NXP Semiconductors MPC5777M - Page 49

Electrical characteristics
MPC5777M Microcontroller Data Sheet, Rev. 6
NXP Semiconductors 49
Table 23. External Oscillator electrical specifications
1
1
All oscillator specifications are valid for VDD_HV_IO_JTAG = 3.0 V – 5.5 V.
Symbol Parameter Conditions
Value
Unit
Min Max
f
XTAL
CC Crystal Frequency Range
2
2
The range is selectable by UTEST miscellaneous DCF clients XOSC_LF_EN and XOSC_EN_40MHZ.
—48MHz
—>820
— >20 40
t
cst
CC Crystal start-up time
3,4
3
This value is determined by the crystal manufacturer and board design.
4
Proper PC board layout procedures must be followed to achieve specifications.
T
J
=150°C — 5 ms
t
rec
CC Crystal recovery time
5
5
Crystal recovery time is the time for the oscillator to settle to the correct frequency after adjustment of the integrated load
capacitor value.
——0.5ms
V
IHEXT
CC EXTAL input high voltage
6,7
(External Clock Input)
6
This parameter is guaranteed by design rather than 100% tested.
7
Applies to an external clock input and not to crystal mode.
V
REF
= 0.28 * V
DD_HV_IO_JTAG
V
REF
+
0.6
—V
V
ILEXT
CC EXTAL input low voltage
6,7
(External Clock Input)
V
REF
= 0.28 * V
DD_HV_IO_JTAG
—V
REF
- 0.6 V
C
S_xtal
CC Total on-chip stray capacitance
on XTAL/EXTAL pins
8
8
See crystal manufacturer’s specification for recommended load capacitor (C
L
) values.The external oscillator requires
external load capacitors when operating from 8 MHz to 16 MHz. Account for on-chip stray capacitance (C
S_EXTAL
/C
S_XTAL
)
and PCB capacitance when selecting a load capacitor value. When operating at 20 MHz/40 MHz, the integrated load
capacitor value is selected via S/W to match the crystal manufacturer’s specification, while accounting for on-chip and PCB
capacitance.
BGA416, BGA512 8 8.6 pF
V
EXTAL
CC Oscillation Amplitude on the
EXTAL pin after startup
9
9
Amplitude on the EXTAL pin after startup is determined by the ALC block, i.e., the Automatic Level Control Circuit. The
function of the ALC is to provide high drive current during oscillator startup, but reduce current after oscillation in order to
reduce power, distortion, and RFI, and to avoid over-driving the crystal. The operating point of the ALC is dependent on the
crystal value and loading conditions.
T
J
= –40 °C to 150 °C 0.5 1.6 V
V
HYS
CC Comparator Hysteresis T
J
= –40 °C to 150 °C 0.1 1.0 V
I
XTAL
CC XTAL current
13,10
10
I
XTAL
is the oscillator bias current out of the XTAL pin with both EXTAL and XTAL pins grounded. This is the maximum
current during startup of the oscillator. The current after oscillation is typically in the 2–3 mA range and is dependent on the
load and series resistance of the crystal. Test circuit is shown in Figure 13.
T
J
= –40 °C to 150 °C — 14 mA