
S1C6S2N7 TECHNICAL HARDWARE
EPSON
I-55
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (SVD Circuit and Heavy Load Protection Function)
4.9
Configuration of SVD
circuit and heavy
load protection
function
Supply Voltage Detection (SVD) Circuit and
Heavy Load Protection Function
The S1C6S2N7 Series has a built-in supply voltage detection
(SVD) circuit and a heavy load protection function. Figure
4.9.1 shows the configuration of the circuit.
SVD circuit
The SVD circuit monitors the conditions of the supply
voltage (battery voltage), and software can check whether the
supply voltage has dropped below the detecting voltage level
of the SVD circuit: 2.4 V for the S1C6S2N7/S1C6S2A7
(supply voltage is 3.0 V), or l.2 V for the S1C6S2L7/
S1C6S2B7 (1.5 V). Registers SVDON (SVD control on/off)
and SVDDT (SVD data) are used for the SVD circuit. The
software can turn SVD operation on and off. When SVD is
on, the IC draws a large current, so keep SVD off unless it is.
Since supply voltage detection is automatically performed by
the hardware every 2 Hz (0.5 sec) when the heavy load
protection function operates, do not permit the operation of
the SVD circuit by the software in order to minimize power
current consumption.
Heavy load protection function
Note that the heavy load protection function on the
S1C6S2L7/S1C6S2B7 are different from the S1C6S2N7/
S1C6S2A7.
(1) In case of S1C6S2L7/S1C6S2B7
The S1C6S2L7/S1C6S2B7 have the heavy load protec-
tion function for when the battery load becomes heavy
and the source voltage drops, such as when an external
buzzer sounds or an external lamp lights. The state
where the heavy load protection function is in effect is
called the heavy load protection mode. In this mode,
operation with a lower voltage than normal is possible.
The normal mode changes to the heavy load protection
mode in the following two cases:
When the software changes the mode to the heavy load
protection mode (HLMOD = 1)
When supply voltage drop (SVDDT = 1) in the SVD
circuit is detected, the mode will automatically shift to
the heavy load protection mode until the supply volt-
age is recovered (SVTDT = 0)