P89C738ABB View Datasheet(PDF) - Philips Electronics
Part Name
Description
MFG CO.
'P89C738ABB' PDF : 64 Pages View PDF
Philips Semiconductors
8-bit Flash microcontrollers
Product specification
P89C738; P89C739
14 OSCILLATOR CIRCUIT
The oscillator circuit of the P89C738 is a single-stage
inverting amplifier in a Pierce oscillator configuration.
The circuitry between the XTAL 1 and XTAL 2 is basically
an inverter biased to the transfer point. Either a crystal or
ceramic resonator can be used as the feedback element to
complete the oscillator circuitry (see Fig.19).
Both are operated in parallel resonance. XTAL 1 is the
high gain amplifier input, and XTAL 2 is the output (see
Fig.18).
To drive the P89C738 externally, XTAL 1 is driven from an
external source and XTAL 2 left open-circuit (see Fig.20).
handbook, full pagewidth
to internal
timing circuits
XTAL1
D1
400 Ω
Q1
D2
VDD
Q2
R1
Q3
XTAL2
PO
Q4
VSS
MGK196
Fig.18 P89C738/P89C739 oscillator internal circuit.
handbook, halfpage
C1
20 pF
C2
20 pF
XTAL1
MBK775
XTAL2
Fig.19 P89C738/P89C739 oscillator circuit
with crystal/ceramic resonator.
handbook, halfpage
NC
external
oscillator
signal
CMOS gate
XTAL2
XTAL1
VSS
MGK197
Fig.20 Driving the P89C738/P89C739 from an
external source.
1998 Apr 07
31
Share Link: 
