Z86L972 Datasheet, PDF (35/91 Pages) Zilog, Inc. – Low-Voltage Microcontrollers

Z86L972/Z86L973/Z86L974
Low-Voltage Microcontrollers
28
Controlled Current Output
P43 is an open-drain pin that can be configured as output or Tristate High Imped-
ance. To function properly, Bit 3 of P4M must be set to zero to configure the pin as
an open-drain output. After reset, P43 defaults to Tristate High Impedance. The
data at Port 4 must be initialized as it is undefined at power-on reset.
The current output is a controlled current source that is controlled by the output of
the value of P43 (see Table 9). P43 cannot be configured as input, and if P43 is
read, P43 always returns the state of the output value (1 for no sink and 0 for
sink).
Before going into STOP mode, P43 must be set to 1 to reduce STOP mode cur-
rent.n
Table 9. Current Sink Pad P43 Specifications (Preliminary)
Parameter
Rise time
Fall time
V_outmin
Comparator response
Regulated current
Internal resistance
Min
80 mA
Max
0.4 µ
0.02 µ
0.54 V
0.2 µ
120 mA
80 Ω
Conditions
LED load
LED load
@27C
The pad driver can function in two modes:
• controlled current output, when the voltage on the pad is over a minimum
value
V_pad > V_outmin
• resistive pull down when the driver cannot regulate the current; in this mode,
the gate of the NMOS pull down is raised to the power rail.
The I-V characteristics of the pad are presented in Figure 14.
PS010504-1002
PRELIMINARY