MAX14871_14 Datasheet, PDF (11/15 Pages) Maxim Integrated Products – 4.5V to 36V Full-Bridge DC Motor Driver

MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Slope Control
The MAX14871 drivers turn-on and turn-off with active
slope control during the M1/M2 transition times. This
integrated slew rate limiting reduces EMC, like conducted
and radiated EMI, associated with high di/dt and dv/dt
rates.
Thermal Shutdown
The MAX14871 includes integrated protection against
thermal overload. When the junction temperature exceeds
160°C (typ), the H-bridge is tri-stated and FAULT asserted.
M1 and M2 are automatically re-enabled when the
junction temperature falls to 150°C (typ).
Current Sensing
Connect a sense resistor (RSENSE) between COM and
GND to monitor the motor current during operation. Select
RSENSE such that the voltage at COM created by motor
current flowing through the sense resistor is limited to with-
in 250mV relative to GND (-250mV ≤ V_COM ≤ +250mV).
Table 1. Current Regulation Modes
INPUTS
MODE
0.75V
0.75V
GND
> 1.5V
GND
> 1.5V
VREF
GND
> 0.4V
GND
GND
> 0.4V
> 0.4V
Regulation Mode
25% Ripple
25% Ripple
TCOFF
TCOFF
TCOFF
TCOFF
Minimize series trace resistance from RSENSE to GND to
minimize voltage sense errors due to parasitic trace inter-
connect resistance. Use a star ground connection between
the MAX14871 GND pins and the GND-side of RSENSE.
Connect the SNS trace close to the R_SENSE resistor in
order to minimize current-sensing error introduced by IR
voltage created by the trace resistance of the high-current
COM to R_SENSE trace. If external current monitoring/
regulation is used, as shown in Figure 5, connect the
voltage sense inputs close to the R_SENSE resistor. Optionally
use differential voltage sensing for higher accuracy
sensing. Connect the voltage sense close to the RSENSE
resistor and/or use differential voltage-sensing. See Figure 4.
Current Regulation
The MAX14871 features internal current-regulation to limit
the stall current. Current regulation is based on the maxi-
mum motor current (set with the RSENSE resistor) and
the voltage at VREF. When the motor current exceeds the
value, the motor current is automatically reduced, either
by driving both H-bridge outputs low (braking/slow decay),
CURRENT REGULATION MODE
Decay Type
VREF
FAST
Internal (=1V)
FAST
External
FAST
Internal (=1V)
SLOW
Internal (=1V)
FAST
External
SLOW
External
TCOFF
-
-
15µs
15µs
Toff
Toff
M1
COM
GND
GN^EP D
GND
GND
GND
GND
COM
M2
Figure 4. Star connection between COM, SNS, and GND
To SNS
R_SENSE
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