5
AN1176.0
June 20, 2005
USB connector (CN1). This connector is a standard USB
type B connector which goes to the USB port of a PC using a
USB type A-B cable.
LEDs
There are three surface-mounted LEDs on the board. LED2
and LED3 monitor the TX and RX functions of the serial port.
They should be observed to insure that communication is
taking place with the serial port. LED1 monitors the power
supply and will light when the +5V power is applied from the
USB cable.
ISL1208 Daughtercard - Functional Description
(see Figure 4)
The ISL1208 daughtercard contains the ISL1208 device,
crystal, decoupling capacitor, temp-sensor, and an LED
(D1), for monitoring the open drain output.
FIGURE 4. ISL1208 DAUGHTERCARD
POWER
Jumper JP1 connects to the V
CC
pin of the ISL1208 device
and must have a shunt in place for the device to function in
normal mode.
OPEN DRAIN OUTPUT
The open drain output of the ISL1208 is the IRQ-F
OUT
signal. There is a jumper (JP2) which connects D1 when a
shunt is in place, and also enables hooking up an external
pullup resistor if it is desired to use the logic signal. The
pullup resistor should terminate to a voltage that is less than
or equal to V
CC
.
CRYSTAL
A standard 32.768kHz surface-mounted crystal is supplied
on the daughtercard. A through-hole device can only be
attached by surface mounting the leads after the surface
mount device is removed.
TEMPERATURE SENSOR
There is an LM76 temperature sensor on the board which
measures ambient temperature, digitizes it, and provides it
to the microcontroller when prompted. Mounting on the
daughtercard enables remote sensing of temperature should
the daughtercard be placed in a temp chamber and wired to
the motherboard.
MEASUREMENTS
The V
CC
supply current may be monitored by adding a
series ammeter to JP1. D1 provides visual indication of IRQ-
F
OUT
status, and at low frequencies it will indicate that F
OUT
is enabled. At higher F
OUT
frequencies it is possible to
monitor the pin with an oscilloscope. This allows good
monitoring of the crystal frequency, up to 32kHz. It is
possible to probe the X2 oscillator output with a scope
probe, but this is not recommended as it alters the oscillator
frequency or possibly stop it momentarily due to introduction
of a transient. If it is absolutely necessary to monitor the
oscillator output, use a low-capacitance probe (<2pF) or an
active probe and note that the absolute frequency monitored
will be higher than that without the probe.
ISL1209 Daughtercard - Functional Description
(see Figure 5)
The ISL1209 daughtercard contains the ISL1209 device,
crystal, decoupling capacitor, temp-sensor, and an LED
(D1), for monitoring the open drain output, similar to the
ISL1208 daughtercard. In addition there is a microswitch,
S1, and a connection block, J3, for the event-detect function.
Also, another LED (D2) is available for event monitoring.
The main functions of this daughtercard are similar to the
ISL1208. The important differences are discussed here.
EVENT-DETECT SWITCH, S1
This is a normally CLOSED switch which is typically
connected to ground. A shunt should be installed on J3 from
the EVT to GND position for this purpose. Depressing the
switch with the event detection software enabled will cause
an event to be recorded.
EVENT-DETECT OUTPUT
The event-detect output is open-drain and can be connected
to LED D2 by placing a shunt on JP3. With this output
enabled, the LED will light when an event occurs.
EVENT CONNECTION BLOCK
J3 contains all signals needed to connect a remote event
generating circuit to the evaluation board. V
CC
, V
BAT
, the
EVIN device input (labeled EVI), Ground, and a high value
pulldown resistor are all brought to this block. The 6
th
Application Note 1176
