Maxim MAX14871 4.5v to 36v full-bridge dc motor driver Datasheet

EVALUATION KIT AVAILABLE
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
General Description
Benefits and Features
The MAX14871 DC motor driver provides a low-power
and simple solution for driving and controlling brushed
motors with voltages between 4.5V and 36V. Very low
driver on resistance reduces power during dissipation.
●● Drive More Power and Reduce Footprint
• Up to 2.8A Peak Motor-Current Package
• Flexible 4.5V–36V Supply Enables Longer Runtime
●● Low Power Consumption Runs Cooler and Longer
• 334mΩ (typ) Total Bridge On-Resistance
• 1mA (typ) Supply Current at 30kHz/24V
• 10µA (max) Standby Current at 12V
The MAX14871 features a charge-pump-less design for
reduced external components and low supply current.
Integrated current regulation allows user-defined peak startup
motor currents and requires minimal external components.
●● Simplified Designs Reduces Time to Market
• Charge-Pump-Less Architecture
• Current Regulation Only Requires a Sense Resistor
• Current-Sense Input Simplifies PCB Layout
• Internal/External VREF for Current Regulation
• Fast/Slow/25% Ripple Current Regulation Modes
The MAX14871 includes 3 modes of current regulation:
fast decay, slow decay, and 25% current ripple modes.
Current regulation based on 25% ripple simplifies the
design and enables regulation independent of motor
characteristics. A separate voltage sense input (SNS) reduces current-sensing errors due to parasitic trace resistance.
●● Integrated Protection Provides Robust Driving Solutions
• Short-Circuit-Protected Drivers
• Thermal Shutdown Undervoltage Lockout
• Diagnostic FAULT Output
• -40°C to +85°C Temperature Range
The MAX14871 features shoot-through protection and
internal free-wheeling diodes that absorb inductive motor
currents. Driver outputs are short-circuit-protected from
shorts to ground, to the supply, and between M1 and M2.
An active-low FAULT output signals thermal overload and
overcurrents during fault conditions.
The MAX14871 is available in a 16-pin TSSOP-EP package
and operates over the -40°C to +85°C temperature range.
Ordering Information appears at end of data sheet.
Applications
●● Printers and Scanners
●● Industrial Automation
●● Vending and Gaming Machines
Typical Application Circuit
24V
M
M1
VDD
3.3V
M2
3.3V
MAX14871
FAULT
IRQ
µC
VDD
DIR
GPO
VDD
PWM
PWM
EN
DRIVER
3.3V
DRIVER
VREF
TCOFF
CURRENT
REGULATION
COFF
MODE
SNS
GND
COM
RSENSE
19-7063; Rev 0; 9/14
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Absolute Maximum Ratings
(All voltages referenced to GND)
VDD.........................................................................-0.3V to +40V
M1, M2........................................................ -0.3V to (VDD+0.3V)
PWM, DIR, FAULT, EN, SNS, VREF,
MODE, TCOFF................................................................ -0.3V to +6.0V
COM......................................................................-0.3V to +0.3V
Current Into M1, M2 ..............................................................±3A
Continuous Power Dissipation (TA = +70°C)
Single-Layer Board (derate at 21.3mW/°C
above +70°C).............................................................1702mW
Multiple-Layer Board (derate at 26.1mW/°C
above +70°C).............................................................2088mW
Operating Temperature Range............................ -40°C to +85°C
Junction Temperature....................................................... +150ºC
Storage Temperature Range..............................-65ºC to +150°C
Lead Temperature (Soldering, 10s) ................................. +300°C
Solder Temperature (Reflow) ..........................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Package Thermal Characteristics (Note 1)
Junction-to-Case Thermal Resistance (θJC)
TSSOP-EP (Single-Layer Board)...................................3°C/W
TSSOP-EP (Multiple-Layer Board).................................3°C/W
Junction-to-Ambient Thermal Resistance (θJA)
TSSOP-EP (Single-Layer Board).................................47°C/W
TSSOP-EP (Multiple-Layer Board)............................38.3°C/W
Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Electrical Characteristics
(VDD = 4.5V to 36V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VDD = 12V, TA = +25°C)(Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
36
V
POWER SUPPLY
Supply Voltage
VDD
4.5
Supply Current
IDD
EN = low, M1/M2
not connected
fPWM = 50kHz
No switching
0.5
1.2
Shutdown Supply Current
ISHDN
EN = high, Driver
is in shutdown
VDD = 12V
3.7
10
VDD = 36V
10
20
Undervoltage Lockout
Threshold
VUVLO
VDD rising
3.8
4.3
Undervoltage Lockout
Threshold Hysteresis
VUVLO_HYST
1
3.3
400
mA
μA
V
mV
DRIVER (M1, M2)
Driver Output Resistance
(High-Side + Low-Side)
Driver Overload Current Limit
M1, M2 Leakage Current
M1, M2 Body Diode ForwardVoltage
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RON
IM_ = 2.8A
TJ = 25°C
334
435
TJ = 125°C
465
620
IM_OL
IM_LKG
VBF
3
EN = High, VM1 = VM2 = 0V or VDD
-1
mΩ
A
+1
Low-side diode, EN = High, IF = 2.8A
1.5
High-side diode, EN = High, IF = 2.8A
1.5
μA
V
Maxim Integrated │ 2
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Electrical Characteristics (continued)
(VDD = 4.5V to 36V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VDD = 12V, TA = +25°C)(Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CURRENT REGULATION (VREF, SNS, COM, TCOFF, MODE)
Fixed Off-Time, Fast Decay Current
Regulation
MODE Select Threshold
MODE Internal Pulldown
Resistance
VREF Internal/External Select
Threshold
VREF Voltage Range for External VREF Current Regulation
VREF Input Leakage
SNS Threshold for Internal
VVREF Current Regulation
SNS Threshold for External
VVREF Current Regulation
Current-Sense Amplifier Gain
VMODE_TH
RMODE_PD
0.2
25% Ripple Current Regulation
Fixed Off-Time, Slow Decay Current
Regulation
0.5
VMODE = 5V
0.6
VVREF_TH
1
V
2.2
MΩ
0.4
V
1.5
1
0.2
VDD ≥ 5V
0.5
2
VDD < 5V
0.5
1.3
IVREF_LKG
VREF = 2V
-1
+1
VSNS_IVR_
VSNS rising, VVREF < VVREF_TH, All
current regulation modes
94
100
110
VSNS_IVR_THF
VSNS falling, 25% Ripple Mode,
VVREF < VVREF_TH
-82
-75
-69
VSNS_ER_THR
VSNS rising, VVREF > VVREF_TH,
All current regulation modes
VSNS_ER_THF
VSNS falling, 25% Ripple Mode,
VVREF > VVREF_TH
VVREF
/ AV
0.75 x
VVREF
/AV
10
VVREF
THR
AV
V
μA
mV
V
VVREF = 1V (Note 4)
9.6
10.5
V/V
SNS Input Leakage Current
ISNS_LKG
VSNS = ±250mV
-1
+1
μA
COM Leakage Current
ICOM_LKG
EN = High, VCOM = ±250mV
-1
+1
μA
TCOFF Current
ITCOFF
TCOFF is connected to GND
TCOFF Threshold
VTCOFF
LOGIC SIGNALS (PWM, DIR, EN, FAULT)
Input Logic-High Voltage
VIH
PWM, DIR
Input Logic-Low Voltage
VIL
PWM, DIR
EN Input Logic-High Voltage
VEN_IH
EN Input Logic-Low Voltage
VEN_IL
Input Leakage Current
IIL
6
10
15
μA
0.92
1
1.08
V
2
V
0.8
1.6
PWM, DIR, EN, VINPUT = 5.5V or 0V
FAULT Output Low Voltage
VOL
FAULT Off Leakage Current
IF_LKG
FAULT deasserted, VFAULT = 5.5V
Thermal-Shutdown Threshold
TSHDN
Temperature rising, FAULT asserted
Thermal-Shutdown Hysteresis
TSHDN_HYST
V
V
-1
FAULT asserted, ISINK = 5mA
-1
0.4
V
+1
μA
0.5
V
+1
μA
PROTECTION
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+160
°C
10
°C
Maxim Integrated │ 3
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
AC Electrical Characteristics
(VDD = 4.5V to 36V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VDD = 12V, TA = +25°C)(Note 3)
PARAMETER
PWM Frequency
Dead Time
SYMBOL
fSW
CONDITIONS
MIN
TYP
EN = Low, Switching signal applied
at PWM
MAX
UNITS
50
kHz
tDEAD
140
ns
M1, M2 Slew Rate
SR
200
V/μs
M1, M2 High-Side Propagation
Delay
tPR
RL = 1kΩ, CL = 50pF, PWM/DIR rising, Figure 1
620
ns
M1, M2 Low-Side Propagation
Delay
tPF
RL = 1kΩ, CL = 50pF, PWM/DIR falling, Figure 1
583
ns
Fixed Off-Time with Internal
VREF Current Regulation
tOFF_D
PWM = High, EN = Low, VSNS >
VSNS_IVR_THR, VVREF < VVREF_
TH, TCOFF unconnected
Current Regulation Minimum
On-Time
tCR_BL
PWM = High, EN = Low, VSNS >
VSNS_IR_THR or VSNS_ER_THF
2.5
μs
Overcurrent Blanking Time
tOC_BL
M1/M2 is shorted to VDD or GND,
Figure 2
1
μs
Overcurrent Autoretry Timeout
tOC_TO
PWM = High, EN = Low, IM or IM2 >
IM_OL, Figure 2
2
ms
Enable Turn-on Delay
tEN_ON
PWM = High, RL = 1kΩ, CL = 50pF,
EN falling, M1/M2 rising to 10%,
Figure 3
23
μs
Enable Turn-off Delay
tEN_OFF
PWM = High, RL = 1kΩ, CL = 50pF,
EN rising, M1/M2 falling to 90%,
Figure 3
50
μs
7.8
15
22
μs
Note 2: All units are production tested at TA = +25°C. Specifications over temperature are guaranteed by design.
Note 3: AV is the fixed voltage gain of the internal current sense amplifier. It is the factor by which the VSNS voltage is multiplied for
comparison with the external VREF voltage when using external VREF current regulation. See the Applications Information
section for more information.
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Maxim Integrated │ 4
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Test Circuits/Timing Diagrams
M1/ M2
RL
CL
VL
PWM/DIR
0V
1V
M1/M2
1V
tPR
VDD
0V
tPF
Figure 1. M1/M2 Propagation Delays
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Maxim Integrated │ 5
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Test Circuits/Timing Diagrams (continued)
IM1 or IM2
IM_OL
0A
tOC_BL
VL
FAULT
0V
tOC_TO
Figure 2. Overcurrent Autoretry Timeout
M1/ M2
RL
EN
CL
VL
1.5V
1.5V
tEN_ON
0V
tEN_OFF
90%
M1/M2
10%
VDD
0V
Figure 3. Enable/Disable Delays
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Maxim Integrated │ 6
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Typical Operating Characteristics
(VDD = 24V, TA = +25°C, unless otherwise noted.)
HIGH-SIDE ON RESISTANCE
vs. LOAD CURRENT
0.30
VDD = 36V
0.10
VDD = 4.5V
VDD = 36V
0.15
0.06
0.10
1000
2000
0.00
3000
0
1000
toc04
1.4
6
toc05
4
VDD = 4.5V
VDD = 24V
1.0
0.8
0
15
30
45
60
75
0.0
90
VDD = 5V
5
10
TEMPERATURE (oC)
15
20
25
30
35
HIGH-SIDE M1/M2 BODY DIODE
FORWARD-VOLTAGE vs. LOAD
105
130
toc06
TA = -40°C
TA = 25°C
TA = 85°C
40
45
0.0
50
0
1
2
3
LOAD CURRENT (A)
OFF-TIME vs COFF CAPACITANCE
toc07
toc08
55
50
1.0
45
40
TA = 25°C
0.6
tOFF (µs)
0.8
VBF (V)
0.6
DATA RATE (kHz)
1.2
80
0.2
CL = 10pF on M1/M2
0
55
0.4
VDD = 12V
0.2
30
0.8
0.4
2
-15
5
1.0
0.6
-30
-20
LOW-SIDE M1/M2 BODY DIODE
FORWARD-VOLTAGE vs. LOAD
1.2
VBF (V)
ICC (mA)
VDD = 24V
-45
-45
TEMPERATURE (oC)
VDD = 36V
1.2
ISHDN (µA)
0.00
3000
SUPPLY CURRENT
vs. SWITCHING RATE
1.6
VDD = 36V
8
2000
LOAD CURRENT (mA)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
12
LOW-SIDE
0.05
LOAD CURRENT (mA)
0
0.20
0.08
0.02
0
HIGH-SIDE
0.25
0.12
0.10
toc03
ILOAD = 1A
0.30
0.14
0.04
0.05
ON-RESISTANCE
vs. TEMPERATURE
0.40
ON-RESISTANCE (Ω)
ON-RESISTANCE (Ω)
0.15
10
toc02
0.35
0.16
VDD = 4.5V
0.20
0.00
LOW-SIDE ON RESISTANCE
vs. LOAD CURRENT
0.20
0.18
0.25
ON-RESISTANCE (Ω)
toc01
TA = 85°C
TA = -40°C
35
30
25
0.4
20
0.2
10
15
5
0.0
0
1
2
LOAD CURRENT (A)
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3
0
100
150
200
250
300
350
400
450
500
COFF (pF)
Maxim Integrated │ 7
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Pin Configuration
TOP VIEW
+
COM
1
16 COM
M1
2
M1
3
VDD
4
SNS
5
12 VREF
PWM
6
11 EN
DIR
7
10 FAULT
MODE
8
9
*EP
15 M2
14 M2
MAX14871
13 VDD
TCOFF
TSSOP-EP
* EP = Exposed Pad. Connect to ground plane.
Pin Description
PIN
NAME
FUNCTION
COM Current Output. Connect a sense resistor, RSENSE, from COM to GND to use internal current
regulation and/or external current control. Connect both COM pins together.
1, 16
COM
2, 3
M1
Motor Driver Output 1. See the Function Tables for more information. Connect both M1 pins together.
4, 13
VDD
Power Supply Input. Bypass VDD to GND with a 1μF ceramic capacitor as close to the device as
possible. Connect both VDD pins together.
5
SNS
Current Sense Input. Connect SNS to COM to enable current regulation. To bypass current regulation,
connect SNS to GND.
6
PWM
PWM Control Logic Input. PWM and DIR control M1 and M2. See the Function Tables for more
information.
7
DIR
8
MODE
Current Regulation Mode Select Input. Connect MODE to GND for fast decay regulation. Connect
VMODE > 1.5V for slow decay current regulation. Connect 0.5V ≤ VMODE ≤ 1V for fast decay with 25%
ripple. MODE has a 1MΩ internal pull-down resistor.
TCOFF
Current Regulation Timing Control. For external VREF-based current regulation, connect a capacitor
to TCOFF to set the off-time (tOFF). For internal VREF-based current regulation leave TCOFF unconnected when using internal VREF-based current regulation. See the Current Regulation section for more
information.
9
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Direction Control Logic Input. PWM and DIR control M1 and M2. See the Function Tables for more
information.
Maxim Integrated │ 8
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Pin Description (continued)
PIN
NAME
10
FAULT
11
EN
EP
GND
14, 15
M2
12
VREF
-
EP
FUNCTION
Open-Drain Active-Low Fault Output. FAULT goes low during an overcurrent condition and thermal
shutdown.
Active-Low Enable Input. Drive EN low to enable the driver outputs. Drive EN high to tri-state the driver
outputs.
Ground
Motor Driver Output 2. See the Function Tables for more information. Connect both M2 pins together.
Reference Voltage Input. The voltage applied to VVREF sets the maximum motor current during external
VVREF-based current regulation. Set VVREF<VREF_TH for internal VVREF-based current regulation.
See the Function Tables and the Current Regulation section for more information.
Exposed Pad. Connect to ground.
Function Table
PWM/DIR Control Logic
EN
INPUTS
OUTPUTS
OPERATING MODE
PWM
DIR
M1
M2
1
X
X
High-Impedance
High-Impedance
0
0
X
GND
GND
Brake
0
1
0
GND
VDD
Counter-Clockwise/Reverse
0
X = Don’t care
1
1
VDD
GND
Clockwise/Forward
Shutdown
Current Regulation Logic
INPUTS
OPERATING MODE (SEE TABLE 1)
EN
VREF
MODE
VSNS
0
< 0.2V
X
< 0.1V
Normal PWM Operation. No current regulation.
0
< 0.2V
VMODE < 0.5V
> 0.1V
Current regulation based on 15μs (typ) fixed off-time control
with fast decay using internal VREF.
0
< 0.2V
0.5V < VMODE < 1V
> 0.1V
Current regulation based on 25% current ripple fast decay
using internal VREF.
0
< 0.2V
VMODE > 1.5V
> 0.1V
Current regulation based on 15μs (typ) fixed off-time control
with slow decay using internal VREF.
0
> 0.4V
X
< VVREF/10
Normal PWM Operation. No current regulation.
0
> 0.4V
VMODE < 0.5V
> VVREF/10
Current regulation based on fixed TOFF-time control with fast
decay using external VREF.
0
> 0.4V
0.5V < VMODE < 1V
> VVREF/10
Current regulation based on 25% current ripple fast decay
using external VREF.
0
> 0.4V
VMODE > 1.5V
> VVREF/10
Current regulation based on fixed TOFF-time control with
slow decay using external VREF.
X = Don’t care
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Maxim Integrated │ 9
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Functional Diagram
M1
VDD
M2
MAX14871
VDD
EN
PWM
VDD
DRIVER
DIR
FAULT
DRIVER
MODE
VREF
CURRENT
REGULATION
TCOFF
SNS
COM
GND
RSENSE
Detailed Description
The MAX14871 DC brushed motor driver provides a
low-power and flexible solution for driving and controlling
brushed motors with voltages between 4.5V and 36V.
Peak motor currents of up to 2.8A ensure for large motor
torque that is controllable by an external PWM signal and/
or by autonomous internal current regulation.
M1 or M2 for longer than 1µs, an overcurrent condition
is detected and the H-bridge drivers are automatically
disabled and the FAULT output asserts.
Charge-pump-less design ensures for minimal external
components and low supply current.
If the overcurrent condition continues for longer than the
overcurrent autoretry timeout (2ms (typ)) the MAX14871
enters autoretry mode. In autoretry mode, the M1 and M2
outputs are re-enabled for 1µs (typ) and FAULT goes high
impedance. The drivers are disabled again and FAULT is
re-asserted if the overcurrent condition persists.
Integrated current regulation allows limiting peak startup
motor currents. Shoot-through protection with a 140ns
(typ) dead time ensures low operating current. Internal
free-wheeling diodes absorb inductive motor currents. The
FAULT output signals thermal overload and overcurrents.
PWM Control
The PWM input is used for motor speed/torque control.
Increasing or decreasing the duty cycle at PWM sets the
effective (average) voltage across the motor terminals
and allows first-order speed control.
Overcurrent Protection
When PWM is logic-high, the motor is driven in the
direction defined by DIR. When PWM is logic low, the
bridge is in brake mode. In brake mode, the motor current
continues flowing and recirculates through the low-side
transistors of the H-bridge driver, due to its inductive
impedance and back EMF.
The MAX14871 is protected against shorts on M1/M2 to
any voltages between VDD and GND, including shorts
to GND, VDD and between M1 and M2 via overcurrent
limiting. When a current above 6A (typ) flows through
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Maxim Integrated │ 10
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 within 250mV relative to GND (-250mV ≤ VCOM ≤ +250mV).
Minimize series trace resistance from RSENSE to GND to
minimize voltage sense errors due to parasitic trace interconnect resistance. Use a star ground connection between
the MAX14871 GND pins and the GND-side of RSENSE.
Connect the SNS trace close to the RSENSE resistor in
order to minimize current-sensing error introduced by IR
voltage created by the trace resistance of the high-current
COM to RSENSE trace. If external current monitoring/
regulation is used, as shown in Figure 5, connect the
voltage sense inputs close to the RSENSE 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 maximum 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),
Table 1. Current Regulation Modes
INPUTS
CURRENT REGULATION MODE
MODE
VREF
Regulation Mode
Decay Type
0.75V
GND
25% Ripple
FAST
Internal (=1V)
0.75V
> 0.4V
25% Ripple
FAST
External
GND
GND
TCOFF
FAST
Internal (=1V)
15µs
> 1.5V
GND
TCOFF
SLOW
Internal (=1V)
15µs
GND
> 0.4V
TCOFF
FAST
External
Toff
> 1.5V
> 0.4V
TCOFF
SLOW
External
Toff
COM
-
RSENSE
GND
EP
TCOFF
To SNS
M1
GND
VREF
GND
GND
GND
GND
COM
M2
Figure 4. Star connection between COM, SNS, and GND
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Maxim Integrated │ 11
MAX14871
or by reversing the H-bridge direction (fast decay). The
H-bridge is turned back to normal polarity after a defined
delay time (TOFF mode) or after the motor current has
reduced by 25% (25% ripple mode). See Table 1. The
MAX14871 Function Tables show how to set the regulation mode.
Regulation Modes
The MAX14871 offers two internal current regulation
modes: Constant off-time (TOFF) and 25% current ripple
regulation. For both modes, regulation is set when the
motor current (IM) exceeds the current limit defined by the
VREF voltage and the sense resistor:
IM_MAX = VVREF/(AV x RSENSE)
VREF
Either the internal VVREF voltage or an external voltage
on VREF can be used for current regulation. Select internal VREF-based regulation by setting VVREF < VREF_TH.
The internal VVREF is 1V (typ).
When an external voltage is used, the range of VREF is
defined by VVREF.
Fixed Off-Time (TOFF-time) Regulation
Fixed off-time regulation turns the H-bridge driver off for
a fixed time (tOFF time), as defined by the value of the
COFF capacitor connected between TCOFF and GND:
tOFF (µs)= COFF(pF)/10.
If VVREF < VVREF_TH and TCOFF is left unconnected,
then tOFF is 15µs (typ).
During the fixed TOFF-time regulation, the H-bridge can
operate in either slow or fast decay mode. See Table 1.
Slow Decay Mode
Slow decay, also called brake mode, is selected by setting VMODE > 1.5V. In slow decay, both H-bridge low-side
drivers are turned on so that the inductive motor
current recirculates through the low-side transistors and
the motor’s terminals see a differential voltage near
zero (VDIFF = 2 x IM x RON_LS). During the slow-decay
TOFF period (tOFF) motor current does not flow through
the external VDD/GND supply and the voltage across
RSENSE is zero. The current decay during tOFF is a
first-order exponential decay with a time constant equal
to the motor’s electrical time constant (L/R). The rate of
current decay during tOFF is proportional to the motor’s
back EMF/rotational speed.
4.5V to 36V Full-Bridge DC Motor Driver
Fast Decay Mode
Fast decay mode can be used as an alternative to slow
decay during fixed off-time regulation. Fast decay is
enabled by setting VMODE < 0.2V. In fast decay, the
H-bridge polarity is reversed during the tOFF period,
which results in faster motor current decay, since –VDD
is applied across the motor’s terminals. The motor
current decrease is first order with an L/R time constant
and proportional to (VDD + VEMF).
Note that if tOFF is larger than the motor’s L/R electrical
time constant, the inductive current can reverse direction,
causing the motor not to start-up. If fixed off-time regulation with fast decay is used, select TOFF carefully, based
on the motor’s electrical characteristics.
During fast decay, the motor’s inductive current recirculates through the external VDD supply, which charges up
the VDD bypass capacitor. Thus the voltage seen across
RSENSE is negative during the tOFF delay.
25% Ripple Regulation
25% ripple regulation is based on the H-bridge switching
to fast decay period until the motor current falls by 25%.
When IM reaches the regulation limit, the bridge enters
fast decay until the IM falls to 75% of the current limit. The
H-bridge polarity is then turned back to normal drive. Thus
the motor current ramps up and down between 75% and
100% of the set-point current.
25% ripple regulation eliminates tOFF time tuning and the
TCOFF capacitor, allowing motors to be exchanged without
redesign.
Since 25% ripple regulation uses fast decay, the voltage
seen across RSENSE is negative during the time period
that the H-bridge polarity is reversed.
Select 25% ripple regulation mode by setting 0.5V <
VMODE < 1.0V. Leave TCOFF unconnected when 25%
ripple is used.
Applications Information
Layout Considerations
Connect duplicate pins (COM pins and VDD pins) together with low-resistance traces. See the Current Sensing
section for further layout recommendations.
Power Considerations
The MAX14871 driver can generate more power than the
package for the device can safely dissipate. Total power
dissipation for the device is calculated using the following
equation:
PTOTAL = PDRIVER + PSW + PD
www.maximintegrated.com
Maxim Integrated │ 12
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Operation with External Current Regulation
The power dissipated inside of the driver is calculated as:
PDRIVER = IM_LOAD2 x RON
The motor current can be controlled by external PWM
regulation using sense-resistor feedback in a control loop.
To disable the internal current regulation circuitry of the
MAX14871 and use external regulation, connect SNS
directly to ground. See Figure 5.
where IM_LOAD is the motor current and RON is the onresistance of the high and low-side FETs.
PSW is the power generated by the driver during the rise/
fall times in switching, and includes both arms of the bridge.
Calculate PSW using the following equation:
Note that, if fast decay control is used, the COM voltage
pulses negatively when the H-bridge direction is inverted.
PSW = IM_LOAD x 2 x VDS
= IM_LOAD x 2 x (1/2 x VDD x fSW x tR)
where IM_LOAD is the motor current, tR is the 200ns
(typ) rise or fall time of the driver output, and fSW is the
switching frequency.
The internal diodes dissipate power during switching, as
well. Calculate the power dissipated in the diodes as:
Use of External Capacitors
Maxim does not recommend using external capacitors
across the motor terminals. Added capacitance between
H-bridge outputs increases the power dissipated in the
H-bridge by:
PD = VDD2 x C x fSW
where C is the capacitance across M1/M2 and fSW is
the M1/M2 switching frequency. This power is dissipated
without good reason.
PD = IM_LOAD x 2 x VBF x tDEAD x fSW
Operation Without Internal Current Regulation
To operate the MAX14871 without internal or external
current regulation, connect SNS directly to GND. No
sense resistor is required for this configuration. See
Figure 4.
Note that conducted EMI on the VDD lines is also
worsened due to the high-capacitive current spikes.
9V
M
3.3V
M1
VDD
M2
3.3V
MAX14871
IRQ
FAULT
VDD
DIR
GPO
PWM
PWM
VDD
DRIVER
EN
DRIVER
µC
TCOFF
MODE
ADC
CURRENT
REGULATION
VREF
SNS
A
GND
COM
RSENSE
Figure 5. Operation with External Current Regulation
www.maximintegrated.com
Maxim Integrated │ 13
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Chip Information
Ordering Information
PART
MAX14871EUE+
TEMP RANGE
PIN-PACKAGE
-40°C to +85°C
16 TSSOP-EP
PROCESS: BiCMOS
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that
a “+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but the
drawing pertains to the package regardless of RoHS status.
www.maximintegrated.com
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
16 TSSOP-EP
U16E+3
21-0108
90-0120
Maxim Integrated │ 14
MAX14871
4.5V to 36V Full-Bridge DC Motor Driver
Revision History
REVISION
NUMBER
REVISION
DATE
0
9/14
DESCRIPTION
Initial release
PAGES
CHANGED
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For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2014 Maxim Integrated Products, Inc. │ 15