TransDimension Inc.
Interfacing TD242LP to Intel StrongArm SA1110 Processor
TD242LP
6.000 MHz
OSC1
10pF
10pF
100
OSC2
Figure 7: TD242LP crystal oscillator circuit
To assure a quick start of the internal PLL circuitry, a crystal with a high Q, or low ESR, should
be used. To meet the USB frequency accuracy and stability requirements, the crystal should have
an accuracy and stability of better than 2500 PPM.
An external 6 MHz parallel resonance quartz crystal is required for TD242LP’s built-in
oscillator. If the crystal cannot tolerate the drive levels of the oscillator, a series resistor between
OSC2 and the crystal pin is recommended per Figure 7. Please refer to the crystal manufacturer’s
specification.
Alternative clock input for the BGA64
6MHz is the only crystal oscillator frequency supported. However, the BGA64 supports two
alternative clock inputs. First is a single-ended 6MHz oscillator, with a 2.5V output, connected to
OSC1. OSC2 must be tied to ground. Second is a single-ended 12MHz, 24MHz, or 48MHz
oscillator, also with a 2.5V output, connected to OSC2. OSC1 must be tied to 3.3V. Coming out
of RESET, the VBP pin and the CLKCFG pin are sampled to determine the frequency used per
the table below. The TD242LP does not distinguish between a 6MHz crystal and a 6MHz single-
ended oscillator. Do not use this table for the LQFP64 package.
VBP
CLKCFG
6MHz
0
0
1
1
0
1
1
0
12MHz
24MHz
48MHz
Figure 8: Frequency Selection for the BGA64 package
TransDimension, Inc.
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