LTC2449CUHF#PBF Linear Technology, LTC2449CUHF#PBF Datasheet - Page 24

• Manufacturer Part Number: LTC2449CUHF#PBF
• Description: IC ADC 24BIT 38-QFN
• Manufacturer: Linear Technology

Specifications of LTC2449CUHF#PBF

• Number Of Bits: 24
• Sampling Rate (per Second): 8k
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 40mW
• Voltage Supply Source: Single Supply
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 38-WFQFN, Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIO S I FOR ATIO
LTC2444/LTC2445/
LTC2448/LTC2449
Reduced Power Operation
In addition to adjusting the speed/resolution of the
LTC2444/LTC2445/LTC2448/LTC2449, the speed/reso-
lution/power dissipation may also be adjusted using the
automatic sleep mode. During the conversion cycle, the
LTC2444/LTC2445/LTC2448/LTC2449 draw 8mA supply
current independent of the programmed speed. Once the
conversion cycle is completed, the device automatically
enters a low power sleep state drawing 8µA. The device
remains in this state as long as CS is HIGH and data is not
shifted out. By adjusting the duration of the sleep state
(hold CS HIGH longer) and the duration of the conversion
cycle (programming OSR) the DC power dissipation can
be reduced, see Figure 14.
24
CONVERTER
CURRENT
SUPPLY
STATE
CS
SLEEP
8µA
U
U
DATA
OUT
V
V
I
V
V
I
W
REF
REF
I
I
REF
REF
IN
IN
IN
IN
+
+
–
–
+
+
–
–
8mA
Figure 15. LTC2444/LTC2448 Input Structure
CONVERT
V
V
Figure 14. Reduced Power Timing Mode
CC
CC
V
V
I
I
I
I
LEAK
LEAK
LEAK
LEAK
CC
CC
U
I
I
LEAK
LEAK
I
I
LEAK
LEAK
MUX
MUX
R
R
R
R
SW
SW
SW
SW
500Ω
500Ω
500Ω
500Ω
SWITCHING FREQUENCY
f
f
(TYP)
(TYP)
(TYP)
(TYP)
SW
SW
Average Input Current
The LTC2444/LTC2448 switch the input and reference to
a 2pF capacitor at a frequency of 1.8MHz. A simplified
equivalent circuit is shown in Figure 15. The sample
capacitor for the LTC2445/LTC2449 is 4pF, and its aver-
age input current is externally buffered from the input
source.
The average input and reference currents can be ex-
pressed in terms of the equivalent input resistance of the
sample capacitor, where: Req = 1/(f
When using the internal oscillator, f
equivalent resistance is approximately 110kΩ.
= 1.8MHz INTERNAL OSCILLATOR
= f
SLEEP
EOSC
8µA
/5 EXTERNAL OSCILLATOR
2440 F16
C
5pF
(TYP)
(C
SAMPLE CAP
+ PARASITICS)
EQ
EQ
= 2pF
DATA
OUT
8mA
CONVERT
SW
SW
is 1.8MHz and the
• Ceq)
8µA
SLEEP
2440 F15
2444589fb