MAX1785EUU+T Maxim Integrated, MAX1785EUU+T Datasheet - Page 11

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

The MAX3060E/MAX3061E/MAX3062E high-speed trans-
ceivers for RS-485/RS-422 communication contain one
driver and one receiver. These devices feature fail-safe
circuitry, which guarantees a logic-high receiver output
when the receiver inputs are open or shorted, or when
they are connected to a terminated transmission line with
all drivers disabled (see the Fail Safe section). All devices
have a hot-swap input structure that prevents distur-
bances on the differential signal lines when a circuit
board is plugged into a hot backplane (see the Hot-Swap
Capability section). The MAX3060E features a reduced
slew-rate driver that minimizes EMI and reduces reflec-
tions caused by improperly terminated cables, allowing
error-free data transmission up to 115kbps (see the
Reduced EMI and Reflections section). The MAX3061E is
also slew-rate limited, transmitting up to 500kbps. The
MAX3062E driver is not slew-rate limited, allowing trans-
mit speeds up to 20Mbps. The MAX3060E/MAX3061E/
MAX3062E are half-duplex transceivers.
All of these parts operate from a single +5V supply.
Drivers are output short-circuit current limited. Thermal-
shutdown circuitry protects drivers against excessive
power dissipation. When activated, the thermal-shut-
down circuitry places the driver outputs into a high-
impedance state.
±15kV ESD-Protected, Fail-Safe, 20Mbps, Slew-Rate-
PIN
1
2
3
4
5
6
7
8
Limited RS-485/RS-422 Transceivers in a SOT
NAME
GND
V
RO
DE
RE
DI
A
B
CC
______________________________________________________________________________________
Detailed Description
Receiver Output. When RE is low and when A - B ≥ -50mV, RO is high; if A - B ≤ -200mV, RO is low. RO
is high impedance when RE is high.
Receiver Output Enable. Drive RE low to enable RO; RO is high impedance when RE is high. Drive RE
high and DE low to enter low-power shutdown mode. RE is a hot-swap input and reverts to a standard
CMOS input after the first low transition.
Driver Output Enable. Drive DE high to enable driver outputs. Driver outputs are high impedance when
DE is low. Drive RE high and DE low to enter low-power shutdown mode. DE is a hot-swap input and
reverts to a standard CMOS input after the first high transition.
Driver Input. With DE high, a low on DI forces the noninverting output low and the inverting output high.
Similarly, a high on DI forces the noninverting output high and the inverting output low.
Ground
Noninverting Receiver Input and Noninverting Driver Output
Inverting Receiver Input and Inverting Driver Output
Positive Supply. Bypass with a 0.1µF capacitor to GND.
The receivers of the MAX3060E and MAX3061E incorpo-
rate input filtering in addition to input hysteresis. This fil-
tering enhances noise immunity with differential signals
that have very slow rise and fall times. Receiver propa-
gation delay increases by 2ns due to this filtering.
The MAX3060E family of devices guarantee a logic-high
receiver output when the receiver inputs are shorted or
open, or when they are connected to a terminated trans-
mission line with all drivers disabled. This is done by set-
ting the receiver threshold between -50mV and
-200mV. If the differential receiver input voltage (A - B) is
greater than or equal to -50mV, RO is logic high. If
A - B is less than or equal to -200mV, RO is logic low. In
the case of a terminated bus with all transmitters dis-
abled, the receiver’s differential input voltage is pulled to
0V by the termination. In the case of an unterminated bus
with all transmitters disabled, the receiver’s differential
input voltage is pulled to 0V by the receiver’s input resis-
tors. With the receiver thresholds of the MAX3060E fami-
ly, this results in a logic high output with a 50mV
minimum input noise margin. Unlike previous fail-safe
devices, the -50mV to -200mV threshold complies with
the ±200mV EIA/TIA-485 standard.
FUNCTION
Receiver Input Filtering
Pin Description
Fail-Safe
11