LTC6906 datasheet(21/28 Pages) AD

21 / 28 page

LTC6994-1/LTC6994-2

Rev. C

For more information www.analog.com

699412 F16

LTC6994

GND

SET

OUT

V+

DIV

0.1µF

RSET

V+

DIV

SET

OUT

GND

V+

RSET

DCB PACKAGE

GND

SET

OUT

V+

DIV

V+

RSET

TSOT-23 PACKAGE

APPLICATIONS INFORMATION

Figure 16. Supply Bypassing and PCB Layout

Supply Bypassing and PCB Layout Guidelines

TheLTC6994isanaccuratemonostablemultivibratorwhen

used in the appropriate manner. The part is simple to use

and by following a few rules, the expected performance is

easily achieved. Adequate supply bypassing and proper

PCB layout are important to ensure this.

Figure 16 shows example PCB layouts for both the SOT-23

and DCB packages using 0603 sized passive components.

The layouts assume a two layer board with a ground plane

layer beneath and around the LTC6994. These layouts are

a guide and need not be followed exactly.

1. Connect the bypass capacitor, C1, directly to the V+ and

GND pins using a low inductance path. The connection

from C1 to the V+ pin is easily done directly on the top

layer. For the DCB package, C1’s connection to GND is

also simply done on the top layer. For the SOT-23, OUT

can be routed through the C1 pads to allow a good C1

GND connection. If the PCB design rules do not allow

that,C1’sGNDconnectioncanbeaccomplishedthrough

multiple vias to the ground plane. Multiple vias for both

the GND pin connection to the ground plane and the

C1 connection to the ground plane are recommended

to minimize the inductance. Capacitor C1 should be a

0.1µF ceramic capacitor.

2. Place all passive components on the top side of the

board. This minimizes trace inductance.

3. Place RSET as close as possible to the SET pin and make

adirect,shortconnection.TheSETpinisacurrentsum-

ming node and currents injected into this pin directly

modulate the output delay. Having a short connection

minimizes the exposure to signal pickup.

4. Connect RSET directly to the GND pin. Using a long path

or vias to the ground plane will not have a significant

affect on accuracy, but a direct, short connection is

recommended and easy to apply.

5. Use a ground trace to shield the SET pin. This provides

another layer of protection from radiated signals.

6. Place R1 and R2 close to the DIV pin. A direct, short

connection to the DIV pin minimizes the external signal

coupling.

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