ISL33001IRTZ-T Intersil, ISL33001IRTZ-T Datasheet - Page 10
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ISL33001IRTZ-T
Manufacturer Part Number
ISL33001IRTZ-T
Description
IC BUS BUFF HOTSWAP 2WR 8TDFN
Manufacturer
Intersil
Type
I²C-Bus and SMBus Switchr
Datasheet
1.ISL33001IUZ.pdf
(19 pages)
Specifications of ISL33001IRTZ-T
Applications
General Purpose, Buffer/Bus Extender
Internal Switch(s)
Yes
Voltage - Supply
2.3 V ~ 5.5 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
8-WDFN Exposed Pad
For Use With
ISL33001MSOPEVAL1Z - EVAL BOARD ISL33001 8MSOP
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Coming out of UVLO but prior to a valid connection state,
the SDA and SCL pins are pre-charged to 1V to allow hot
insertion. Because the bus at any time can be between
0V and V
maximum differential voltage from the buffer I/O pin and
the active bus. The pre-charge circuitry reduces system
disturbance when the IC is hot plugged into a live back
plane that may have the bus communicating with other
devices.
Note - For ISL33001 and ISL33003 with EN pins, the
pre-charge circuitry is active only after coming out of
UVLO and having the device enabled.
Connection Circuitry
Once a valid connection condition is met, the buffer is
active and the input stage of the SDA/SCL pins is
controlled by external drivers. The output of the buffer
will follow the input of the buffer. The directionality of the
IN/OUT pins are not exclusive (bi-directional operation)
and functionally behave identical to each other. Being a
two channel buffer, the SDA and SCL pins also behave
identically. In addition, the SDA and SCL portions of the
buffer are independent from each other. The SDA pins
can be driven in one direction while the SCL pins can be
driven opposite.
Refer to Figure 8 for the operation of the bi-directional
buffer. When the input stage of the buffer on one side is
driven low by an external device, the output of the buffer
drives an open-drain transistor to pull the ‘output’ pin
low. The ‘output’ pin will continue to be held low by the
transistor until the external driver on the ‘input’ releases
the bus.
To prevent the buffer from entering a latched condition
where both internal transistors are actively pulling the
I/O pins low, the buffer is designed to be active in only
one direction. The buffer logic circuitry senses which
input stage is being externally driven low and sets that
buffer to be the active one. For example, referring to
Figure 8, if SDA_OUT is externally driven low, buffer U2
will be active and buffer U1 is inactive. M1 is turned on to
drive SDA_IN low, effectively buffering the signal from
SDA_OUT to SDA_IN. The low signal at the input of U1
will not turn M2 on because U1 remains inactive,
preventing a latch condition.
Buffer Output Low and Offset Voltage
By design, when a logic input low voltage is forced on the
input of the buffer, the output of the buffer will have an
input to output offset voltage. The output voltage of the
buffer is determined by Equation 1:
V
Where V
the pull up resistance on the SDA/SCL pin to V
R
pull-down device. The last term of the equation is the
additional voltage drop developed by sink current and
the internal resistance of the transistor. The V
buffer can be determined by Figures 17, 18 and is
OUT
ON
is the ON resistance of the buffer’s internal NMOS
=
V
OS
CC
IN
+
is the buffer internal offset voltage, R
, pre-charging the I/O pins to 1V reduces the
V
OS
+
[
V
CC
⁄
R
PULL-UP
10
×
ISL33001, ISL33002, ISL33003
R
ON
]
OS
CC
Pull-Up
of the
and
(EQ. 1)
is
typically 40mV. Reducing the pull-up resistor values
increases the sink current and increases the output
voltage of the buffer for a given input low voltage
(Figures 15, 16, 17, 18).
Rise Time Accelerators
The ISL33001, ISL33002, ISL33003 buffer rise time
accelerators on the SDA/SCL pins improve the transient
performance of the system. Heavy load capacitance or
weak pull-up resistors on an Open-Drain bus cause the
rise time to be excessively long, which leads to data
errors or reduced data rate performance. The rise time
accelerators are only active on the low to high transitions
and provide an active constant current source to slew the
voltage on the pin quickly (Figure 19).
The rise time accelerators are triggered immediately
after the buffer release threshold (approximately 30% of
V
triggered, the accelerators are active for a defined pulse
width (Figure 20) with the current source turning off as it
approaches the supply voltage.
Enable Pin (ISL33001 and ISL33003)
When driven high, the enable pin puts the buffer into its
normal operating state. After power-up, EN high will
activate the bus pre-charge circuitry and wait for a valid
connection state to enable the buffer and the accelerator
circuitry.
Driving the EN pin low disables the accelerators, disables
the buffer so that signals on one side of the buffer will be
isolated from the other side, disables the pre-charge
circuit and places the device in a low power shutdown
state.
READY Logic Pin (ISL33001 Only)
The READY pin is a digital output flag for signaling the
status of the buffer. The pin is the drain of an Open-Drain
NMOS. Connect a resistor from the READY pin to V
provide the high pull-up. The recommended value is
10kΩ.
When the buffer is disabled by having the EN pin low or if
the start-up sequencing is not complete, the READY pin
will be pulled low by the NMOS. When the buffer has the
EN pin high and a valid connection state is made at the
SDA/SCL pins, the READY pin will be pulled high by the
pull-up resistor. The READY pin is capable of sinking 3mA
when pulled low while maintaining a voltage of less than
0.4V.
ACC Accelerator Pin (ISL33002 Only)
The ACC logic pin controls the rise time accelerator
circuitry of the buffer. When ACC is driven high, the
accelerators are enabled and will be triggered when
crossing the buffer release threshold. When ACC is driven
low, the accelerators are disabled.
For lightly loaded buses, having the accelerators active
may cause ringing or noise on the rising edge transition.
Disabling the accelerators will have the buffers continue
CC
) on both sides of the buffer is crossed. Once
September 30, 2010
FN7560.2
CC1
to