LTC1198-1ACS8 Linear Technology, LTC1198-1ACS8 Datasheet - Page 17

• Manufacturer Part Number: LTC1198-1ACS8
• Description: IC ADC 8BIT 750KHZ SAMPL 8-SOIC
• Manufacturer: Linear Technology

Specifications of LTC1198-1ACS8

• Number Of Bits: 8
• Sampling Rate (per Second): 750k
• Data Interface: Serial
• Number Of Converters: 1
• Power Dissipation (max): 50mW
• Voltage Supply Source: Single Supply
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS INFORMATION
REDUCING POWER CONSUMPTION
The LTC1196/LTC1198 can sample at up to a 1MHz rate,
drawing only 50mW from a 5V supply. Power consumption
can be reduced in two ways. Using a 3V supply lowers the
power consumption on both devices by a factor of fi ve,
to 10mW. The LTC1198 can reduce power even further
because it shuts down whenever it is not converting.
Figure 5 shows the supply current versus sample rate for
the LTC1196 and LTC1198 on 3V and 5V. To achieve such
a low power consumption, especially for the LTC1198,
several things must be taken into consideration.
Shutdown (LTC1198)
Figure 2 shows the operating sequence of the LTC1198.
The converter draws power when the CS pin is LOW and
powers itself down when that pin is HIGH. For lowest
power consumption in shutdown, the CS pin should be
driven with CMOS levels (0V to V
buffer of the converter will not draw current.
When the CS pin is HIGH (= supply voltage), the LTC1198
is in shutdown mode and draws only leakage current.
The status of the D
supply current during this time. There is no need to stop
Figure 5. Supply Current vs Sample Rate for LTC1196/LTC1198
Operating on 5V and 2.7V Supplies
0.001
0.01
0.1
10
1
100
LT1198 V
LT1196 V
LT1198 V
IN
1k
SAMPLE RATE (Hz)
and CLK input has no effect on the
CC
CC
CC
= 2.87V
= 5V
LT1198 V
= 5V
10k
CC
CC
100k
= 2.87V
) so that the CS input
1196/98 F05
1M
D
without drawing current.
Minimize CS LOW Time (LTC1198)
In systems that have signifi cant time between conver-
sions, lowest power drain will occur with the minimum CS
LOW time. Bringing CS LOW, transferring data as quickly
as possible, then bringing it back HIGH will result in the
lowest current drain. This minimizes the amount of time
the device draws power.
OPERATING ON OTHER THAN 5V SUPPLIES
The LTC1196/LTC1198 operate from single 2.7V to 6V
supplies. To operate the LTC1196/LTC1198 on other than
5V supplies, a few things must be kept in mind.
Input Logic Levels
The input logic levels of CS, CLK and D
meet TTL on 5V supply. When the supply voltage varies,
the input logic levels also change (see the Digital Input
Logic Threshold vs Supply Voltage curve in the Typical
Performance Characteristics section). For these two ADCs
to sample and convert correctly, the digital inputs have to
be in the logical LOW and HIGH relative to the operating
supply voltage. If achieving micropower consumption
is desirable on the LTC1198, the digital inputs must go
rail-to-rail between supply voltage and ground (see the
Reducing Power Consumption section).
Clock Frequency
The maximum recommended clock frequency is 14.4MHz
at 25°C for the LTC1196/LTC1198 running off a 5V supply.
With the supply voltage changing, the maximum clock
frequency for the devices also changes (see the Maximum
Clock Rate vs Supply Voltage curve in the Typical Perfor-
mance Characteristics section). If the supply is reduced,
the clock rate must also be reduced. At 3V, the devices
are specifi ed with a 5.4MHz clock at 25°C.
IN
and CLK with CS = HIGH; they can continue to run
LTC1196/LTC1198
IN
are made to
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