BATTERY POWERED LOW-POWER PIR SENSOR INTERFACE
• Power derived from 3.0V Lithium battery
• VDD operating range 2.3V to 3.6V
• 25μA maximum quiescent current (LS6525)
• 30μA maximum quiescent current (LS6526)
• Direct interface with PIR sensor
• Analog signal and digital interrupt signal outputs for interfacing
with a MCU
• 2.175V regulated output
• Low battery indicator output (LS6526)
• LS6525 (DIP), LS6525-S (SOIC)
LS6526 (DIP), LS6526-S (SOIC)
The low operating voltage and low current drain make the LS65 25 /
LS6526 ideal for microcontroller based portable applications such as
battery operate d motion detectors and photographic equipment,
automatic doors, intrusion detecti on, and anywhere electric outlets
are not available.
The LS6525 / LS6526 is a CMOS integrated circuit designe d fo r
detecting motion from a PIR sen sor and is micro controller interface
ready. It uses a 3.0V Li battery as a source of energy fo
operation. The detailed de scription of the functional b locks is as
follows (refer to Figure 2).
The input PIR p reamplifier, AMP1, has a nominal gain set at 29V/V
using internal resistors. An int ernal bias is u sed so that AMP1O
output has a q uiescent voltage of 1.1V. The output of the PIR
amplifier is AC coupled to a second amplifier (AMP2) which uses
external components to set the gain. This secon d stage is internally
biased and applied to a window comparator which has lower and
higher trip levels set with respe ct to that bias. External components
are used to set a typical gain of 22V/V. Amplifie d signals greater in
magnitude than the trip levels will cause an in terrupt signal to be
generated at the INT open drain output, pin 12. The INT output can
be pulled to a voltage higher than VDD (pin 13).
The output of the PIR amplifier i s also AC coupled to an additional
amplifier (MCU amplifier) which uses external components to set the
gain. An internal bias set the MCO output a t 0.5V and external
resistors set a typical ga in = 10V/V, the MCO o utput signal can be
applied to a microcontroller input for processing.
INPUT / OUTPUT DESCRIPTION
PIN1 – PYRO Input – Non-inverting input of PIR amplifier AC
coupled to source of PIR signal.
PIN2 – VREG Output – This output provides power to the PIR
Sensor circuit and for all the internal amplifier circuitry.
PIN3 – AMP1O Output – Output terminal of the PIR amplifier
PIN4 – MCP – 0.5V internal bias. (Internal use only. No external
PIN5 – MCN Input – Inverting input to the MCU amplifier.
PIN6 – MCO Output – Output of the MCU amplifier.