LTC4300A-1/LTC4300A-2

10

sn4300a12 4300a12fs

Resistor Pull-Up Value Selection

The system pull-up resistors must be strong enough to

provide a positive slew rate of 1.25V/

µs on the SDA and

SCL pins, in order to activate the boost pull-up currents

during rising edges. Choose maximum resistor value R

using the formula:

R

capacitance in picofarads (pF).

APPLICATIO S I FOR ATIO

In addition, regardless of the bus capacitance, always

choose R

high voltages on SDAOUT and SCLOUT to connect the

backplane to the card, and these pull-up values are needed

to overcome the precharge voltage.

Live Insertion and Capacitance Buffering Application

Figures 3 through 6 illustrate the usage of the LTC4300A

in applications that take advantage of both its hot swap

controlling and capacitance buffering features. In all of

Figure 3. Inserting Multiple I/O Cards into a Live Backplane Using the LTC4300A-1 in a CompactPCI System

R13

10k

R12

10k

R14

10k

I/O PERIPHERAL CARD N

ENABLE

SDAIN

SCLIN

U3

LTC4300A-1

GND

CARDN_SCL

CARDN_SDA

SDAOUT

SCLOUT

READY

ENABLE

SDAIN

SCLIN

GND

SDAOUT

SCLOUT

READY

ENABLE

CARD

ENABLE/DISABLE

SDAIN

SCLIN

GND

SDAOUT

SCLOUT

READY

4300A-1/2 F03

R9

10k

R8

10k

R10

10k

I/O PERIPHERAL CARD 2

U2

LTC4300A-1

CARD2_SCL

CARD2_SDA

R5

10k

R4

10k

R6

10k

I/O PERIPHERAL CARD 1

U1

LTC4300A-1

CARD_SCL

CARD_SDA

R1

10k

R2

10k

BACKPLANE

BACKPLANE

CONNECTOR

SDA

BD_SEL

SCL

C1

0.01

µF

R3

10k

R7

10k

R11

10k

C3

0.01

µF

C5

0.01

µF

POWER SUPPLY

HOT SWAP

POWER SUPPLY

HOT SWAP

POWER SUPPLY

HOT SWAP

CARD

ENABLE/DISABLE

CARD

ENABLE/DISABLE