USB-SPI-DIL HEXWAX, USB-SPI-DIL Datasheet - Page 5

• Manufacturer Part Number: USB-SPI-DIL
• Description: IC, BRIDGE, USB-SERIAL SPI, DIL28
• Manufacturer: HEXWAX

Specifications of USB-SPI-DIL

• Digital Ic Case Style: DIP
• No. Of Pins: 28
• Package / Case: DIL
• Termination Type: Through Hole
• Supply Voltage Range: 2.7V To 5.5V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application Circuits
The following circuits are typical implementations of the
USB-SPI. Suggested component values are shown in
table 5. For initial evaluation, the Bus Powered Device
circuit is recommended.
Bus Powered Device
Figure 2 is the suggested circuit when initially evaluating
USB-SPI.
The microcontroller sends and receives data via its SPI
pins MISO, MOSI, SCK and SS#. The Rx Buff Not Full
and Tx Buffer Full can be monitored if required for flow
control. When Rx Buffer Not Full is low, no data should
be sent to the USB-SPI. If Tx Buff Empty is high and
the microcontroller reads data from USB-SPI, then Null
Tx Char will be read.
microcontroller and the rest of the circuit should go into
a sleep state.
The pushbutton circuits allow you to apply logic 1 or
logic 0 to input pins. The LED circuits allow you to view
the state of output pins. As shown they are active low.
For commercial applications these circuits need only be
provided if required.
p5 of 9
Vdd
Vss
Vdd
(Active low shown)
circuit for each input
One LED circuit
(Active low shown)
for each output
R4, R5, R30, R50
One pushbutton
Figure 2
PB1x
R1-R2, R1x
R2x
C4, C6-C7
R1x
D1, D2
C2, C3
LED1x
T1, T2
Label
PB1x
R2x
R40
R6
C1
C8
X1
C8
Table 5. Suggested component values
Vdd
Vss
Rx Ind
Tx Ind
AllSysGo#
Reset#
Send
C7
Vusb
TEAclipper
connector
C6
26-Aug-10
C1
Microcontroller
P-channel Mosfet, e.g. NDS352P
1
2
USB-SPI
12MHz parallel cut crystal
Host
3
Low Vf switching diode
When it ShtDn# low, the
Pushbutton or switch
4
Light emitting diode
100nF capacitor
470nF capacitor
5
22pF capacitor
470Ω resistor
1μF capacitor
100k resistor
Component
22k resistor
4k7 resistor
1k resistor
Vss
OSC2
OSC1
D+
D-
Vss
Vdd
Vdd
Vss
X1
C3
C2
USB-SPI
4
3
2
1
Vss
USB
Oscillator X1/C2/C3 may be replaced by a low-cost
resonator, provided its frequency tolerance is greater
than 0.25%. C1 and C6 should be placed close to the
USB connector. C7 should be placed near the Vss and
Vdd pins of the USB-SPI and is required only if it would
be some distance from C6. C8 is a filter capacitor for an
internal regulator and is required.
The TEAclipper connector is for in-circuit programming
of devices where the firmware has been purchased from
HexWax. It is recommended to allow firmware updates,
even if the firmware is initially supplied pre-programmed.
Self Powered Device
A self-powered device does not need to draw power
from the USB bus. In this case, the USB-SPI can be put
into sleep mode when USB power is not available. The
sub-circuit required to do this is shown in figure 3. If the
device is self-powered, it is not necessary to enter the
sleep state if the Suspend indicate is active.
Both-powered Powered Device
If both self-powered and bus powered configurations are
possible, a circuit must be provided to switch over power
to USB power. An example sub-circuit is given in figure
4, where it is assumed that USB power is used when it
is available. To give self-power priority, place T2 so that
it switches the USB power line instead. D1 and D2
ensure that the two power lines are not in contention. If
the self-power source is 3.3V, the diodes will be
sufficient and T2 will not be required at all.
Power Take-Off
A device should only draw current from the USB line
once USB configuration is complete and the host PC is
not is sleep mode. The AllSysGo# output (active low)
can provide such a switch using the sub-circuit shown in
figure 5. C4 / R6 provide a slow switch-on to prevent
inrush current exceeding USB power limitations. 1μF
and 100nF smoothing capacitors are recommended on
both self and USB power lines. The Low Pwr output
USB-Power Vdd
Figure 4
Self-Power Vdd
3.3V - 5V
HW144-7
Figure 3
USB-SPI
Vss
USB Pwr Sns
R40
R30
USB Pwr
Sns
Vdd
Vss
D+
D-
T2
Self Power Source
USB-SPI
Vdd
D1
D2
R3
R4
Vss
Vdd
4
3
2
1
Self Pwr
www.hexwax.com
Sns
USB
Vss
R50