Datasheet

LT6656
13
6656fa
0.1µF 10µF
LT6656-2.5
3V ≤ V
IN
≤ 18V
6656 TA02
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
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 microcontrollers on board ADC.
Figure 12. Microcontroller Reference and Regulator
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 13 shows the LTC2480, a
low power delta sigma ADC. When the ADC is disabled its
quiescent current (I
Q
) is roughly 1µA, during conversion the
I
Q
jumps up to 160µA. In reality, the power consumption
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 13
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 average current drawn by the ADC
during a 1 second interval would only be 26.4µA. When
taking into consideration the current drawn by the refer-
ence, 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.
Figure 13. Low Power ADC Reference
0.1µF
5.1V ≤ V
IN
≤ 18V
4.7µF
6656 TA05
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