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DRV8821
SLVS912J – JANUARY 2009 – REVISED JANUARY 2016
DRV8821 Dual Stepper Motor Controller and Driver
1 Features
3 Description
•
The DRV8821 provides a dual microstepping-capable
stepper motor controller/driver solution for printers,
scanners, and other office automation equipment
applications.
1
•
•
•
•
•
•
Dual PWM Microstepping Motor Driver
– Built-In Microstepping Indexers
– Up to 1.5-A Current Per Winding
– Three-Bit Winding Current Control Allows up to
Eight Current Levels
– Low MOSFET On-Resistance
– Selectable Slow or Mixed Decay Modes
8-V to 32-V Operating Supply Voltage Range
Internal Charge Pump for Gate Drive
Built-in 3.3-V Reference
Simple Step/Direction Interface
Fully Protected Against Undervoltage,
Overtemperature, and Overcurrent
Thermally-Enhanced Surface Mount Package
2 Applications
•
•
•
•
•
•
Printers
Scanners
Office Automation Machines
Gaming Machines
Factory Automation
Robotics
Two independent stepper motor driver circuits include
four H-bridge drivers and microstepping-capable
indexer logic. Each of the motor driver blocks employ
N-channel power MOSFETs configured as an Hbridge to drive the motor windings.
A simple step/direction interface allows easy
interfacing to controller circuits. Pins allow
configuration of the motor in full-step, half-step,
quarter-step, or eighth step modes, and the selection
of slow or mixed decay modes.
Internal shutdown functions are provided for over
current
protection,
short-circuit
protection,
undervoltage lockout, and overtemperature.
The DRV8821 is packaged in a 48-pin HTSSOP
package (Eco-friendly : RoHS & no Sb/Br).
Device Information(1)
PART NUMBER
DRV8821
PACKAGE
HTSSOP (48)
BODY SIZE (NOM)
6.10 mm x 12.50 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Simplified Schematic
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
DRV8821
SLVS912J – JANUARY 2009 – REVISED JANUARY 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
4
4
5
5
5
6
6
7
Absolute Maximum Ratings .....................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Timing Requirements ................................................
Dissipation Ratings ...................................................
Typical Characteristics ..............................................
Detailed Description .............................................. 9
7.1 Overview ................................................................... 9
7.2 Functional Block Diagram ....................................... 10
7.3 Feature Description................................................. 10
7.4 Device Functional Modes........................................ 14
8
Application and Implementation ........................ 16
8.1 Application Information............................................ 16
8.2 Typical Application ................................................. 16
9
Power Supply Recommendations...................... 19
9.1 Bulk Capacitance .................................................... 19
10 Layout................................................................... 20
10.1 Layout Guidelines ................................................. 20
10.2 Layout Example .................................................... 21
10.3 Thermal Considerations ........................................ 22
11 Device and Documentation Support ................. 24
11.1
11.2
11.3
11.4
11.5
Documentation Support .......................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
24
24
24
24
24
12 Mechanical, Packaging, and Orderable
Information ........................................................... 24
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision I (January 2014) to Revision J
•
Added Pin Functions table, ESD Ratings table, Thermal Information table, Detailed Description section, Application
and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation
Support section, and Mechanical, Packaging, and Orderable Information section................................................................ 1
Changes from Revision H (August 2013) to Revision I
•
2
Page
Page
Changed typo in Overcurrent Protection section ................................................................................................................. 14
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5 Pin Configuration and Functions
DCA Package
48-Pin HTSSOP
Top View
VM
VM
AOUT2
AISEN
AOUT1
ABDECAY
CP1
CP2
VCP
PGND
PGND
Solder these
PGND
pins to copper
PGND
heatsink area
PGND
PGND
V3P3
ABVREF
CDVREF
CDDECAY
DOUT2
DISEN
DOUT1
VM
VM
1
48
2
3
47
46
4
45
5
6
44
43
7
8
42
41
9
40
10
11
39
38
12
13
37
36
14
15
35
34
16
17
33
32
18
19
20
31
30
29
21
28
27
22
23
24
26
25
BOUT1
BISEN
BOUT2
ABSTEP
ABUSM0
ABDIR
ABENBLn
ABUSM1
ABRESETn
PGND
PGND
Solder these
PGND
pins to copper
PGND
heatsink area
PGND
PGND
CDSTEP
CDUSM0
CDDIR
CDENBLn
CDUSM1
CDRESETn
COUT1
CISEN
COUT2
Pin Functions
PIN
I/O (1)
DESCRIPTION
1,2,
23, 24
—
Motor supply voltage (multiple pins)
Connect all VM pins together to motor supply voltage.
Bypass each VM to GND with a 0.1-µF, 35-V ceramic capacitor.
V3P3
16
—
3.3 V regulator output
Bypass to GND with 0.47-μF, 6.3-V ceramic capacitor.
GND
10-15,
34-39
—
Power ground (multiple pins)
Connect all PGND pins to GND and solder to copper heatsink areas.
CP1
7
IO
CP2
8
IO
Charge pump flying capacitor
Connect a 0.01-μF capacitor between CP1 and CP2
VCP
9
IO
Charge pump storage capacitor
Connect a 0.1-μF, 16 V ceramic capacitor to VM
ABSTEP
45
I
Motor AB step input
Rising edge causes the indexer to move one step.
ABDIR
43
I
Motor AB direction input
Level sets the direction of stepping.
ABUSM0
44
I
Motor AB microstep mode 0
ABUSM1
41
I
Motor AB microstep mode 1
USM0 and USM1 set the step mode - full step, half step, quarter
step, or eight microsteps/step.
ABENBLn
42
I
Motor AB enable input
Logic high to disable motor AB outputs, logic low to enable.
ABRESETn
40
I
Motor AB reset input
Active-low reset input initializes the indexer logic and disables the Hbridge outputs for motor AB.
ABDECAY
6
I
Motor AB decay mode
Logic low for slow decay mode, high for mixed decay.
ABVREF
17
I
Motor AB current set reference
voltage
Sets current trip threshold.
AOUT1
5
O
Bridge A output 1
AOUT2
3
O
Bridge A output 2
Connect to first coil of bipolar stepper motor AB, or DC motor
winding.
AISEN
4
—
Bridge A current sense
Connect to current sense resistor for bridge A.
NAME
NO.
EXTERNAL COMPONENTS OR CONNECTIONS
POWER AND GROUND
VM
(4 pins)
MOTOR AB
(1)
Directions: i = input, O = output, OZ = 3-state output, OD = open-drain ouput, IO = input/ouput
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Pin Functions (continued)
PIN
NAME
NO.
I/O (1)
DESCRIPTION
EXTERNAL COMPONENTS OR CONNECTIONS
BOUT1
48
O
Bridge B output 1
BOUT2
46
O
Bridge B output 2
Connect to second coil of bipolar stepper motor AB, or DC motor
winding.
BISEN
47
—
Bridge B current sense
Connect to current sense resistor for bridge B.
CDSTEP
33
I
Motor CD step input
Rising edge causes the indexer to move one step.
CDDIR
31
I
Motor CD direction input
Level sets the direction of stepping.
CDUSM0
32
I
Motor CD microstep mode 0
CDUSM1
29
I
Motor CD microstep mode 1
USM0 and USM1 set the step mode - full step, half step, quarter
step, or eight microsteps/step.
CDENBLn
30
I
Motor CD enable input
Logic high to disable motor CD outputs, logic low to enable.
CDRESETn
28
I
Motor CD reset input
Active-low reset input initializes the indexer logic and disables the Hbridge outputs for motor CD.
CDDECAY
19
I
Motor CD decay mode
Logic low for slow decay mode, high for mixed decay.
Sets current trip threshold.
MOTOR CD
CDREF
18
I
Motor CD current set reference
voltage
COUT1
27
O
Bridge C output 1
COUT2
25
O
Bridge C output 2
Connect to first coil of bipolar stepper motor CD, or DC motor
winding.
CISEN
26
—
Bridge C current sense
Connect to current sense resistor for bridge C.
DOUT1
22
O
Bridge D output 1
DOUT2
20
O
Bridge D output 2
Connect to second coil of bipolar stepper motor CD, or DC motor
winding.
DISEN
21
—
Bridge D current sense
Connect to current sense resistor for bridge D.
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
VM
(2)
MIN
MAX
UNIT
Power supply voltage
–0.3
34
V
(3)
–0.5
5.75
V
1.5
A
VI
Logic input voltage
IO(peak)
Peak motor drive output current, t < 1 μs
IO
Motor drive output current
PD
Continuous total power dissipation
See Dissipation Ratings
TJ
Operating virtual junction temperature
–40
150
°C
TA
Operating ambient temperature
–40
85
°C
Tstg
Storage temperature
–60
150
°C
(1)
(2)
(3)
(4)
Internally limited
(4)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltage values are with respect to network ground terminal.
Input pins may be driven in this voltage range regardless of presence or absence of VM.
Power dissipation and thermal limits must be observed.
6.2 ESD Ratings
VALUE
(1)
2000
Charged device model (CDM), per JEDEC specification JESD22-C101,
all pins (2)
1000
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins
V(ESD)
(1)
(2)
4
Electrostatic discharge
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
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6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN
VM
Motor power supply voltage
IMOT
Continuous motor drive output current (1)
VREF
VREF input voltage
(1)
NOM
MAX
32
V
1
1.5
A
4
V
8
1
UNIT
Power dissipation and thermal limits must be observed.
6.4 Thermal Information
DRV8821
THERMAL METRIC
(1)
DCA (HTSSOP)
UNIT
48 PINS
RθJA
Junction-to-ambient thermal resistance
31.3
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
16.3
°C/W
RθJB
Junction-to-board thermal resistance
15
°C/W
ψJT
Junction-to-top characterization parameter
0.6
°C/W
ψJB
Junction-to-board characterization parameter
14.9
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
0.6
°C/W
(1)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
6.5 Electrical Characteristics
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
5
8
mA
2.5
μA
8
V
POWER SUPPLIES
IVM
VM operating supply current
VM = 24 V, no loads
IVMSD
VM shutdown supply current
VM = 24 V, ABENBLn = CDENBLn = 1
VUVLO
VM undervoltage lockout voltage
VM rising
6.5
VCP
Charge pump voltage
Relative to VM
12
VV3P3
VV3P3 output voltage
3.20
3.30
V
3.40
V
0.7
V
LOGIC-LEVEL INPUTS
VIL
Input low voltage
VIH
Input high voltage
VHYS
Input hysteresis
IIN
Input current
(internal pulldown current)
2
0.3
V
0.45
VIN = 3.3 V
0.6
V
100
μA
OVERTEMPERATURE PROTECTION
tTSD
Thermal shutdown temperature
Die temperature
150
°C
MOTOR DRIVER
Rds(on)
Motor AB FET on resistance
(each individual FET)
VM = 24 V, IO = 0.8 A, TJ = 25°C
0.25
VM = 24 V, IO = 0.8 A, TJ = 85°C
0.31
Rds(on)
Motor CD FET on resistance
(each individual FET)
VM = 24 V, IO = 0.8 A, TJ = 25°C
0.30
VM = 24 V, IO = 0.8 A, TJ = 85°C
0.38
IOFF
Off-state leakage current
fPWM
Motor PWM frequency (1)
tBLANK
ITRIP blanking time (2)
tF
Output fall time
50
300
ns
tR
Output rise time
50
300
ns
(1)
(2)
45
50
0.37
0.45
Ω
Ω
±12
μA
55
kHz
μs
3.75
Factory option 100 kHz.
Factory options for 2.5 μs, 5 μs or 6.25 μs.
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Electrical Characteristics (continued)
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
3
4.5
IOCP
Overcurrent protect level
1.5
tOCP
Overcurrent protect trip time
2.5
tMD
Mixed decay percentage
Measured from beginning of PWM cycle
UNIT
A
μs
75%
VREF INPUT/CURRENT CONTROL ACCURACY
IREF
xVREF input current
ΔICHOP
xVREF = 3.3 V
Chopping current accuracy
–3
3
xVREF = 2.5 V, derived from V3P3;
71% to 100% current
–5%
5%
xVREF = 2.5 V, derived from V3P3;
20% to 56% current
–10%
10%
μA
6.6 Timing Requirements
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
UNIT
200
kHz
1
fSTEP
Step frequency
2
tWH(STEP)
Pulse duration, xSTEP high
2.5
μs
3
tWL(STEP)
Pulse duration, xSTEP low
2.5
μs
4
tSU(STEP)
Setup time, command to xSTEP rising
200
ns
5
tH(STEP)
Hold time, command to xSTEP rising
200
ns
6
tWAKE
Wakeup time, SLEEPn inactive to xSTEP
1
ms
6.7 Dissipation Ratings
RθJA
DERATING FACTOR
ABOVE TA = 25°C
TA < 25°C
TA = 70°C
TA = 85°C
Low-K (1)
75.7°C/W
13.2 mW/°C
1.65 W
1.06 W
0.86 W
Low-K (2)
32°C/W
31.3 mW/°C
3.91 W
2.50 W
2.03 W
30.3°C/W
33 mW/°C
4.13 W
2.48 W
2.15 W
22.3°C/W
44.8 mW/°C
5.61 W
3.59 W
2.91 W
BOARD
High-K (3)
High-K
(1)
(2)
(3)
(4)
(4)
PACKAGE
DCA
The JEDEC Low-K board used to derive this data was a 76-mm x 114-mm, 2-layer, 1.6-mm thick PCB with no backside copper.
The JEDEC Low-K board used to derive this data was a 76-mm x 114-mm, 2-layer, 1.6-mm thick PCB with 25-cm2 2-oz copper on back
side.
The JEDEC High-K board used to derive this data was a 76-mm x 114-mm, 4-layer, 1.6-mm thick PCB with no backside copper and
solid 1-oz internal ground plane.
The JEDEC High-K board used to derive this data was a 76-mm x 114-mm, 4-layer, 1.6-mm thick PCB with 25-cm2 1-oz copper on back
side and solid 1-oz internal ground plane.
1
2
3
xSTEP
xDIR, xUSMx
4
5
ABENBLn
& CDENBLn
6
Figure 1. Timing Diagram
6
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5.20
5.20
5.00
5.00
Supply Current (mA)
Supply Current (mA)
6.8 Typical Characteristics
4.80
4.60
4.40
4.20
8V
4.00
24 V
4.80
4.60
-40°C
4.40
0°C
4.20
25°C
4.00
70°C
27 V
85°C
3.80
3.80
-40°C
0°C
25°C
70°C
85°C
8V
Temperature (ƒC)
Figure 2. Supply Current over Temperature
27 V
C002
Figure 3. Supply Current over Supply Voltage
45.00
45.00
40.00
Charge Pump Voltage (V)
40.00
Charge Pump Voltage (V)
24 V
Supply Voltage (V)
C001
35.00
30.00
8V
25.00
24 V
27 V
20.00
35.00
30.00
25.00
-40°C
20.00
0°C
15.00
25°C
10.00
15.00
5.00
10.00
0.00
70°C
85°C
-40°C
0°C
25°C
70°C
8V
85°C
Temperature (ƒC)
600.00
500.00
500.00
400.00
400.00
Rdson (mŸ)
600.00
300.00
200.00
27 V
300.00
200.00
8V
100.00
C006
Figure 5. Charge Pump Voltage over Supply Voltage
Figure 4. Charge Pump Voltage over Temperature
Rdson (mŸ)
24 V
Supply Voltage (V)
C005
8V
100.00
24 V
24 V
27 V
27 V
0.00
0.00
-40°C
0°C
25°C
70°C
85°C
Temperature (ƒC)
-40°C
Figure 6. LS RDSON AOUT2 over Temperature
0°C
25°C
70°C
85°C
Temperature (ƒC)
C007
C008
Figure 7. LS RDSON A OUT1over Temperature
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600.00
600.00
500.00
500.00
400.00
400.00
Rdson (mŸ)
Rdson (mŸ)
Typical Characteristics (continued)
300.00
200.00
300.00
200.00
8V
100.00
8V
100.00
24 V
24 V
27 V
27 V
0.00
0.00
-40°C
0°C
25°C
70°C
85°C
Temperature (ƒC)
Figure 8. HS RDSON AOUT2 over Temperature
8
-40°C
0°C
25°C
70°C
85°C
Temperature (ƒC)
C009
C010
Figure 9. HS RDSON AOUT1 over Temperature
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7 Detailed Description
7.1 Overview
The DRV8821 is a dual stepper motor driver solution for applications that require independent control of two
different motors. The device integrates four NMOS H-bridges, a microstepping indexer, and various fault
protection features. The DRV8821 can be powered with a supply voltage between 8 and 32 V, and is capable of
providing an output current up to 1.5-A full scale. Actual full-scale current will depend on ambient temperature,
supply voltage, and PCB ground size.
A simple STEP/DIR interface allows easy interfacing to the controller circuit. The internal indexer is able to
execute high-accuracy microstepping without requiring the processor to control the current level. The indexer is
cable of full step and half step as well as microstepping to 1/4 and 1/8.
The current regulation is configurable with two different decay modes; slow decay and mixed decay. The mixed
decay mode uses slow decay on increasing current steps and mixed decay on decreasing current steps, while
slow decay mode will always use slow decay regardless increasing or decreasing steps.
The gate drive to each FET in all four H-Bridges is controlled to prevent any cross-conduction (shoot through
current) during transitions.
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7.2 Functional Block Diagram
CP1
Dig.
VCC
Charge
Pump and
Gat e Drive
Regulator
3.3V
Regulator
V3P3
0.47µF
6.3V
CP2
0.01µF
35V
+24
VCP
VGD
0.1µF
16V
VCP
·
ABVREF
VM
·
+24
0.1µF, 35V
AOUT1
PWM H-b ridge
driver A
Step
Motor
AOUT2
ABSTEP
AISEN
ABDIR
+24
ABENBLn
VM
ABUSM0
·
0.1µF, 35V
ABUSM1
BOUT1
PWM H-bridge
driver B
ABDECAY
BOUT2
ABRESETn
BISEN
I ndexer
Logic
+24
CDSTEP
VM
·
CDDIR
PWM H-bridge
driver C
CDENBLn
0.1µF, 35V
COUT1
CDUSM0
COUT2
CDUSM1
CI SEN
Step
Motor
CD DEC AY
+24
CDRESETn
VM
0.1µF, 35V
DOUT1
PWM H-bridge
driver D
CDVREF
·
DOUT2
DISEN
OCP
Thermal
Shut down
Oscillator
UVLO
RESET
GND
7.3 Feature Description
7.3.1 PWM Motor Drivers
The DRV8821 contains four H-bridge motor drivers with current-control PWM circuitry. A block diagram showing
drivers A and B of the motor control circuitry (as typically used to drive a bipolar stepper motor) is shown below.
Drivers C and D are the same as A and B (though the Rds(on) of the output FETs is different).
10
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Feature Description (continued)
VM
OC P
VM
VC P, VGD
A OU T1
From Indexer Logic
Predrive
AEN B L
Step
Motor
APH A SE
A OU T2
A BD EC A Y
PW M
OC P
A I[2:0]
3
+
A I[2:0]
A IS EN
A =5
DAC
3
A BVR EF
VM
OC P
VM
V CP, VGD
BOU T1
Predrive
B EN BL
B OU T2
BPH A SE
PW M
OC P
B ISEN
+
B I[2:0]
A =5
DAC
3
Figure 10. Block Diagram
Note that there are multiple VM motor power supply pins. All VM pins must be connected together to the motor
supply voltage.
7.3.2 Current Regulation
The PWM chopping current is set by a comparator which compares the voltage across a current sense resistor
connected to the xISEN pins, multiplied by a factor of 5, with a reference voltage. The reference voltage is input
from the xVREF pin.
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Feature Description (continued)
The full-scale (100%) chopping current is calculated as follows:
5
(1)
Example:
If a 0.5-Ω sense resistor is used and the VREFx pin is 2.5 V, the full-scale (100%) chopping current is
2.5 V/(5 × 0.5 Ω) = 1 A.
The reference voltage is also scaled by an internal DAC that allows torque control for fractional stepping of a
bipolar stepper motor, as described in Microstepping Indexer.
7.3.3 Blanking Time
After the current is enabled in an H-bridge, the voltage on the xISEN pin is ignored for a fixed period of time
before enabling the current sense circuitry. This blanking time is fixed at 3.75 μs. Note that the blanking time also
sets the minimum on time of the PWM.
7.3.4 Microstepping Indexer
Built-in indexer logic in the DRV8821 allows a number of different stepping configurations. The xUSM1 and
xUSM0 pins are used to configure the stepping format as shown in the table below:
Table 1. Microstepping Selection Bits
xUSM1
xUSM0
STEP MODE
0
0
Full step (2-phase excitation)
0
1
½ step (1-2 phase excitation)
1
0
1/4 step (W1-2 phase excitation)
1
1
Eight microsteps/steps
The following table shows the relative current and step directions for different settings of xUSM1 and xUSM0. At
each rising edge of the xSTEP input, the indexer travels to the next state in the table. The direction is shown with
the DIR pin high; if the xDIR pin is low the sequence is reversed. Positive current is defined as xOUT1 = positive
with respect to xOUT2.
Note that the home state is 45 degrees. This state is entered at power-up, during sleep mode, or application of
xRESETn.
Motor AB and motor CD act independently, and their indexer logic functions identically.
12
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Table 2. Microstepping Indexer
FULL STEP
xUSM = 00
1/4 STEP
xUSM = 10
1/8 STEP
xUSM = 11
1
1
1
100
0
0
2
98
20
11.25
3
92
38
22.5
4
83
56
33.75
5
71
71
45 (home state)
6
56
83
56.25
7
38
92
67.5
8
20
98
78.75
2
1
2
3
4
3
5
6
2
4
7
8
5
9
10
3
6
11
12
7
13
14
4
AOUTx
BOUTx
CURRENT
CURRENT
(% FULL-SCALE) (% FULL-SCALE)
½ STEP
xUSM = 01
8
15
16
STEP ANGLE
(DEGREES)
9
0
100
90
10
–20
98
101.25
11
–38
92
112.5
12
–56
83
123.75
13
–71
71
135
14
–83
56
146.25
15
–92
38
157.5
16
–98
20
168.75
17
–100
0
180
18
–98
–20
191.25
19
–92
–38
202.5
20
–83
–56
213.75
21
–71
–71
225
22
–56
–83
236.25
23
–38
–92
247.5
24
–20
–98
258.75
25
0
–100
270
26
20
–98
281.25
27
38
–92
292.5
28
56
–83
303.75
29
71
–71
315
30
83
–56
326.25
31
92
–38
337.5
32
98
–20
348.75
7.3.5 xRESETn and xENBLn Operation
The xRESETn pin, when driven active low, resets the step table to the home position. It also disables the Hbridge drivers. The xSTEP input is ignored while xRESETn is active. Note that there is a separate xRESETn pin
for each motor; each acts only on one of the two motor controllers.
The xENABLEn pin is used to control the output drivers. When xENBLn is low, the output H-bridges are enabled.
When xENBLn is high, the H-bridges are disabled and the outputs are in a high-impedance state.. Note that
there is a separate xENBLn pin for each motor; each acts only on one of the two motor drivers.
Note that when xENBLn is high, the input pins and control logic, including the indexer (xSTEP and xDIR pins) are
still functional.
Driving both ABENBLn and CDENBLn high will put the device into a low power sleep state. In this state, the Hbridges are disabled, both indexers are reset to the home state, the gate drive charge pump is stopped, and all
internal clocks are stopped. In this state all inputs are ignored until one or both of the xENBLn pits return active
low.
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7.3.6 Protection Circuits
The DRV8821 is fully protected against undervoltage, overcurrent and overtemperature events.
7.3.6.1 Overcurrent Protection (OCP)
All of the drivers in DRV8821 are protected with an OCP (Over-Current Protection) circuit.
The OCP circuit includes an analog current limit circuit, which acts by removing the gate drive from each output
FET if the current through it exceeds a preset level. This circuit will limit the current to a level that is safe to
prevent damage to the FET.
A digital circuit monitors the analog current limit circuits. If any analog current limit condition exists for longer than
a preset period, all drivers in the device will be disabled.
The device is re-enabled upon the removal and re-application of power at the VM pins.
7.3.6.2 Thermal Shutdown (TSD)
If the die temperature exceeds safe limits, all drivers in the device will be shut down.
The device will remain disabled until the die temperature has fallen to a safe level. After the temperature has
fallen, the device may be re-enabled upon the removal and re-application of power at the VM pin.
7.3.6.3 Undervoltage Lockout (UVLO)
If at any time the voltage on the VM pins falls below the undervoltage lockout threshold voltage, all circuitry in the
device will be disabled. Operation will resume when VM rises above the UVLO threshold. The indexer logic will
be reset to its initial condition in the event of an undervoltage lockout.
7.3.6.4 Shoot-Through Current Prevention
The gate drive to each FET in the H-bridge is controlled to prevent any cross-conduction (shoot through current)
during transitions.
7.4 Device Functional Modes
7.4.1 Decay Mode
The DRV8821 supports two different decay modes: slow decay or mixed decay. The mixed decay mode uses
slow decay on increasing steps and mixed decay on decreasing steps. Mixed decay mode begins as fast decay
but after a period of time (75% of the PWM cycle), switches to slow decay mode for the remainder of the fixed
PWM period.
During PWM current chopping, the H-bridge is enabled to drive through the motor winding until the PWM current
chopping threshold is reached. This is shown in Figure 11 as case 1. The current flow direction shown indicates
positive current flow in Figure 11.
Once the chopping current threshold is reached, the H-bridge can operate in two different states, fast decay or
slow decay.
In fast decay mode, once the PWM chopping current level has been reached, the H-bridge reverses state to
allow winding current to flow in a reverse direction. As the winding current approaches zero, the bridge is
disabled to prevent any reverse current flow. Fast-decay mode is shown in Figure 11 as case 2.
In slow-decay mode, winding current is re-circulated by enabling both of the low-side FETs in the bridge. This is
shown in Figure 11 as case 3.
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Device Functional Modes (continued)
VM
1 Drive current
1
xOUT2
xOUT1
3
2
Fast decay (reverse)
3
Slow decay (brake)
2
Figure 11. Decay Mode
The DRV8821 also supports a mixed decay mode. Mixed decay mode begins as fast decay, but after a period of
time (75% of the PWM cycle) switches to slow decay mode for the remainder of the fixed PWM period.
Mixed decay mode is only active if the current through the winding is decreasing (per the indexer step table); if
the current is increasing, then slow decay is always used.
Slow or mixed decay mode is selected by the state of the xDECAY pins - logic low selects slow decay, and logic
high selects mixed decay operation.
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The DRV8821 can be used to drive two bipolar stepper motors.
8.2 Typical Application
Figure 12. Typical Application Schematic
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Typical Application (continued)
8.2.1 Design Requirements
Table 3 shows the design parameters.
Table 3. Design Parameters
DESIGN PARAMETER
REFERENCE
EXAMPLE VALUE
Supply voltage
VM
24 V
Motor winding resistance
RL
7.4 Ω/phase
Motor step full angle
θstep
1.8°/step
Target microstepping angle
nm
1/8 step
Target motor speed
V
120 rpm
Target full-scale current
IFS
1A
8.2.2 Detailed Design Procedure
8.2.2.1 Stepper Motor Speed
The first step in configuring the DRV8821 requires the desired motor speed and stepping level. The DRV8821
can support from full step to 1/8 step mode. If the target motor speed is too high, the motor will not spin. Make
sure that the motor can support the target speed. For a desired motor speed (v), a microstepping level (nm), and
motor full step angle (θstep).
v (rpm) ´ 360 (° / rot)
ƒ step (steps / s) =
qstep (° / step) ´ nm (steps / mirostep) ´ 60 (s / min)
(2)
θstep can be found in the stepper motor data sheet or often written on the motor itself.
For DRV8821, the microstepping levels are set by the xUSM0/xUSM1 pins and can be any of the settings in
Table 1. Higher microstepping means a smoother motor motion and less audible noise, but increases the
switching losses and requires a higher ƒstep to achieve the same motor speed.
8.2.2.2 Current Regulation
The chopping current (ICHOP) is the maximum current driven through either winding. This quality will depend on
the sense resistor value (RXISEN).
VREFX
ICHOP =
5 ´ RISENSE
(3)
ICHOP is set by a comparator which compares the voltage across RXISEN to a reference voltage. Note that ICHOP
must follow Equation 4 to avoid saturating the motor.
VM (V )
ICHOP (A ) <
RL (W ) + 2 ´ RDS(ON) (W ) + RSENSE (W)
where
•
•
VM is the motor supply voltage.
RL is the motor winding resistance.
(4)
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8.2.3 Application Curves
18
Figure 13. ½ Step Microstepping with Slow Decay
Figure 14. 1/8 Step Microstepping with Slow Decay
Figure 15. 1/2 Step Microstepping with Mixed Decay
Figure 16. 1/8 Step Microstepping with Mixed Decay
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9 Power Supply Recommendations
9.1 Bulk Capacitance
Having appropriate local bulk capacitance is an important factor in motor drive system design. It is generally
beneficial to have more bulk capacitance, while the disadvantages are increased cost and physical size.
The amount of local capacitance needed depends on a variety of factors, including:
• The highest current required by the motor system.
• The power supply's capacitance and ability to source current.
• The amount of parasitic inductance between the power supply and motor system.
• The acceptable voltage ripple.
• The type of motor used (Brushed DC, Brushless DC, Stepper).
• The motor breaking method.
The inductance between the power supply and motor drive system will limit the rate current can change from the
power supply. If the local bulk capacitance is too small, the system will respond to excessive current demands or
dumps from the motor with a change in voltage. When adequate bulk capacitance is used, the motor voltage
remains stable and high current can be quickly supplied.
The datasheet generally provides a recommended value, but system-level testing is required to determine the
appropriate sized bulk capacitor.
Figure 17. Example Setup of Motor Drive System with External Power Supply
The voltage rating for bulk capacitors should be higher than the operating voltage, to provide margin for cases
when the motor transfers energy to the supply.
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10 Layout
10.1 Layout Guidelines
The bulk capacitor should be placed to minimize the distance of the high-current path through the motor driver
device. The connecting metal trace widths should be as wide as possible, and numerous vias should be used
when connecting PCB layers. These practices minimize inductance and allow the bulk capacitor to deliver high
current.
Small-value capacitors should be ceramic, and placed closely to device pins.
The high-current device outputs should use wide metal traces.
The device thermal pad should be soldered to the PCB top-layer ground plane. Multiple vias should be used to
connect to a large bottom-layer ground plane. The use of large metal planes and multiple vias help dissipate the
I2 × RDS(on) heat that is generated in the device.
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10.2 Layout Example
Figure 18. Typical Layout of DRV8821
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10.3 Thermal Considerations
The DRV8821 has thermal shutdown (TSD) as described Thermal Shutdown (TSD). If the die temperature
exceeds approximately 150°C, the device will be disabled until the temperature drops to a safe level.
Any tendency of the device to enter thermal shutdown is an indication of either excessive power dissipation,
insufficient heatsinking, or too high an ambient temperature.
10.3.1 Power Dissipation
Power dissipation in the DRV8821 is dominated by the power dissipated in the output FET resistance, or RDS(ON).
Average power dissipation when running a stepper motor can be roughly estimated by Equation 5.
PTOT = 4
·
RDS(ON)
·
(IOUT(RMS))
2
(5)
where PTOT is the total power dissipation, RDS(ON) is the resistance of each FET, and IOUT(RMS) is the RMS output
current being applied to each winding. IOUT(RMS) is equal to the approximately 0.7x the full-scale output current
setting. The factor of 4 comes from the fact that there are two motor windings, and at any instant two FETs are
conducting winding current for each winding (one high-side and one low-side). Remember that the DRV8821 has
two stepper motor drivers, so the power dissipation of each must be added together to determine the total device
power dissipation.
The maximum amount of power that can be dissipated in the DRV8821 is dependent on ambient temperature
and heatsinking. The thermal dissipation ratings table in the datasheet can be used to estimate the temperature
rise for typical PCB constructions.
Note that RDS(ON) increases with temperature, so as the device heats, the power dissipation increases. This must
be taken into consideration when sizing the heatsink.
10.3.2 Heatsinking
The PowerPAD™ package uses an exposed pad to remove heat from the device. For proper operation, this pad
must be thermally connected to copper on the PCB to dissipate heat. On a multi-layer PCB with a ground plane,
this can be accomplished by adding a number of vias to connect the thermal pad to the ground plane. On PCBs
without internal planes, copper area can be added on either side of the PCB to dissipate heat. If the copper area
is on the opposite side of the PCB from the device, thermal vias are used to transfer the heat between top and
bottom layers.
For details about how to design the PCB, refer to TI application report, PowerPAD™ Thermally Enhanced
Package SLMA002 and TI application brief, PowerPAD™ Made Easy, SLMA004 available at www.ti.com.
In general, the more copper area that can be provided, the more power can be dissipated. Figure 19 shows
thermal resistance vs. copper plane area for both a single-sided PCB with 2-oz copper heatsink area, and a 4layer PCB with 1-oz copper and a solid ground plane. Both PCBs are 76 mm x 114 mm, and 1.6 mm thick. It can
be seen that the heatsink effectiveness increases rapidly to about 20 cm2, then levels off somewhat for larger
areas.
Six pins on the center of each side of the package are also connected to the device ground. A copper area can
be used on the PCB that connects to the PowerPAD™ as well as to all the ground pins on each side of the
device. This is especially useful for single-layer PCB designs.
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Thermal Considerations (continued)
70
65
Thermal Resistance (RqJA) - °C/W
60
55
50
45
Low-K PCB (2 layer)
40
35
30
High-K PCB (4 layer with ground plane)
25
20
0
10
20
30
40
50
60
70
80
90
2
Backside Copper Area - cm
Figure 19. Thermal Resistance vs Copper Plane Area
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11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
For details about how to design the PCB, refer to TI application report, PowerPAD™ Thermally Enhanced
Package SLMA002 and TI application brief, PowerPAD™ Made Easy, SLMA004 available at www.ti.com.
11.2 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.3 Trademarks
PowerPAD, E2E are trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
11.4 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
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10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
DRV8821DCA
ACTIVE
HTSSOP
DCA
48
40
RoHS & Green
NIPDAU
Level-3-260C-168 HR
-40 to 85
DRV8821
DRV8821DCAR
ACTIVE
HTSSOP
DCA
48
2000
RoHS & Green
NIPDAU
Level-3-260C-168 HR
-40 to 85
DRV8821
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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