lh79524 NXP Semiconductors, lh79524 Datasheet - Page 55

• Manufacturer Part Number: lh79524
• Description: Lh79524; Lh79525 System-on-chip
• Manufacturer: NXP Semiconductors

System-on-Chip
UNUSED INPUT SIGNAL CONDITIONING
consumption. Unused inputs which do not include inter-
nal pull-up or pull-down resistors should be pulled up or
down externally, to tie the signal to its inactive state.
which carry these signals are unused, software can
program these signals as outputs, to eliminate the need
for pull-ups or pull-downs. Power consumption may be
higher than expected until such software executes.
ups or pull-downs. If unused, these inputs do not
require external conditioning.
OTHER CIRCUIT BOARD LAYOUT PRACTICES
rise and fall times. Printed circuit trace interconnection
length must therefore be reduced to minimize over-
shoot, undershoot and reflections caused by transmis-
sion line effects of these fast output switching times.
This recommendation particularly applies to the
address and data buses.
consider all device loads and capacitances due to the
circuit board traces. Capacitance due to the traces will
Preliminary data sheet
Floating input signals can cause excessive power
Some GPIO signals may default to inputs. If the pins
Some LH79524/LH79525 inputs have internal pull-
All output pins on the LH79524/LH79525 have fast
When considering capacitance, calculations must
NOTES:
1. Y1 is a parallel-resonant type crystal. (See table)
2. The nominal values for C1 and C2 shown are for
3. The values for C1 and C2 are dependent upon
4. R1 must be in the circuit.
5. Ground connections should be short and return
6. Tolerance for R1, C1, C2 is ≤ 5%.
Figure 39. Suggested External Components, 32.768 kHz Oscillator (XTAL32IN and XTAL32OUT)
a crystal specified at 12.5 pF load capacitance (CL).
the cystal's specified load capacitance and PCB
stray capacitance.
processor's core ground pins.
to the ground plane which is connected to the
INTERNAL TO
THE LH79524/LH79525
EXTERNAL TO
THE LH79524/LH79525
NXP Semiconductors
Rev. 01 — 16 July 2007
ENABLE
XTAL32IN
depend upon a number of factors, including the trace
width, dielectric material the circuit board is made from
and proximity to ground and power planes.
cuit board layout becomes more critical in systems with
higher capacitive loads. As these capacitive loads
increase, transient currents in the power supply and
ground return paths also increase.
internal pull-down resistor has been specified; see
Table 3. Consider all signals that are Inputs at Reset.
SUGGESTED EXTERNAL COMPONENTS
nents for the 32.768 kHz crystal circuit to be used with
the NXP LH79524/LH79525. The NAND gate repre-
sents the logic inside the SoC. See the table in
Figure 39 for crystal specifics.
nents for the 10 - 20 MHz crystal circuit to be used with
the NXP LH79524/LH79525. The NAND gate
resents the logic inside the SoC. See the chart for crys-
tal specifics.
Attention to power supply decoupling and printed cir-
Add pull-ups to all unused inputs unless an
Figure 39 shows the suggested external compo-
Figure 40 shows the suggested external compo-
RECOMMENDED CRYSTAL SPECIFICATIONS
32.768 kHz Crystal
Tolerance
Aging
Load Capacitance
ESR (MAX.)
Drive Level
Recommended Part
PARAMETER
C1
15 pF
GND
32.768 kHz
10 MΩ
Y1
R1
XTAL32OUT
C2
18 pF
GND
DESCRIPTION
Parallel Mode
±30 ppm
±3 ppm
12.5 pF
50 kΩ
1.0 µW (MAX.)
MTRON SX1555 or equivalent
LH79524/LH79525
LH79525-11
rep-
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