APPROVED PRODUCT
C9812
Low EMI Clock Generator for Intel 810E Chipset Systems
Power on Bi-Directional Pins
Power Up Condition:
Pin1 is a Power up bi-directional pin and is used for selecting the host frequency in page 1, table 1. During power-up of
the device, this pin is in input mode (see Fig 4, below), therefore; it is considered an input select pins internal to the IC.
After a settling time, the selection data is latch into the internal control register and this pin becomes a clock output.
VDD RAIL
POWER SUPPLY
RAMP
REF / SEL2
(Pin 1)
-
Hi-Z INPUTS
TOGGLE OUTPUTS
SELECT DATA IS LATCHED INTO REGISTER THEN PIN BECOMES A REF CLOCK OUTPUT SIGNAL
Fig.4
Strapping Resistor Options:
The power up bi-directional pins have a large value pull-down each (70KΩ), therefore, a selection “0” is the default. If the
system uses a slow power supply (over 5mS settling time), then it is recommended to use an external Pull-down in
order to insure a low selection.
Fig. 5 If a selection “0” is desired, then a jumper is placed on JP1 to a 10KΩ resistor as implemented as shown in Fig.5.
Please note the selection resistor (Rdn) is placed before the Damping resistor (Rd) close to the pin.
JP1
Vdd
Jumper
3
2
1
Rsel
10K
IMI C9812
Rd
Load
Bidirectional
Fig. 5
70K
Cypress Semiconductor Corporation
525 Los Coches St.
Document#: 38-07053 Rev. **
05/03/01
Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571
http://www.cypress.com
Page 5 of 18
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