82B715 Datasheet, PDF (5/10 Pages) NXP Semiconductors – I2C bus extender

Philips Semiconductors
I²C bus extender
Preliminary specification
82B715
RATINGS
Limiting values in accordance with the Absolute Maximum System (IEC 134).
Voltages with respect to pin GND (DIL-8 pin 4).
SYMBOL
V_CC to GND
V_bus
V_buff
I
P_tot
T_stg
T_amb
PARAMETER
Supply voltage range V_CC
Voltage range I²C Bus, SCL or SDA
Voltage range Buffered Bus
DC current (any pin)
Power dissipation
Storage temperature range
Operating ambient temperature range
CHARACTERISTICS
At T_amb = +25°C and V_CC = 5 Volts, unless otherwise specified.
SYMBOL
PARAMETER
Power Supply
V_CC
Supply voltage (operating)
I_CC
Supply current
I_CC
Supply current at V_CC = 12V
I_CC
Supply current, both I²C inputs LOW,
both buffered outputs sinking 30mA.
Drive Currents
I_Sx, I_Sy
Output sink on I²C bus
V_Sx, V_Sy LOW = 0.4V
V_Lx, V_Ly LOW on Buffered bus = 0.3V
I_Lx, I_Ly
Output sink on Buffered bus
V_Lx, V_Ly LOW = 0.4V
V_Sx, V_Sy LOW on I²C bus = 0.3V
Input Currents
I_Sx, I_Sy
Input current from I²C bus when
I_Lx, I_Ly sink on Buffered bus = 30mA
I_Lx, I_Ly
Input current from Buffered bus when
I_Sx, I_Sy sink on I²C bus = 3mA
I_Lx, I_Ly
Leakage current on Buffered bus
V_Lx, V_Ly = V_CC, and V_Sx, V_Sy = V_CC
Impedance Transformation
Z_in/Z_out
Input/Output impedance
LIMITS
MIN.
MAX.
–0.3
+12
0
V_CC
0
V_CC
60
300
–55
+125
–40
+85
UNIT
V
V
V
mA
mW
°C
°C
MIN.
4.5
—
—
—
LIMITS
TYP.
—
16
22
28
MAX.
12
—
—
—
UNIT
V
mA
mA
mA
3
—
—
mA
30
—
—
mA
—
—
3
mA
—
—
3
mA
—
—
200
µA
8
10
13
Pull-Up Resistance Calculation
In calculating the pull-up resistance values, the gain of the buffer
introduces scaling factors which must be applied to the system
components. Viewing the system from the Buffered bus, all I²C bus
capacitances have effectively 10 times their I²C bus value.
In practical systems the pull-up resistance is determined by the rise
time limit for I²C systems. As an approximation this limit will be
satisfied if the time constant (product of the net resistance and net
capacitance) of the total system is set to 1 microsecond.
The total time constant may either be set by considering each bus
node individually (i.e., the I²C nodes, and the Buffered bus node)
and choosing pull-up resistors to give time constants of 1
microsecond for each node; or by combining the capacitances into
an equivalent capacitive loading on the Buffered bus, and
calculating the Buffered bus pull-up resistor required by this
equivalent capacitance.
For each separate bus the pull-up resistor may be calculated as
follows:
R
+
1m sec
C_device ) C_wiring
Where: C_device = sum of device capacitances connected to each
bus,
and C_wiring = total wiring and stray capacitance on each bus.
If these capacitances are not known then a good approximation is to
assume that each device presents 10pF of load capacitance and
10pF of wiring capacitance.
1998 Jan 09
5