Datasheet

Micrel, Inc. KS8721BL/SL
June 2009
18
M9999-062509-1.3
Circuit Design Reference for Power Supply
Micrel’s integrated built-in, voltage regulator technology and thoughtful implementation allows the user to save BOM
cost on both existing and future designs with the use of the new KS8721BL/SL single supply, single port 10/100
Ethernet PHY.
7
24
+3.3V
KS8721BL/SL
8 12233536394344
VDDI/O
VDDI/O
VDDC VDDPLL
Voltage
Regulator
10F
+2.5V +2.5VPLL
Ferrite Bead
10F
10F 10F
13 47
+2.5VA
Ferrite Bead
VDDTX
OUTIN
GND
42 31 38
10F 10F
VDDRX
VDDRCV
Figure 4. Circuit Design
The circuit design in Figure 4 shows the power connections for the power supply: the 3.3V to VDDI/O is the only input
power source and the 2.5V at VDDRCV, pin 38, is the output of the voltage regulator that needs to supply through the
rest of the 2.5V VDD pins via the 2.5V power plane.
The 2.5V VDD pins make the drop-in replacement with the existing KS8721B/BT part. Table 2 shows the drop-in
replacement from the existing KS8721B/BT to the KS8721SL/BL. Please contact your local Micrel FAE for Application
Note AN-117, “Drop-in Replacement with KS8721BT.”
2.5V/3.3V Supply 3.3V Supply with Built-in Regulator
Part Number Package Part Number Package
KS8721B 48-SSOP KS8721SL 48-SSOP
KS8721BT 48-TQFP KS8721BL 48-LQFP
KS8721BI 48-SSOP KS8721SLI 48-SSOP
Table 2. Drop-In Replacement