CM8500 Champion Microelectronic Corp., CM8500 Datasheet - Page 4

• Manufacturer Part Number: CM8500
• Description: 3A BUS TERMINATOR
• Manufacturer: Champion Microelectronic Corp.

FUNCTIONAL DESCRIPTION
The CM8500 is a switching regulator that is capable of sinking
and sourcing 3A of current without an external heat sink.
CM8500 uses a standard surface mount PTSSOP and PSOP
package with bottom metal exposed and the heat can be
piped through the bottom of the device and onto the PCB.
The CM8500 integrates power MOSFETs that are capable of
source and sink 3A of current while maintaining excellent
voltage regulation. The output voltage can be regulated within
3% or less by using the external feedback. Separate voltage
supply inputs have been added to fit applications with various
power supplies for the databus and power buses.
OUPUTS
The output voltage pins (VL1, VL2) are tied to the databus,
address, or clock lines via an external inductor. Output voltage
is determined by the VCCQ or VIN/2 inputs.
APPLICATIONS
USING THE CM8500 FOR SSTL BUS TERMINATION
Figure 1 is the typical schematic of the CM8500TEVAL that
shows the recommended approach for bus terminating
solutions for SSTL-2 bus. This circuit can be used in PC
memory and Graphics memory applications as shown in
Figure 2 and Figure 3.
Figure 4 shows the PCB layout of the CM8500TEVAL.
Table 1details the key parameters of SSTL_2 specification.
Figure 5 shows two different approach of SSTL_2 Terminated
Output. (Refer to page 8 for detail description.)
2004/06/01
Rev. 1.1
Champion Microelectronic Corporation
INPUTS
The input voltage pins (VCCQ or VIN/2) determine the output
voltages (VL1 or VL2). In the default mode, when the VIN/2 pin
is open, the output voltage is 50% of the VCCQ input.
If a specific voltage is forced at the VIN/2 pin, the output voltage
follows the voltage at the VIN/2 pin. VCCQ suggested
connecting to VCCQ of memory module for better tracking with
memory VCCQ.
OTHER SUPPLY VOLTAGES
Several inputs are provided for the supply voltages: PVDD1,
PVDD2, VCC1, and VCC2.
The PVDD1 and PVDD2 provide the power supply to the power
MOSFETs. VCC1 and VCC2 provide the voltage supply to the
logic section and internal error amplifiers.
FEEDBACK
The VFB pin is an input that can be used for closed loop
compensation. This input is derived from the voltage output.
AGSEN pin is a contact node of internal resistor divider for
remote sense.
3A B
US
T
ERMINATOR
CM8500
Page 4