MSM6576 Datasheet, PDF (9/12 Pages) OKI electronic componets – Operatable at 0.9 V and 7-level Detector 4-Bit Microcontroller

¡ Semiconductor
MSM6576
NOTES ON USE
Power Supply for 0.9 V Microcontroller Series (Backup Flag and Constant-Voltage Circuit)
The 0.9 V microcontroller series has built-in constant-voltage circuit. The output of this
constant-voltage circuit powers the microcontroller's internal logic circuits. Setting a backup
flag (BUF) allows the input of the constant-voltage circuit to be switched to either the battery
or the output generated in the voltage converter, based on the battery voltage. A battery voltage
is 1.5 V.
V_DD
(0 V)
V_SS1
(–1.5 V)
V_SS2
(–3.0 V)
V_SS3*
(–4.5 V)
V_EE
(About–1.3 V)
LCD driver*
Voltage
converter
Backup flag
(BUF)
Internal
logic
XT
XTB
Constant-voltage circuit
VR
*The V_SS3 pin is provided for the devices that contain an
LCD driver.
XTAL
The output (V_EE) of the constant-voltage circuit is set at approximately –1.3 V. This allows the
current consumed by the internal logic to be limited, irrespective of the battery voltage.
However, if the input of the constant-voltage circuit is below this set value (about –1.3 V), the
output (V_EE) is equal to the input. The 0.9 V microcontroller can be operated even if the internal
voltage (output from the constant-voltage circuit) falls to 0.9 V. Setting the backup flag allows
a larger operating voltage margin despite changes in internal voltage due to noise. For example,
for the 1.5 V operation, setting the backup flag to "0" supplies twice the battery voltage to the
constant-voltage circuit. Thus, even if the battery voltage falls to 0.9 V, the output voltage (V_EE)
is maintained at –1.3 V, providing a larger margin of operating voltage of the internal logic
circuits because 1.8 V is applied to the input of the constant-voltage circuit. Figures 1 and 2 show
the internal status depending on the backup flag settings for the battery, as well as status
features.
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