msm6577 Oki Optical Components, msm6577 Datasheet - Page 18

• Manufacturer Part Number: msm6577
• Description: Operatable 0.9v Built-in Driver 4-bit Microcontroller
• Manufacturer: Oki Optical Components

(About–1.3 V)
¡ Semiconductor
NOTES ON USE
Power Supply for 0.9 V Microcontroller Series: Backup Flag and Constant-Voltage Circuit
The 0.9 V microcontroller series have a 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
of 1.5 V or 3.0 V can be selected.
The output (V
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
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
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 to 4 show
the internal status depending on the backup flag settings for the battery, as well as status
features.
*
V
(0 V)
V
(–1.5 V)
V
(–3.0 V)
V
(–4.5 V)
V
DD
SS1
SS2
SS3
EE
EE
) is equal to the input. The 0.9 V microcontroller can be operated even if the internal
EE
LCD driver*
) of the constant-voltage circuit is set at approximately –1.3 V. This allows the
* The V
LCD driver.
converter
Voltage
SS3
pin is provided for the devices that contain an
Constant voltage circuit
Backup flag
(BUF)
VR
Internal
logic
XTB
XT
MSM6577-xx
XTAL
18/22
EE
)