LAN8187_06 SMSC [SMSC Corporation], LAN8187_06 Datasheet - Page 31

• Manufacturer Part Number: LAN8187_06
• Manufacturer: SMSC [SMSC Corporation]

Revision 1.0 (12-14-06)
4.9
4.9.1
4.9.2
4.10
Note: X = Dont Care.
Part of the LAN8187/LAN8187I SMSC flexPWR
regulator. This further increases the power savings as a more efficient external switching regulator can
provide the necessary +1.8v to the internal PHY circuitry.
Disable the Internal +1.8V Regulator
To disable the +1.8v internal regulator, a pulldown strapping resistor (see
Configuration Resistors,” on page
VDDA are within specification, the PHY will sample the REG_EN pin to determine if the internal
regulator should turn on. If the pin is grounded to VSS, then the internal regulator is off, and the system
needs to supply +1.8v +/- 10% to the VDD_CORE pin.
A 4.7uF low ESR and 0.1uF capacitor must be added to VDD_CORE and placed close to the PHY.
This capacitance provides decoupling of the external power supply noise and ensures stability of the
internal regulator.
Enable the Internal +1.8V Regulator
To enable the internal regulator, a pull-up resistor (see
Resistors,” on page
A 4.7uF low ESR and 0.1uF capacitor must be added to VDD_CORE and placed close to the PHY.
This capacitance provides decoupling of the external power supply noise and ensures stability of the
internal regulator.
The TX_ER, TXD4 and nINT functions share a common pin. There are two functional modes for this
pin, the TX_ER/TXD4 mode and nINT (interrupt) mode. The RXD3 pin is used to select one of these
two functional modes.
The RXD3 pin is latched on the rising edge of the internal reset (nreset) to select the mode. The
system designer must float the RXD3 pin for nINT mode or pull-low with an external resistor (see
Internal +1.8V Regulator Disable
(TX_ER/TXD4)/nINT Strapping
Figure 4.4 Direct cable connection vs. Cross-over cable connection.
32) to VDDIO needs to be added to the REG_EN pin.
±15kV ESD Protected MII/RMII Fast-Ethernet PHY with HP Auto-MDIX and SMSC flexPWR
32) is attached from REG_EN to VDDIO. When both VDDIO and
DATASHEET
31
TM
technology is the ability to disable the internal +1.8v
Table 4.4, “Boot Strapping Configuration
Table 4.4, “Boot Strapping
SMSC LAN8187/LAN8187I
Datasheet
TM