S P I/Mic ro w ire -Co m p a t ib le
UART in QS OP -1 6
ISO +5V
+5V
2k
V
CC
V
CC
TX
RX
CS
SCLK
DIN
CS
470Ω
SCLK
DIN
MAX310
MAX3100
MAX3100
DOUT
DOUT
+5V
2k
RX
TX
GND
GND
470Ω
Figure 8. Bidirectional Opto-Isolated Interface
Table 8. Component and Supplier List
FREQUENCY
(MHz)
TYPICAL
C1, C2 (pF)
PART
NUMBER
PHONE
NUMBER
DESCRIPTION
SUPPLIER
Through-Hole Crystal
(HC-49/U)
1.8432
1.8432
25
ECS International, Inc.
Murata North America
ECS-18-13-1
CSA1.84MG
(913) 782-7787
(800) 831-9172
Through-Hole
Resonator
47
Through-Hole Crystal
(HC-49/US)
3.6864
3.6864
3.6864
33
39
ECS International, Inc.
ECS International, Inc.
AVX/Kyocera
ECS-36-18-4
ECS-36-20-5P
PBRC-3.68B
(913) 782-7787
(913) 782-7787
(803) 448-9411
SMT Crystal
None
(integral)
SMT Resonator
This oscillator supports parallel-resonant mode crystals
a nd c e ra mic re s ona tors , or c a n b e d rive n from a n
external clock source. Internally, the oscillator consists
of an inverting amplifier with its input, X1, tied to its out-
put, X2, by a bias network that self-biases the inverter
ified load capacitance of 11pF would use capacitors of
22pF on either side of the crystal to ground. Series-res-
onant mode crystals have a slight frequency error, typi-
cally oscillating 0.03% higher than specified series-
resonant frequency, when operated in parallel mode.
at approximately V / 2. The external feedback circuit,
CC
It is very important to keep crystal, resonator, and
load-capacitor leads and traces as short and direct as
possible. The X1 and X2 trace lengths and ground
tracks should be tight, with no other intervening traces.
This helps minimize parasitic capacitance and noise
pickup in the oscillator, and reduces EMI. Minimize
capacitive loading on X2 to minimize supply current.
usually a crystal, from X2 to X1 provides 180° of phase
shift, causing the circuit to oscillate. As shown in the
standard application circuit, the crystal or resonator is
connected between X1 and X2, with the load capaci-
tance for the crystal being the series combination of C1
and C2. For example, a 1.8432MHz crystal with a spec-
14 ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
