The TCA4307 is a hot-swappable I2C bus buffer that supports I/O card insertion into a live backplane without corruption of the data and clock lines. Control circuitry prevents the backplane-side I2C lines (in) from being connected to the card-side I2C lines (out) until a stop command or bus idle condition occurs on the backplane without bus contention on the card. When the connection is made, this device provides bidirectional buffering, keeping the backplane and card capacitance isolated. During insertion, the SDA and SCL lines are pre-charged to 1 V to minimize the current required to charge the parasitic capacitance of the device.
The TCA4307 has stuck bus recovery, which automatically disconnects the bus if it detects either SDAOUT or SCLOUT are low for about 40 ms. Once the bus is disconnected, the device automatically generates up to 16 pulses on SCLOUT to attempt to reset the device which is holding the bus low.
When the I2C bus is idle, the TCA4307 can be put into shutdown mode by setting the EN pin low, reducing power consumption. When EN is pulled high, the TCA4307 resumes normal operation. It also includes an open drain READY output pin, which indicates that the backplane and card sides are connected together. When READY is high, the SDAIN and SCLIN are connected to SDAOUT and SCLOUT. When the two sides are disconnected, READY is low.
PART NUMBER | PACKAGE(1) | PACKAGE SIZE(2) |
---|---|---|
TCA4307 | VSSOP (DGK, 8) | 3 mm × 4.9 mm |
WSON (DRG, 8) | 3 mm × 3 mm |
PIN | TYPE | DESCRIPTION | |
---|---|---|---|
NAME | NO. | ||
EN | 1 | I | Active-high chip enable pin. If EN is low, the TCA4307 is in a low current mode. It also disables the rise-time accelerators, disables the bus pre-charge circuitry, drives READY low, isolates SDAIN from SDAOUT and isolates SCLIN from SCLOUT. EN should be high (at VCC) for normal operation. Connect EN to VCC if this feature is not being used. |
SCLOUT | 2 | I/O | Serial clock output. Connect this pin to the SCL bus on the card. |
SCLIN | 3 | I/O | Serial clock input. Connect this pin to the SCL bus on the backplane. |
GND | 4 | - | Supply ground |
READY | 5 | O | Connection flag/rise-time accelerator control. Ready is low when either EN is low or the start-up sequence has not been completed. READY goes high when EN is high and start-up is complete. Connect a 10-kΩ resistor from this pin to VCC to provide the pull-up current. |
SDAIN | 6 | I/O | Serial data input. Connect this pin to the SDA bus on the backplane. |
SDAOUT | 7 | I/O | Serial data output. Connect this pin to the SDA bus on the card. |
VCC | 8 | - | Supply Power. Main input power supply from backplane. This is the supply voltage for the devices on the backplane I2C buses. Connect pull-up resistors from SDAIN and SCLIN (and also from SDAOUT and SCLOUT) to this supply. It is recommended to place a bypass capacitor of 0.1 μF close to this pin for best results. |
MIN | MAX | UNIT | |||
---|---|---|---|---|---|
Input Voltage | VCC | –0.5 | 7 | V | |
SDAIN, SCLIN, SDAOUT, SCLOUT | –0.5 | 7 | V | ||
EN, READY | –0.5 | 7 | V | ||
IIK | Input clamp current | VI < 0 | –50 | mA | |
IOK | Output clamp current | VO < 0 | –50 | mA | |
IO | Continuous output current | SDAIN, SDAOUT, SCLIN, SCLOUT, EN, READY | ±50 | mA | |
ICC | Continuous current through VCC or GND | ±100 | mA | ||
TJ | Maximum junction temperature | 130 | °C | ||
Tstg | Storage temperature | –65 | 150 | °C |
VALUE | UNIT | |||
---|---|---|---|---|
V(ESD) | Electrostatic discharge | Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins(1) | ±3500 | V |
Charged device model (CDM), per JEDEC specification JESD22-C101, all pins(2) | ±1000 |
MIN | MAX | UNIT | |||
---|---|---|---|---|---|
VCC | Supply voltage | 2.3 | 5.5 | V | |
VI | Input voltage range | EN input | 0 | 5.5 | |
VIO | Input/output voltage range | SDAIN, SCLIN, SDAOUT, SCLOUT | 0 | 5.5 | |
VO | Output voltage range | READY | 0 | 5.5 | |
TA | Ambient temperature | –40 | 125 | °C |
THERMAL METRIC(1) | TCA4307 | TCA4307 | UNIT | |
---|---|---|---|---|
DGK | DRG | |||
8 Pin | 8 Pin | |||
RθJA | Junction-to-ambient thermal resistance | 177.1 | 58.4 | °C/W |
RθJC(top) | Junction-to-case (top) thermal resistance | 64.5 | 61.3 | °C/W |
RθJB | Junction-to-board thermal resistance | 99.6 | 31.5 | °C/W |
ΨJT | Junction-to-top characterization parameter | 9.5 | 2.4 | °C/W |
ΨJB | Junction-to-board characterization parameter | 97.9 | 31.4 | °C/W |
RθJC(bot) | Junction-to-case (bottom) thermal resistance | N/A | 14.8 | °C/W |