MAX1785EUU+T Maxim Integrated, MAX1785EUU+T Datasheet - Page 15

• Manufacturer Part Number: MAX1785EUU+T
• Description: Battery Management Smart Battery-Pack Controller
• Manufacturer: Maxim Integrated
• Series: MAX1785r

Figure 18’s high-frequency harmonic components are
much lower in amplitude, compared with Figure 17’s,
and the potential for EMI is significantly reduced. Figure
19 shows the same signal displayed for a MAX3060E
transmitting under the same conditions. Figure 19’s
high-frequency harmonic components are even lower.
In general, a transmitter’s rise time relates directly to the
length of an unterminated stub, which can be driven with
only minor waveform reflections. The following equation
expresses this relationship conservatively:
where t
For example, the MAX3060E’s rise time is typically
1850ns, which results in excellent waveforms with a stub
length up to 123ft. A system can work well with longer
unterminated stubs, even with severe reflections, if the
waveform settles out before the UART samples them.
Low-power shutdown mode is initiated by bringing both
RE high and DE low. In shutdown, the devices typically
draw only 1nA of supply current.
RE and DE can be driven simultaneously. The parts are
guaranteed not to enter shutdown if RE is high and DE is
low for less than 50ns. If the inputs are in this state for at
least 600ns, the parts are guaranteed to enter shutdown.
Enable times t_
acteristics tables assume the part was not in a low-
power shutdown state. Enable times t_
t_
drivers and receivers longer to become enabled from
low-power shutdown mode (t_
than from driver/receiver-disable mode (t_
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus con-
tention. The first, a foldback current limit on the output
stage, provides protection after a 20µs delay against
short circuits over the whole common-mode voltage
range (see Typical Operating Characteristics). The sec-
ond, a thermal shutdown circuit, forces the driver out-
puts into a high-impedance state if the die temperature
becomes excessive.
±15kV ESD-Protected, Fail-Safe, 20Mbps, Slew-Rate-
ZL(SHDN)
Limited RS-485/RS-422 Transceivers in a SOT
RISE
assume the parts were shut down. It takes
is the transmitter’s rise time.
Length = t
ZH
______________________________________________________________________________________
Low-Power Shutdown Mode
and t_
RISE
Driver Output Protection
ZL
/ (10 x 1.5ns/ft)
in the Switching Char-
ZH(SHDN)
ZH(SHDN)
ZH
, t_
, t_
ZL(SHDN)
ZL
).
and
)
Figure 17. Driver Output Waveform and FFT Plot of MAX3062E
Transmitting a 25kHz Signal
Figure 18. Driver Output Waveform and FFT Plot of MAX3061E
Transmitting a 25kHz Signal
Figure 19. Driver Output Waveform and FFT Plot of MAX3060E
Transmitting a 25kHz Signal
0
0
0
125kHz/div
125kHz/div
125kHz/div
1.25MHz
1.25MHz
1.25MHz
20dB/div
20dB/div
20dB/div
15