AT43301
4
Functional Description
Summary
The Atmel AT43301 USB hub controller chip contains vari-
ous features that makes it the ideal solution for very low-
cost USB hubs. These features are: on-chip regulator, low-
frequency oscillator, bus or self-powered operation,
ganged port power switching and global overcurrent pro-
tection. Such a hub can be a stand-alone hub used with
portable computers to allow convenient connectivity to
standard desktop peripheral devices. Alternatively, the hub
can be added to an existing non-USB peripheral such a
keyboard. The AT43301 provides 4 downstream USB ports
and can operate in a self-powered or bus-powered mode.
USB Ports
The AT43301’s upstream port, Port0, is a full speed port. A
1.5 k
Ω
pull-up resistor to the 3.3V regulator output, CEXT,
is required for proper operation. The downstream ports
support both full-speed as well as low-speed devices.
15 k
Ω
pull down resistors are required at their inputs.
Full spee d signal requirements de mand controlled
rise/fall times and impedance matching of the USB ports.
To meet these requirements, 22
Ω
resistors must be
inserted in series between the USB data pins and the USB
connectors.
Table 3. Signal Descriptions
CEXT1
O
External Capacitor. For proper operation of the on-chip regulator, a 0.27
µ
F capacitor must be connected to
CEXT1.
DP0
B
Upstream Plus USB I/O. This pin should be connected to the CEXT1 pin through an external 1.5 k
Ω
pull-up
resistor. DP0 and DM0 form the differential signal pin pairs connected to the USB host controller or an
upstream Hub.
DM0
B
Upstream Minus USB I/O.
DP[1:4]
B
Port Plus USB I/O. This pin should be connected to VSS through an external 15 k
Ω
resistor. DP[1:4] and DM[1:4]
are the differential signal pin pairs to connect downstream USB devices.
DM[1:4]
B
Port Minus USB I/O. This pin should be connected to VSS through an external 15 k
Ω
resistor.
LFT
I
PLL Filter. For proper operation of the PLL, this pin should be connected through a 2.2 nF capacitor in parallel
with a 100
Ω
resistor in series with a 10 nF capacitor to ground (VSS).
LPSTAT
I
Local Power Status. Schmitt Trigger input pin that is used in the self-powered mode to indicate the condition of
the local power supply. This pin should be connected to the local power supply through a 100 k
Ω
resistor.
OSC1
I
Oscillator Input. Input to the inverting 6 MHz oscillator amplifier.
OSC2
O
Oscillator Output. Output of the inverting oscillator amplifier.
OVC
I
Port Overcurrent. This is the Schmitt Trigger input signal used to indicate to the AT43301 that there is a power
supply problem with the ports. If OVC is asserted, the AT43301 will de-assert PWR and report the status to the
USB Host.
PWR
O
Power Switch. This is an output signal to enable or disable the external port power switch for the port power
supply. PWR is de-asserted when an overcurrent is detected at OVC.
SELF/BUS
I
Power Mode. Schmitt Trigger input pin to set power mode of hub. If high, the AT43301 works in the self-powered
mode. If low, the bus-powered mode.
STAT
O
Status. Output pin which is asserted by the AT43301 whenever it is enumerated. STAT is de-asserted when the
hub enters the suspend state. An LED in series with a resistor can be connected to this pin to provide visual
feedback to the user.
TEST
I
Test. This pin has an internal pull up and should be left unconnected in the normal operating mode.
VCC
V
5V Power Supply from the USB.
VSS
V
Ground.
NC
-
No Connect. This pin should be left unconnected.
