ST92T163 ST Microelectronics, ST92T163 Datasheet - Page 85

• Manufacturer Part Number: ST92T163
• Description: 8/16-BIT FULL SPEED USB MCU FOR COMPOSITE DEVICES WITH 16 ENDPOINTS
• Manufacturer: ST Microelectronics

5.5 OSCILLATOR CHARACTERISTICS
The oscillator circuit uses an inverting gate circuit
with tri-state output.
Notes: Owing to the Q factor required, Ceramic
Resonators may not provide a reliable oscillator
source .
OSCOUT must not be directly used to drive exter-
nal circuits.
When the oscillator is stopped, OSCOUT goes
high impedance.
In Halt mode, set by means of the HALT instruc-
tion, the parallel resistor, R, is disconnected and
the oscillator is disabled, forcing the internal clock,
CLOCK1, to a high level, and OSCOUT to a high
impedance state.
To exit the HALT condition and restart the oscilla-
tor, an external RESET pulse is required.
It should be noted that, if the Watchdog function is
enabled, a HALT instruction will not disable the os-
cillator. This to avoid stopping the Watchdog if a
HALT code is executed in error. When this occurs,
the CPU will be reset when the Watchdog times
out or when an external reset is applied.
Table 16. Oscillator Transconductance
Figure 42. Crystal Oscillator
Symbol
gm
4.0-5.5V
3.0-4.0V
Voltage
range
C
*Recommended for oscillator stability
L1
OSCIN
CRYSTAL CLOCK
0.77
Min
0.5
ST9
1M*
0.73
Typ
OSCOUT
1.5
Max
1.47
C
2.4
ST92163 - RESET AND CLOCK CONTROL UNIT (RCCU)
L2
VR02116A
mA/V
Unit
Table 17. Crystal Internal Resistance
Legend:
C
OSCOUT (the value includes the external capacitance
tied to the pin CL1 and CL2 plus the parasitic capacitance
of the board and of the device).
Rsmax: The equivalent serial resistor of the crystal.
Note 1: The tables are relative to the fundamental quartz
crystal only (not ceramic resonator).
Note 2: To reduce the parasitic capacitance, it is recom-
mended to place the crystal as close to the ST9 MCU as
possible.
WARNING: At low temperature, frost and humidity might
prevent the correct start-up of the oscillator.
Figure 43. Internal Oscillator Schematic
Figure 44. External Clock
Symbol Condition s C
Rsmax
(ohm)
1
, C
2
HALT
R
: Maximum Total Capacitances on pins OSCIN and
IN
OSCIN
Freq.=8MHz
Freq.=8MHz
4.0-5.5V
3.0-4.0V
EXTERNAL CLOCK
CLOCK
INPUT
OSCIN
= 56pF
50
30
1
=C
ST9
2
R
OSCOUT
= 47pF
C
NC
65
40
1
=C
2
OSCOUT
= 33pF
C
120
70
1
=C
CLOCK1
R
VR02116B
2
VR02086A
OUT
85/224
= 22pF
C
180
110
1
=C
2