Datasheet

SATA I/II Bidirectional Redriver
with High ESD and Cable Detect
8
MAX4951AE
Detailed Description
The MAX4951AE consists of two identical buffers that
take SATA input signals and return them to full output
levels while withstanding ESD events up to Q8kV (HBM).
This device functions for SATA I/SATA II applications
Input/Output Terminations
Inputs and outputs are internally 50I terminated to V
CC
(see the Functional Diagram/Truth Table) and must be
AC-coupled to the SATA controller IC and SATA device
for proper operation.
OOB Logic
The MAX4951AE provides full OOB signal support
through high-speed amplitude detection circuitry. SATA
OOB differential input signals of 50mV
P-P
or less are
detected as off and not passed to the output. This pre-
vents the system from responding to unwanted noise.
SATA OOB differential input signals of 200mV
P-P
or
more are detected as on and passed to the output. This
allows OOB signals to transmit through the MAX4951AE.
The time for the amplitude detection circuit to detect an
inactive SATA OOB input and squelch the associated
output, or detect an active SATA OOB input and enable
the output, is less than 5ns (max).
Enable Input
The MAX4951AE features an active-high enable input
(EN). EN has an internal pulldown resistor of 330kI
(typ). When EN is driven low or left unconnected, the
MAX4951AE enters low-power standby mode and the
buffers are disabled, reducing supply current to 350FA
(typ). Drive EN high for normal operation.
Cable-Detect Input
The MAX4951AE features an active-low cable-detect
input (CAD). CAD has an internal pullup resistor of
330kI (typ). When CAD is driven high or left uncon-
nected, the MAX4951AE enters low-power standby
mode and the buffers are disabled, reducing supply
current to 350FA (typ). This signal is normally driven low
by inserting an eSATA cable into a properly wired socket
(see Figure 4). If the cable-detect feature is not desired,
simply ground this pin.
Output Boost Selection Inputs
The MAX4951AE has two digital control logic inputs, BA
and BB. BA and BB have internal pulldown resistors of
330kI (typ). BA and BB control the boost level of their
corresponding buffers (see the Functional Diagram/
Truth Table). Drive BA or BB low or leave unconnected
for standard SATA output levels. Drive BA or BB high to
boost the output. The boosted output level compensates
for attenuation from longer trace-length cables or to meet
eSATA specifications.
ESD Protection
As with all Maxim devices, ESD-protection structures are
incorporated on all pins to protect against electrostatic
discharges encountered during handling and assembly.
The MAX4951AE is protected against ESD up to Q8kV
(Human Body Model) without damage. The ESD struc-
tures withstand Q8kV in all states: normal operation and
powered down. After an ESD event, the MAX4951AE
continues to function without latchup.
Human Body Model
The MAX4951AE is characterized for Q8kV ESD pro-
tection using the Human Body Model (MIL-STD-883,
Method 3015). Figure 2 shows the Human Body Model
and Figure 3 shows the current waveform it generates
when discharged into a low impedance. This model con-
sists of a 100pF capacitor charged to the ESD voltage of
interest that is then discharged into the device through
a 1.5kI resistor.
Figure 2. Human Body ESD Test Model Figure 3. Human Body Current Waveform
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
C
S
100pF
R
C
1MΩ
R
D
1500Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
I
P
100%
90%
36.8%
t
RL
TIME
t
DL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
I
r
10%
0
0
AMPS