Philips Semiconductors
Product specification
4-digit LED-driver with I2C-Bus interface
SAA1064
SDA, SCL
The SDA and SCL I/O meet the I2C-Bus specification. For protection against positive voltage pulses on these inputs
voltage regulator diodes are connected to VEE. This means that normal line voltage should not exceed 5,5 volt. Data will
be latched on the positive-going edge of the acknowledge related clock pulse.
Power-on reset
The power-on reset signal is generated internally and sets all bits to zero, resulting in a completely blanked display. Only
the POWER RESET flag is set.
External Control (CEXT
)
With a capacitor connected to pin 2 the multiplex frequency can be set (see Fig.5). When static this pin can be connected
to VEE or VCC or left floating since the oscillator will be switched off.
Segment outputs
The segment outputs P1 to P16 are controllable current-sink sources. They are switched on by the corresponding data
bits and their current is adjusted by control bits C4, C5 and C6.
Multiplex outputs
The multiplex outputs MX1 and MX2 are switched alternately in dynamic mode with a frequency derived from the
clock-oscillator. In static mode MX1 is switched on. The outputs consist of an emitter-follower, which can be used to drive
the common anodes of two displays directly provided that the total power dissipation of the circuit is not exceeded. If this
occurs external transistors should be connected to pins 11 and 14 as shown in Fig.5.
February 1991
7
NXP [ NXP ]
