LM2507 datasheet(14/22 Pages) NSC

14 / 22 page

Functional Description (Continued)

LM2507 Features and Operation

POWER SUPPLIES

The V

DDcore and VDDA (MPL and PLL) must be connected to

the same potential between 1.74V and 2.0V. V

DDIO powers

the logic interface and may be powered between 1.74 and

3.0V to be compatible with a wide range of host and target

devices. On this device, V

DDIO must be powered up be-

fore V

DDcore/VDDA

for proper device configuration/

startup.

BYPASS RECOMMENDATIONS

Bypass capacitors should be placed near the power supply

pins of the device. Use high frequency ceramic (surface

mount recommended) 0.1 µF capacitors. A 2.2 to 4.7 µF

Tantalum capacitor is recommended near the Master V

DDA

pin for PLL bypass. A 2.2 to 4.7 µF Tantalum capacitor is

recommended near the Slave V

DDA pin for MPL bypass.

Connect bypass capacitors with wide traces and use dual or

larger via to reduce resistance and inductance of the feeds.

Utilizing a thin spacing between power and ground planes

will provide good high frequency bypass above the fre-

quency range where most typical surface mount capacitors

are less effective. To gain the maximum benefit from this, low

inductance feed points are important. Also, adjacent signal

layers can be filled to create additional capacitance. Mini-

mize loops in the ground returns also for improved signal

fidelity and lowest emissions.

UNUSED/OPEN PINS

Unused inputs must be tied to the proper input level — do

not float them. Unused outputs should be left open to mini-

mize power dissipation.

PHASE-LOCKED LOOP

When the LM2507 is configured as a CPU Master, a PLL is

enabled to generate the serial link clock. The Phase-locked

loop system generates the serial data clock at 4X of the input

clock. The MC rate is limited between 12MHz and 80MHz

which corresponds to an input CLK of 3 to 20MHz.

MASTER(SER)/SLAVE(DES) SELECTION

The M/S* pin is used to configure the device as either a

Master or Slave device. When the M/S* pin is a Logic High,

the Master / Serializer configuration is selected. The Driver

block is enabled for the MC line, and the MD lines. When the

M/S* pin is a Logic Low, the Slave / Deserializer configura-

tion is selected. The Receiver block is enabled for the MC

line, and the MD lines.

POWER DOWN/OFF CONFIGURATION / OPTIONS AND

CLOCK STOP

Power Up Operation - Upon the application of power to the

LM2507, devices configured for Slave activate all outputs.

Outputs are held in deasserted states, with all zeros on the

data busses until valid data is received from the Master

device. If PD* is asserted (Low) prior to the application of

power, then the part remains in its power down state.

20186028

FIGURE 14. Two WRITE Timing – Master IN vs. Slave OUT

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