EVB8720 SMSC, EVB8720 Datasheet - Page 7

• Manufacturer Part Number: EVB8720
• Description: Ethernet Modules & Development Tools LAN8720 Design BRD
• Manufacturer: SMSC

Specifications of EVB8720

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

EVB8720 Evaluation Board User Manual
SMSC EVB8720
2.2.4
nINT Mode
Off-Board
50MHz Clock
(Note
nINT Mode
On-Board
50MHz Osc.
REFCLKO
Mode
On-Board
25MHz Crystal
(Default)
REFCLKO
Mode
On-Board
50MHz Osc.
FUNCTIONAL
MODE
2.1)
Note 2.1
Internal +1.2V Regulator Configuration (REGOFF)
The LAN8720A provides the ability to disable the internal +1.2V regulator. When the regulator is
disabled, an external +1.2V must be supplied to the VDDCR pin (via TP3). Configuration of the internal
regulator is controlled by the REGOFF configuration strap. The EVB8720 must be properly configured
for each mode as follows:
Internal +1.2V Regulator Enabled (Default EVB8720 Mode)
Internal +1.2V Regulator Disabled
Note: The REGOFF configuration strap shares functionality with LED1. Therefore, LED1 may
Populate the 1-2 positions of R40 and R41 to pull-down the REGOFF strap (enable regulator).
Depopulate the 2-3 positions of R40 and R41.
Populate the 2-3 positions of R40 and R41 to pull-up the REGOFF strap (disable regulator).
Depopulate the 1-2 positions of R40 and R41.
Depopulate
Depopulate
Depopulate
Depopulate
Populate
function active-high or active-low depending on the REGOFF configuration. For additional
information on the LED1/REGOFF pin and the disabling of the internal 1.2V regulator (power
sequencing requirements, etc.), refer to the LAN8720A Datasheet and LAN8720A schematics.
R20
The off-board 50MHz clock can be routed to the CLKIN pin of the LAN8720A via the
TXCLK or RXCLK pin of the 40-pin connector. The related resistors must be populated as
shown for each mode. When using RXCLK to route the 50MHz clock to the CLKIN pin of
the LAN8720A, component U3 must be depopulated.
Table 2.3 nINT/REFCLKO Modes Resistor Configuration
Depopulate
Depopulate
Depopulate
Depopulate
Depopulate
R42,R43
Populate
Populate
Populate
Populate
Populate
1-2
2-3
1-2
2-3
1-2
2-3
1-2
2-3
1-2
2-3
Depopulate
Depopulate
Depopulate
Depopulate
Depopulate
Depopulate
Populate
Populate
Populate
Populate
USER MANUAL
R45
1-2
2-3
1-2
2-3
1-2
2-3
1-2
2-3
1-2
2-3
RELATED RESISTORS
Depopulate
Depopulate
Depopulate
Depopulate
Depopulate
Depopulate
7
Populate
Populate
Populate
Populate
R46
1-2
2-3
1-2
2-3
1-2
2-3
1-2
2-3
1-2
2-3
Depopulate
Depopulate
Depopulate
Populate
Populate
R47
Depopulate
Depopulate
Populate
Populate
Populate
R48
Depopulate
Depopulate
Depopulate
Depopulate
Populate
Revision 1.1 (05-24-10)
R49
Depopulate
Depopulate
Populate
Populate
Populate
R50