4 13
CH5 14
G PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 130°C/W
U
MIN
24
TYP
2
4
0.5
0.01
4
0.02
5
10
1.5
MAX
10
15
2
10
UNITS
Bits
ppm of V
REF
ppm of V
REF
ppm of V
REF
ppm of V
REF
/°C
ppm of V
REF
ppm of V
REF
/°C
ppm of V
REF
ppm of V
REF
µV
RMS
dB
110
130
LTC2404/LTC2408
CONVERTER CHARACTERISTICS
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Notes 3, 4)
PARAMETER
Normal Mode Rejection 50Hz
±2%
Power Supply Rejection DC
Power Supply Rejection 60Hz
±2%
Power Supply Rejection 50Hz
±2%
CONDITIONS
(Note 8)
V
REF
= 2.5V, V
IN
= 0V
V
REF
= 2.5V, V
IN
= 0V, (Note 7)
V
REF
= 2.5V, V
IN
= 0V, (Note 8)
q
A ALOG I PUT A D REFERE CE
SYMBOL
V
IN
V
REF
C
S(IN)
C
S(REF)
I
IN(LEAK)
I
REF(LEAK)
I
IN(MUX)
R
ON
PARAMETER
Input Voltage Range
Reference Voltage Range
Input Sampling Capacitance
Reference Sampling Capacitance
Input Leakage Current
Reference Leakage Current
On Channel Leakage Current
MUX On-Resistance
MUX
∆R
ON
vs Temperature
∆R
ON
vs V
S
(Note 15)
I
S(OFF)
I
D(OFF)
t
OPEN
t
ON
t
OFF
QIRR
QINJ
C
S(OFF)
C
D(OFF)
MUX Off Input Leakage
MUX Off Output Leakage
MUX Break-Before-Make Interval
Enable Turn-On Time
Enable Turn-Off Time
MUX Off Isolation
Charge Injection
Input Off Capacitance (MUX)
Output Off Capacitance (MUX)
CS = V
CC
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
(Note 14)
q
q
V
REF
= 2.5V, CS = V
CC
V
S
= 2.5V (Note 15)
I
OUT
= 1mA, V
CC
= 2.7V
I
OUT
= 1mA, V
CC
= 5V
Channel Off, V
S
= 2.5V
Channel Off, V
D
= 2.5V
V
S
= 1.5V, R
L
= 3.4k, C
L
= 15pF
V
S
= 1.5V, R
L
= 3.4k, C
L
= 15pF
V
IN
= 2V
P-P
, R
L
= 1k, f = 100kHz
R
S
= 0Ω, C
L
= 1000pF, V
S
= 1V
U
U
U
U
MIN
110
TYP
130
100
110
110
MAX
UNITS
dB
dB
dB
dB
U
MIN
– 0.125 • V
REF
0.1
TYP
MAX
1.125 • V
REF
V
CC
UNITS
V
V
pF
pF
10
15
q
q
q
q
q
–10
– 12
1
1
250
120
0.5
20
10
12
±20
300
250
nA
nA
nA
Ω
Ω
%/°C
%
q
q
±20
±20
290
490
190
70
±1
10
10
nA
nA
ns
ns
ns
dB
pC
pF
pF
3
LTC2404/LTC2408
DIGITAL I PUTS A D DIGITAL OUTPUTS
SYMBOL
V
IH
V
IL
V
IH
V
IL
I
IN
I
IN
C
IN
C
IN
V
OH
V
OL
V
OH
V
OL
I
OZ
V
IN
H
MUX
V
IN
L
MUX
PARAMETER
High Level Input Voltage
CS, F
O
Low Level Input Voltage
CS, F
O
High Level Input Voltage
SCK
Low Level Input Voltage
SCK
Digital Input Current
CS, F
O
Digital Input Current
SCK
Digital Input Capacitance
CS, F
O
Digital Input Capacitance
SCK
High Level Output Voltage
SDO
Low Level Output Voltage
SDO
High Level Output Voltage
SCK
Low Level Output Voltage
SCK
High-Z Output Leakage
SDO
MUX High Level Input Voltage
MUX Low Level Input Voltage
V
+
= 3V
V
+
= 2.4V
(Note 9)
I
O
= – 800µA
I
O
= 1.6mA
I
O
= – 800µA (Note 10)
I
O
= 1.6mA (Note 10)
q
q
q
q
q
q
q
The
q
denotes specifications which apply over the full
operating temperature range, otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
2.7V
≤
V
CC
≤
5.5V
2.7V
≤
V
CC
≤
3.3V
4.5V
≤
V
CC
≤
5.5V
2.7V
≤
V
CC
≤
5.5V
2.7V
≤
V
CC
≤
5.5V (Note 9)
2.7V
≤
V
CC
≤
3.3V (Note 9)
4.5V
≤
V
CC
≤
5.5V (Note 9)
2.7V
≤
V
CC
≤
5.5V (Note 9)
0V
≤
V
IN
≤
V
CC
0V
≤
V
IN
≤
V
CC
(Note 9)
q
q
q
q
q
q
POWER REQUIRE E TS
SYMBOL
V
CC
I
CC
PARAMETER
Supply Voltage
Supply Current
Conversion Mode
Sleep Mode
Multiplexer Supply Current
The
q
denotes specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C. (Note 3)
CONDITIONS
q
I
CC(MUX)
4
U W
U
U
MIN
2.5
2.0
TYP
MAX
UNITS
V
V
0.8
0.6
2.5
2.0
0.8
0.6
–10
–10
10
10
V
CC
– 0.5V
0.4V
V
CC
– 0.5V
0.4V
–10
2
0.8
10
10
10
V
V
V
V
V
V
µA
µA
pF
pF
V
V
V
V
µA
V
V
MIN
2.7
TYP
MAX
5.5
UNITS
V
µA
µA
µA
CS = 0V (Note 12)
CS = V
CC
(Note 12)
All Logic Inputs Tied Together
V
IN
= 0V or 5V
q
q
q
200
20
15
300
30
40
LTC2404/LTC2408
TI I G CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range,
otherwise specifications are at T
A
= 25°C. (Note 3)
PARAMETER
External Oscillator Frequency Range
External Oscillator High Period
External Oscillator Low Period
Conversion Time
F
O
= 0V
F
O
= V
CC
External Oscillator (Note 11)
Internal Oscillator (Note 10)
External Oscillator (Notes 10, 11)
(Note 10)
(Note 9)
(Note 9)
(Note 9)
Internal Oscillator (Notes 10, 12)
External Oscillator (Notes 10, 11)
(Note 9)
q
q
q
q
q
q
q
q
SYMBOL
f
EOSC
t
HEO
t
LEO
t
CONV
f
ISCK
D
ISCK
f
ESCK
t
LESCK
t
HESCK
t
DOUT_ISCK
t
DOUT_ESCK
t
1
t
2
t
3
t
4
t
KQMAX
t
KQMIN
t
5
t
6
Note 1:
Absolute Maximum Ratings are those values beyond which the
life of the device may be impaired.
Note 2:
All voltage values are with respect to GND.
Note 3:
V
CC
= 2.7 to 5.5V unless otherwise specified, source input
is 0Ω.
Note 4:
Internal Conversion Clock source with the F
O
pin tied
to GND or to V
CC
or to external conversion clock source with
f
EOSC
= 153600Hz unless otherwise specified.
Note 5:
Guaranteed by design, not subject to test.
Note 6:
Integral nonlinearity is defined as the deviation of a code from
a straight line passing through the actual endpoints of the transfer
curve. The deviation is measured from the center of the quantization
band.
Note 7:
F
O
= 0V (internal oscillator) or f
EOSC
= 153600Hz
±2%
(external oscillator).
Note 8:
F
O
= V
CC
(internal oscillator) or f
EOSC
= 128000Hz
±2%
(external oscillator).
Note 9:
The converter is in external SCK mode of operation such that
the SCK pin is used as digital input. The frequency of the clock signal
driving SCK during the data output is f
ESCK
and is expressed in kHz.
UW
CONDITIONS
q
q
q
q
q
q
MIN
2.56
0.5
0.5
TYP
MAX
307.2
390
390
UNITS
kHz
µs
µs
ms
ms
ms
kHz
kHz
130.66
133.33
136
156.80
160
163.20
20480/f
EOSC
(in kHz)
19.2
f
EOSC
/8
45
250
250
1.64
1.67
1.70
256/f
EOSC
(in kHz)
32/f
ESCK
(in kHz)
0
0
0
50
200
15
50
50
150
150
150
55
2000
Internal SCK Frequency
Internal SCK Duty Cycle
External SCK Frequency Range
External SCK Low Period
External SCK High Period
Internal SCK 32-Bit Data Output Time
External SCK 32-Bit Data Output Time
CS
↓
to SDO Low Z
CS
↑
to SDO High Z
CS
↓
to SCK
↓
CS
↓
to SCK
↑
SCK
↓
to SDO Valid
SDO Hold After SCK
↓
SCK Set-Up Before CS
↓
SCK Hold After CS
↓
%
kHz
ns
ns
ms
ms
ms
ns
ns
ns
ns
ns
ns
ns
ns
(Note 10)
(Note 9)
(Note 5)
q
q
q
q
q
q
Note 10:
The converter is in internal SCK mode of operation such that
the SCK pin is used as digital output. In this mode of operation the
SCK pin has a total equivalent load capacitance C
LOAD
= 20pF.
Note 11:
The external oscillator is connected to the F
O
pin. The external
oscillator frequency, f
EOSC
, is expressed in kHz.
Note 12:
The converter uses the internal oscillator.
F
O
= 0V or F
O
= V
CC
.
Note 13:
The output noise includes the contribution of the internal
calibration operations.
Note 14:
For reference voltage values V
REF
> 2.5V the extended input
of – 0.125 • V
REF
to 1.125 • V
REF
is limited by the absolute maximum
rating of the Analog Input Voltage pin (Pin 3). For 2.5V < V
REF
≤
0.267V + 0.89 • V
CC
the input voltage range is – 0.3V to 1.125 • V
REF
.
For 0.267V + 0.89 • V
CC
< V
REF
≤
V
CC
the input voltage range is – 0.3V
to V
CC
+ 0.3V.
Note 15:
V
S
is the voltage applied to a channel input. V
D
is the voltage
applied to the MUX output.
5
