BU97950FUV Datasheet, PDF (17/25 Pages) Rohm – Standard LCD Segment Drivers

BU97950FUV MAX 280 segments (SEG35×COM8)
●Note on the number of LSIs being connected to the same bus.
Do not access the other device without power supply (VDD) to the BU97950.
Controller
BU97950
Device1
Figure 15. Example of BUS connection
To control the slope of the falling edge, a capacitor is connected between gate and drain of a NMOS transistor (Refer to
Figure16).
The gate is in a high-impedance state if the power supply (VDD) is not supplied.
In this condition, the gate voltage is pulled up by the current flow through the capacitance as a result of the SDA signal's
transition from LOW to HIGH.
The NMOS transistor turns on and draws some current (Ids) from the SDA port if the gate voltage (Vg) is higher than the
threshold voltage (Vth).
An external resistor (R) is connected between the power line and SDA line to keep the SDA line as logic HIGH.
But the line cannot be kept as logic HGH if the voltage drop (R*Ids) is large.
Access the other LSIs with power supply to BU9792x to control the gate voltage as logic level of 1 or 0 if the number of LSIs are
connected to the same bus.
VDD
Z=1/jω C
SDA
internal circuit
Vg
Figure 16. SDA output cell structure
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