Datasheet

LT6656
17
6656fc
For more information www.linear.com/LT6656
TYPICAL APPLICATIONS
Regulator Reference
The robust input and output of the LT6656 along with its
high output current make it an excellent precision low
power regulator as well as a reference. The LT6656 would
be a good match with a small, low power microcontroller.
Using the LT6656 as a regulator reduces power consump
-
tion, decreases solution size and increases the accuracy
of the microcontroller’s on board ADC.
Low Power ADC Reference
Low power ADCs draw only a few µAs during their idle
period and well over 100µA during conversions. Despite
these surges of current, the ADC in reality can have very
low power consumption. Figure 17 shows the LTC2480,
a low power delta sigma ADC. When the ADC is disabled
its quiescent current (I
Q
) is roughly 1µA, during conver-
sion the I
Q
jumps up to 160µA. In reality, the power con-
sumption is not only based on the I
Q
during conversion,
but the real power consumption of the ADC is set by the
conversion time and the sample rate. The LTC2480 shown
in Figure 17 has a conversion time of 160ms which sets
the maximum sample rate of 6 samples per second. The
maximum sample rate also sets the maximum current
consumption to 160µA, but at slower sample rates the
ADC will have significantly lower average current draw.
If the ADC is sampled at 1 sample per second the aver
-
age current drawn by the ADC during a 1 second interval
would only be 26.4µA. When taking into consideration the
current drawn by the reference, the total current draw is
only 27.4µA. This system is greatly simplified because
the precision reference does not need to be cycled on and
off to save power. Furthermore, leaving the reference on
continuously eliminates concern for turn-on settling time.
0.1µF 10µF
LT6656-2.5
3V ≤ V
IN
≤ 18V
6656 F16
PB0/AIN0/A
REF
/MOSI
MCU
5
PB1/INT0/A
IN1
/MISO/OC1A
6
PB2/ADC1/SCK/T0/INT0
7
PB3/ADC2
2
PB4/ADC3
3
PB5/RESET/ADC0
1
V
CC
/V
REF
GND
OUTIN
0.1µF
5.1V ≤ V
IN
≤ 18V
4.7µF
6656 F17
DIFFERENTIAL INPUT
±V
REF
• 0.5 (±2.5V)
AT 1sps, I
Q
= 27.4µA
LT6656-5
IN OUT
SDOIN
–
CS
SCK
IN
+
LTC2480
V
CC
REF
Figure 16. Microcontroller Reference and Regulator
Figure 17. Low Power ADC Reference