Si8440/41/42/45

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2.3. Device Operation

Device behavior during start-up, normal operation, and shutdown is shown in Table 12. Table 13 provides an

overview of the output states when the Enable pins are active.

Table 12. Si84xx Logic Operation Table

VI

Input1,2

EN

Input1,2,3,4

VDDI

State1,5,6

VDDO

State1,5,6

VO Output1,2

Comments

HH or NC

P

P

H

Enabled, normal operation.

LH or NC

P

P

L

X7

L

P

P

Hi-Z or L8

Disabled.

X7

H or NC

UP

P

L

Upon transition of VDDI from unpowered to pow-

ered, VO returns to the same state as VI in less

than 1 µs.

X7

L

UP

P

Hi-Z or L8

Disabled.

X7

X7

P

UP

Undetermined

Upon transition of VDDO from unpowered to pow-

ered, VO returns to the same state as VI within

1 µs, if EN is in either the H or NC state. Upon

transition of VDDO from unpowered to powered,

VO returns to Hi-Z within 1 µs if EN is L.

Notes:

1. VDDI and VDDO are the input and output power supplies. VI and VO are the respective input and output terminals. EN

is the enable control input located on the same output side.

2. X = not applicable; H = Logic High; L = Logic Low; Hi-Z = High Impedance.

3. It is recommended that the enable inputs be connected to an external logic high or low level when the Si84xx is

operating in noisy environments.

4. No Connect (NC) replaces EN1 on Si8440/45. No Connect replaces EN2 on the Si8445. No Connects are not internally

connected and can be left floating, tied to VDD, or tied to GND.

5. “Powered” state (P) is defined as 2.70 V < VDD < 5.5 V.

6. "Unpowered" state (UP) is defined as VDD = 0 V.

7. Note that an I/O can power the die for a given side through an internal diode if its source has adequate current.

8. When using the enable pin (EN) function, the output pin state is driven to a logic low state when the EN pin is disabled

(EN = 0) in Revision C. Revision D outputs go into a high-impedance state when the EN pin is disabled (EN = 0). See

"3. Errata and Design Migration Guidelines" on page 24 for more details.