USBN9604-28MX National Semiconductor, USBN9604-28MX Datasheet - Page 8

• Manufacturer Part Number: USBN9604-28MX
• Description: IC,Bus Controller,SOP,28PIN
• Manufacturer: National Semiconductor

Specifications of USBN9604-28MX

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

1.0 Signal/Pin Connection and Description
1.2 DETAILED SIGNAL/PIN DESCRIPTIONS
1.2.1
1.2.2
Oscillator Circuit
The XIN and XOUT pins may be connected to make a 24 MHz closed-loop, crystal-controlled oscillator. Alternately, an ex-
ternal 24 MHz clock source may be used as the input clock for the device. The internal crystal oscillator uses a 24 MHz
fundamental crystal. See Table 1 for typical component values and Figure 1 for the crystal circuit. For a specific crystal,
please consult the manufacturer for recommended component values.
If an external clock source is used, it is connected to XIN. XOUT should remain unconnected. Stray capacitance and induc-
tance should be kept as low as possible in the oscillator circuit. Trace lengths should be minimized by positioning the crystal
and external components as close as possible to the XIN and XOUT pins.
I/O
NA
NA
I/O
NA
NA
NA
NA
O
I
Power Supply
Oscillator, Clock and Reset
XIN
XOUT
CLKOUT Clock Output. This programmable clock output may be disabled and configured for different
RESET
Vcc
GND
AGND Analog Power Supply (AGND)
V3.3
Name
Name
Crystal Resonator
Resistor R1
Digital Power Supply (V
level as GND and then raised to the required V
to be set to their reset values, the clock generator to be reset and stalls the CLKOUT output for
2
Digital Power Supply (GND)
Transceiver 3.3V Voltage Supply. This pin can be used as the internal 3.3V voltage regulator
output. The regulator is intended to power only the internal transceiver and one external pull-up.
An external 1 F de-coupling capacitor is required on this pin. The voltage regulator output is dis-
abled upon reset. When the internal voltage regulator is left disabled, this pin must be used as a
3.3V supply input for the internal transceiver. This is the case during 3.3V operation.
14
Component
Crystal Oscillator Input. Input for internal 24 MHz crystal oscillator circuit. A 24 MHz funda-
mental crystal may be used.
Crystal Oscillator Output
speeds via the Clock Configuration register. After a power-on reset and hardware reset (as-
sertion of RESET), a 4 MHz clock signal is output (there may be an initial phase discontinuity).
In the USBN9604, a hardware reset causes CLKOUT to stall for 2
internal DLL is synchronized to the external reference clock.
Reset. Active low, assertion of RESET indicates a hardware reset, which causes all registers
in the device to revert to their reset values.
In the USBN9604, the hardware reset action is identical to a power-on reset. Signal condition-
ing is provided on this input to allow use of a simple, RC power-on reset circuit.
XIN clock cycles. During this time, no internal register is accessible.
Table 1. Approximate Component Values
Resonance Frequency
Type
Maximum Serial Resistance
Maximum Shunt Capacitance
Load Capacitance
CC
). Power-on reset is detected when the input voltage is at the same
Parameters
7
(Continued)
Description
Description
cc
level. The power-on reset causes all registers
24 MHz
Values
AT-Cut
10 pF
20 pF
1 M
50
14
XIN clock cycles while the
Tolerance
2500 ppm
(max)
5%
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