电子知识_TI的DRV8846是高度集成的步进马达驱动器方案

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TI的DRV8846是高度集成的步进马达驱动器方案

来源：互联网 | 作者:中华IC网整理 | 发表于：2014-12-15

TI公司的DRV8846是高度集成的步进马达驱动器,包括两个H桥和微步进分度器,工作电压4-18V,驱动电流高达1A,主要用在打印机,扫描仪,视频安全摄像机和投映仪.本文介绍了DRV8846主要特性,功能框图,应用电路以及评估板主要特性,电路图和材料清单,以及3D打印机控制器(12V)主要特性,电路图和材料清单.

DRV8846 双通道 H 桥步进电机驱动器
DRV8846 Dual H-Bridge Stepper Motor Driver

The DRV8846 provides a highly-integrated stepper motor driver for cameras, printers, projectors, and other automated equipment applications. The device has two H-bridges and a microstepping indexer and is intended to drive a bipolar stepper motor. The output block of each H-bridge driver consists of N- channel and P-channel power MOSFETs configured as full H-bridges to drive the motor windings. The DRV8846 is capable of driving up to 1-A full scale
output current (with proper heatsinking and TA = 25℃).

A simple STEP/DIR interface allows easy interfacing to controller circuits. Pins allow configuration of the motor in full-step up to 1/32-step modes. Decay mode is configurable so that adaptive decay, slow decay, fast decay, and mixed decay can be used. The PWM
current chopping off-time can also be selected. A low-power sleep mode is provided which shuts down internal circuitry to achieve very-low quiescent current draw. This sleep mode can be set using a dedicated nSLEEP pin.

Internal protection functions are provided for UVLO,overcurrent protection, short circuit protection, and overtemperature. Fault conditions are indicated via a nFAULT pin.

DRV8846主要特性:

1• PWM Microstepping Motor Driver
– Built-In Microstepping Indexer
– Up to 1/32 Microstepping
– Step/Direction Control
• Multiple Decay Modes
– Adaptive Decay
– Mixed Decay
– Slow Decay
– Fast Decay
• Configurable Off-Time PWM Chopping
– 10-, 20-, or 30-μs Off-Time
• Adaptive Blanking Time for Smooth Stepping
• 4- to 18-V Operating Supply Voltage Range
• 1-A Continuous/RMS Output Current (at 25℃)
• Low-Current Sleep Mode
• 3-Bit Torque DAC to Scale Motor Current
• Thermally Enhanced Surface Mount Package
• Protection Features
– VM Undervoltage Lockout (UVLO)
– Overcurrent Protection (OCP)
– Thermal Shutdown (TSD)
– Fault Condition Indication Pin (nFAULT)
DRV8846主要应用:
• Printers
• Scanners
• Video Security Cameras

• Projectors

图1. DRV8846功能框图

图2. DRV8846 PWM马达驱动器电路图

图3. DRV8846 典型应用电路图

评估板

The DRV8846 customer EVM is a platform revolving around the DRV8846, a low voltage dual H-bridge driver and highly configurable power stage. This device has been optimized to drive a single bipolar stepper with up to 32 degrees of internally generated microstepping.

The EVM houses an MSP430 microcontroller and a USB interface chip. The USB chip allows for serial communications from a PC computer where a Microsoft® Windows® application is used to schedule serial commands. These commands can be used to control each of the device’s signals, and drive the stepper motor by issuing the step commands at the desired rate.

The microcontroller firmware operates using internal index mode.

This user’s guide details the operation of the EVM, as well as the hardware configurability of the evaluation module.

图4.评估板PCB外形图

图5.评估板连接图

图6.评估板电路图(1)

图7.评估板电路图(2)
评估板材料清单:

3D打印机控制器(12V)

This design is a complete system for controlling 3-axis, single extruder-based 3D printers. The system is managed by the MSP430F5529 LaunchPad and utilizes the DRV8846 for precision stepper motor control. The CSD18534Q5A is used as a low-side switch for the hot bed heater, extruder heater, and cooling fan. The DRV5033 Hall Sensor acts as a contactless limit switch.

3D打印机控制器(12V)主要特性:

Complete 3D printer controller with MCU, stepper drivers, heater outputs, sensor inputs, and SD card slot.
Precise stepper motor current regulation using DRV8846 adaptive decay
Hall sensor limit switches are immune to contaminants and never wear out
High-current heater outputs from the CSD18534Q5A with low 7.8 mΩ Rds(ON)
Powered from a single 12V supply
System has been fully tested and proven

图8.3D打印机TIDA-00405外形图

图9.3D打印机TIDA-00405电路图(1)

图10.3D打印机TIDA-00405电路图(2)

图11.3D打印机TIDA-00405电路图(3)

图12.3D打印机TIDA-00405电路图(4)

图13.3D打印机TIDA-00405电路图(5)
3D打印机TIDA-00405系统材料清单:

参考资料：

Detailed Description

1 Overview

The DRV8846 is an integrated motor driver solution for bipolar stepper motors. The device integrates 2 H-bridges that use NMOS low-side drivers and PMOS high-side drivers, current sense regulation circuitry, and a microstepping indexer. The DRV8846 can be powered with a supply range between 4 to 18 V and is capable of providing an output current to 1.4-A full scale or 1-A rms.

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 PWM off-time, tOFF can be adjusted to 10, 20, or 30 μs.

The DRV8846 has an adaptive decay feature that automatically adjusts the decay setting to minimize current ripple while still reacting quickly to step changes. This feature allows the DRV8846 to quickly be integrated into a system.

A torque DAC feature allows the controller to scale the output current without needing to scale the analog reference voltage input VREF. The torque DAC is accessed using digital input pins. This allows the controller to save power by decreasing the current consumption when not required.

A low-power sleep mode is included, which allows the system to save power when not driving the motor.

2 Functional Block Diagram

3 Feature Description

3.1 PWM Motor Drivers

DRV8846 contains two identical H-bridge motor drivers with current-control PWM circuitry. Figure 6 shows a block diagram of the circuitry.

Figure 6. PWM Motor Driver Circuitry

3.2 Micro-Stepping Indexer

To allow a simple step and direction interface to control stepper motors, the DRV8846 contains a microstepping indexer. The indexer controls the state of the H-bridges automatically. When the correct transition is applied at the STEP input, the indexer moves to the next step, according to the direction set by the DIR pin. In 1/8, 1/16, and 1/32 step modes, both the rising and falling edges of the STEP input may be used to advance the indexer, depending on the M0 / M1 setting.

The nENBL pin disables the output stage in indexer mode. When nENBL = 0, the indexer inputs are still active and respond to the STEP and DIR input pins; only the output stage is disabled.

The indexer logic in the DRV8846 allows a number of different stepping configurations. The M0 and M1 pins configure the stepping format (see Table 2).

Table 2. Step Mode Settings

M1	M0	STEP MODE
0	0	Full step (2-phase excitation), rising-edge only
0	Z	1/2 step (1-2 phase excitation), rising-edge only
0	1	1/4 step (W1-2 phase excitation), rising-edge only
Z	0	8 microsteps/step, rising-edge only
Z	Z	8 microsteps/step, rising and falling edges
Z	1	16 microsteps/step, rising-edge only
1	0	16 microsteps/step, rising and falling edges
1	Z	32 microsteps/step, rising-edge only
1	1	32 microsteps/step, rising and falling edges

Note that the M0 and M1 pins are tri-level inputs. These pins can be driven logic low, logic high, or high-impedance (Z), like the I0 and I1 pins described previously.

For 1/8, 1/16, and 1/32-step modes, selections are available to advance the indexer only on the rising edge of the STEP input, or on both the rising and falling edges.

The step mode may be changed on-the-fly while the motor is moving. The indexer advances to the next valid state for the new M0 / M1 setting at the next rising edge of STEP.

The home state is 45°. The indexer enters the home state after power-up, after exiting UVLO, or after exiting sleep mode (see the yellow-shaded cells in Table 3 also indicated with a table note).

Table 3 shows the relative current and step directions for different step mode settings. At each rising edge of the STEP input, the indexer travels to the next state in the table. The direction is shown with the DIR pin high; if the DIR pin is low, the sequence is reversed. Positive current is defined as xOUT1 = positive with respect to xOUT2.

Table 3. Relative Current and Step Directions

1/32 STEP	1/16 STEP	1/8 STEP	1/4 STEP	1/2 STEP	FULL STEP 70%	WINDING CURRENT A	WINDING CURRENT B	ELECTRICAL ANGLE
1	1	1	1	1		100%	0%	0
2						100%	5%	3
3	2					100%	10%	6
4						99%	15%	8
5	3	2				98%	20%	11
6						97%	24%	14
7	4					96%	29%	17
8						94%	34%	20
9	5	3	2			92%	38%	23
10						90%	43%	25
11	6					88%	47%	28
12						86%	51%	31
13	7	4				83%	56%	34
14						80%	60%	37
15	8					77%	63%	39
16						74%	67%	42
17(1)	9(1)	5(1)	3(1)	2(1)	1(1)	71%	71%	45
18						67%	74%	48
19	10					63%	77%	51
20						60%	80%	53
21	11	6				56%	83%	56
22						51%	86%	59
23	12					47%	88%	62
24						43%	90%	65
25	13	7	4			38%	92%	68
26						34%	94%	70
27	14					29%	96%	73
28						24%	97%	76
29	15	8				20%	98%	79
30						15%	99%	82
31	16					10%	100%	84
32						5%	100%	87
33	17	9	5	3		0%	100%	90
34						–5%	100%	93
35	18					–10%	100%	96
36						–15%	99%	98
37	19	10				–20%	98%	101
38						–24%	97%	104
39	20					–29%	96%	107
40						–34%	94%	110
41	21	11	6			–38%	92%	113
42						–43%	90%	115
43	22					–47%	88%	118
44						–51%	86%	121
45	23	12				–56%	83%	124
46						–60%	80%	127
47	24					–63%	77%	129
48						–67%	74%	132
49	25	13	7	4	2	–71%	71%	135
50						–74%	67%	138
51	26					–77%	63%	141
52						–80%	60%	143
53	27	14				–83%	56%	146
54						–86%	51%	149
55	28					–88%	47%	152
56						–90%	43%	155
57	29	15	8			–92%	38%	158
58						–94%	34%	160
59	30					–96%	29%	163
60						–97%	24%	166
61	31	16				–98%	20%	169
62						–99%	15%	172
63	32					–100%	10%	174
64						–100%	5%	177
65	33	17	9	5		–100%	0%	180
66						–100%	–5%	183
67	34					–100%	–10%	186
68						–99%	–15%	188
69	35	18				–98%	–20%	191
70						–97%	–24%	194
71	36					–96%	–29%	197
72						–94%	–34%	200
73	37	19	10			–92%	–38%	203
74						–90%	–43%	205
75	38					–88%	–47%	208
76						–86%	–51%	211
77	39	20				–83%	–56%	214
78						–80%	–60%	217
79	40					–77%	–63%	219
80						–74%	–67%	222
81	41	21	11	6	3	–71%	–71%	225
82						–67%	–74%	228
83	42					–63%	–77%	231
84						–60%	–80%	233
85	43	22				–56%	–83%	236
86						–51%	–86%	239
87	44					–47%	–88%	242
88						–43%	–90%	245
89	45	23	12			–38%	–92%	248
90						–34%	–94%	250
91	46					–29%	–96%	253
92						–24%	–97%	256
93	47	24				–20%	–98%	259
94						–15%	–99%	262
95	48					–10%	–100%	264
96						–5%	–100%	267
97	49	25	13	7		0%	–100%	270
98						5%	–100%	273
99	50					10%	–100%	276
100						15%	–99%	278
101	51	26				20%	–98%	281
102						24%	–97%	284
103	52					29%	–96%	287
104						34%	–94%	290
105	53	27	14			38%	–92%	293
106						43%	–90%	295
107	54					47%	–88%	298
108						51%	–86%	301
109	55	28				56%	–83%	304
110						60%	–80%	307
111	56					63%	–77%	309
112						67%	–74%	312
113	57	29	15	8	4	71%	–71%	315
114						74%	–67%	318
115	58					77%	–63%	321
116						80%	–60%	323
117	59	30				83%	–56%	326
118						86%	–51%	329
119	60					88%	–47%	332
120						90%	–43%	335
121	61	31	16			92%	–38%	338
122						94%	–34%	340
123	62					96%	–29%	343
124						97%	–24%	346
125	63	32				98%	–20%	349
126						99%	–15%	352
127	64					100%	–10%	354
128						100%	–5%	357

(1) The indexer enters the home state after power-up, after exiting UVLO, or after exiting sleep mode.

3.3 Current Regulation

The current through the motor windings is regulated by an adjustable fixed-off-time PWM current regulation circuit. When an H-bridge is enabled, current rises through the winding at a rate dependent on the DC voltage, inductance of the winding, and the magnitude of the back EMF present. After the current reaches the current chopping threshold, the bridge enters a decay mode for a fixed period of time to decrease the current, which is configurable between 10 to 30 μs through the tri-level input TOFF_SEL. After the time expires, the bridge is re-enabled, starting another PWM cycle.

Table 4. Fixed Off-Time Selection

TOFF_SEL	TOFF Duration
0	20 μs
Z	10 μs
1	30 μs

The PWM chopping current is set by a comparator which compares the voltage across a current sense resistor connected to the xISEN pin, with a reference voltage. The reference voltage can be supplied by an internal reference of 3.3 V (which requires VINT to be connected to VREF), or externally supplied to the VREF pin. The reference voltage is then scaled first by the 3-bit torque DAC, then by the output of a sine lookup table that is applied to a sine-weighted DAC (sine DAC). The voltage is attenuated by a factor of 6.6.

The full-scale (100%) chopping current is calculated as follows:

Equation 1.

where

IFS is the full scale regulated current
VREF is the voltage on the VREF pin
RISENSE is the resistance of the sense resistor
TORQUE is the scaling percentage from the torque DAC.

Example: Using VREF is 3.3 V, torque DAC = 100%, and a 500-mΩ sense resistor, the full-scale chopping current is 3.3 V / (6.6 × 500 mΩ) × 100% = 1 A.

The current for both motor windings is scaled depending on the I0 and I1 pins, which drive a 3-bit linear DAC, as inTable 5.

Table 5. Torque DAC Settings

I1	I0	CURRENT SCALING (TORQUE)
0	0	100%
0	Z	87.5%
0	1	75%
Z	0	62.5%
Z	Z	50%
Z	1	37.5%
1	0	25%
1	Z	12.5%
1	1	0% (outputs disabled)

Table 6 gives the xISEN trip voltage at a given DAC code and I[1:0] setting.

Table 6. Torque DAC xISENS Trip Levels (VREF = 3.3 V)

Sine DAC Code	Torque DAC I[1:0] Setting
Sine DAC Code	00 - 100%	0Z - 87.5%	01 - 75%	Z0 - 62.5%	ZZ - 50%	Z1 - 37.5%	10 - 25%	1Z - 12.5%
31	500 mV	438 mV	375 mV	313 mV	250 mV	188 mV	125 mV	63 mV
30	500 mV	438 mV	375 mV	313 mV	250 mV	188 mV	125 mV	63 mV
29	495 mV	433 mV	371 mV	309 mV	248 mV	186 mV	124 mV	62 mV
28	490 mV	429 mV	368 mV	306 mV	245 mV	184 mV	123 mV	61 mV
27	485 mV	424 mV	364 mV	303 mV	243 mV	182 mV	121 mV	61 mV
26	480 mV	420 mV	360 mV	300 mV	240 mV	180 mV	120 mV	60 mV
25	470 mV	411 mV	353 mV	294 mV	235 mV	176 mV	118 mV	59 mV
24	460 mV	403 mV	345 mV	288 mV	230 mV	173 mV	115 mV	58 mV
23	450 mV	394 mV	338 mV	281 mV	225 mV	169 mV	113 mV	56 mV
22	440 mV	385 mV	330 mV	275 mV	220 mV	165 mV	110 mV	55 mV
21	430 mV	376 mV	323 mV	269 mV	215 mV	161 mV	108 mV	54 mV
20	415 mV	363 mV	311 mV	259 mV	208 mV	156 mV	104 mV	52 mV
19	400 mV	350 mV	300 mV	250 mV	200 mV	150 mV	100 mV	50 mV
18	385 mV	337 mV	289 mV	241 mV	193 mV	144 mV	96 mV	48 mV
17	370 mV	324 mV	278 mV	231 mV	185 mV	139 mV	93 mV	46 mV
16	355 mV	311 mV	266 mV	222 mV	178 mV	133 mV	89 mV	44 mV
15	335 mV	293 mV	251 mV	209 mV	168 mV	126 mV	84 mV	42 mV
14	315 mV	276 mV	236 mV	197 mV	158 mV	118 mV	79 mV	39 mV
13	300 mV	263 mV	225 mV	188 mV	150 mV	113 mV	75 mV	38 mV
12	280 mV	245 mV	210 mV	175 mV	140 mV	105 mV	70 mV	35 mV
11	255 mV	223 mV	191 mV	159 mV	128 mV	96 mV	64 mV	32 mV
10	235 mV	206 mV	176 mV	147 mV	118 mV	88 mV	59 mV	29 mV
9	215 mV	188 mV	161 mV	134 mV	108 mV	81 mV	54 mV	27 mV
8	190 mV	166 mV	143 mV	119 mV	95 mV	71 mV	48 mV	24 mV
7	170 mV	149 mV	128 mV	106 mV	85 mV	64 mV	43 mV	21 mV
6	145 mV	127 mV	109 mV	91 mV	73 mV	54 mV	36 mV	18 mV
5	120 mV	105 mV	90 mV	75 mV	60 mV	45 mV	30 mV	15 mV
4	100 mV	88 mV	75 mV	63 mV	50 mV	38 mV	25 mV	13 mV
3	75 mV	66 mV	56 mV	47 mV	38 mV	28 mV	19 mV	9 mV
2	50 mV	44 mV	38 mV	31 mV	25 mV	19 mV	13 mV	6 mV
1	25 mV	22 mV	19 mV	16 mV	13 mV	9 mV	6 mV	3 mV
0	0 mV	0 mV	0 mV	0 mV	0 mV	0 mV	0 mV	0 mV

3.4 Decay Mode

After the chopping current threshold is reached, the drive current is interrupted, but due to the inductive nature of the motor, current must continue to flow for some period of time (called recirculation current). To handle this recirculation current, the H-bridge can operate in two different states, fast decay or slow decay (or a mixture of fast and slow decay).

In fast-decay mode, after the PWM chopping current level is reached, the H-bridge reverses state to allow winding current to flow through the opposing FETs. As the winding current approaches 0, the bridge is disabled to prevent any reverse current flow. For fast-decay mode, see number 2 in Figure 7.

In slow-decay mode, winding current is recirculated by enabling both of the low-side FETs in the bridge. For slow-decay mode, see number 3 in Figure 7.

Figure 7. Decay Modes

The DRV8846 supports fast, slow, mixed, and adaptive decay modes. With stepper motors, the decay mode is chosen for a given stepper motor and operating conditions to minimize mechanical noise and vibration.

In mixed decay mode, the current recirculation begins as fast decay, but at a fixed period of time (determined by the state of the DEC1 and DEC0 pins shown in Table 7) the current recirculation switches to slow decay mode for the remainder of the fixed PWM period. Note that the DEC1 and DEC0 pins are tri-level inputs; these pins can be driven logic low, logic high, or high-impedance (Z).

Figure 8 shows the current waveforms in slow, fast, and 25% and 1 tBLANK mixed decay modes.

Figure 8. Decay Behavior

Table 7. Decay Pins Configuration

DEC1	DEC0	Decay Mode (Increasing Current)	Decay Mode (Decreasing Current)
0	0	Slow decay	Slow decay
0	Z	Slow decay	Mixed decay: 25% fast
0	1	Slow decay	Mixed decay: 1 tBLANK
Z	0	Mixed decay: 1 tBLANK	Mixed decay: 1 tBLANK
Z	Z	Mixed decay: 50% fast	Mixed decay: 50% fast
Z	1	Mixed decay: 25% fast	Mixed decay: 25% fast
1	0	Slow decay	Mixed decay: 50% fast
1	Z	Slow decay	Mixed decay: 12.5% fast
1	1	Slow decay	Fast decay

Figure 9 shows increasing and decreasing current. When current is decreasing, the decay mode used is fast, slow, or mixed as commanded by the DEC1 and DEC0 pins. Three DEC pin selections allow for mixed decay during increasing current.

Figure 9. Increasing and Decreasing Current

Adaptive decay mode simplifies the decay mode selection by dynamically changing to adjust for current level, step change, supply variation, BEMF, and load. To enable adaptive decay mode, pull the ADEC pin to logic high and pull DEC0 and DEC1 pins to logic high. The state of the ADEC pin is only evaluated when exiting sleep mode.

Adaptive decay adjusts the time spent in fast decay to minimize current ripple and quickly adjust to current-step changes. If the drive time is longer than the minimum (tBLANK), in order to reach the current trip point, the decay mode applied is slow decay (see Figure 10).

Figure 10. Adaptive Decay – Slow Decay Operation

When the minimum drive time (tBLANK) provides more current than the regulation point, fast decay of 1- tBLANK is applied. If the second drive period also provides more current than the regulation point, fast decay of 2 tBLANK is applied. If a third (or more) consecutive period provides more current than the regulation point, fast decay using 25% of tOFF time is applied. When the minimum drive time is insufficient to reach the current regulation level, slow decay is applied until the current exceeds the current reference level (see Figure 11).

Figure 11. Adaptive Decay – Mixed Decay Operation

Figure 12 shows a case for adaptive decay where a step occurs. The system starts with 1 tBLANK of fast decay and works up to 25% of tOFF time for fast decay until the current is regulated again.

Figure 12. Adaptive Decay – Step Operation

3.5 Blanking Time

After the current is enabled in an H-bridge, the voltage on the xISEN pin is ignored for a period of time before enabling the current sense circuitry. Note that the blanking time also sets the minimum drive time of the PWM.

The time, tBLANK, is determined by the sine DAC code and the torque DAC setting. The timing information for tBLANK is given in Table 8.

Table 8. tBLANK Settings

Sine DAC Code	Torque DAC I[1:0] Setting
Sine DAC Code	00 - 100%	0Z - 87.5%	01 - 75%	Z0 - 62.5%	ZZ - 50%	Z1 - 37.5%	10 - 25%	1Z - 12.5%
31	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
30	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
29	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
28	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
27	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
26	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
25	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
24	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
23	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
22	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
21	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
20	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
19	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
18	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
17	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
16	1.80 μs	1.80 μs	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	0.90 μs
15	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs
14	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs
13	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs
12	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs
11	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs
10	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs
9	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs
8	1.50 μs	1.50 μs	1.50 μs	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs
7	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs
6	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs
5	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs
4	1.20 μs	1.20 μs	1.20 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs
3	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs
2	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs
1	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs
0	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs	0.90 μs

3.6 Protection Circuits

The DRV8846 is fully protected against undervoltage, overcurrent, and overtemperature events.

3.6.1 Overcurrent Protection (OCP)

An analog current limit circuit on each FET limits the current through the FET by limiting the gate drive. If this analog current limit persists for longer than the OCP deglitch time tOCP, all FETs in the H-bridge are disabled and the nFAULT pin is driven low. The device remains disabled until the retry time, tRETRY, occurs. The OCP is independent for each H-bridge.

Overcurrent conditions are detected independently on both high-side and low-side devices; that is, a short to ground, supply, or across the motor winding all result in an OCP event. Note that OCP does not use the current sense circuitry used for PWM current control, so OCP functions without the presence of the xISEN resistors.

3.6.2 Thermal Shutdown (TSD)

If the die temperature exceeds safe limits, all FETs in the H-bridge are disabled and the nFAULT pin is driven low. After the die temperature falls to a safe level, operation automatically resumes. The nFAULT pin is released after operation has resumed.

3.6.3 Undervoltage Lockout (UVLO)

If at any time the voltage on the VM pin falls below the UVLO falling threshold voltage, VUVLO, all circuitry in the device is disabled, and all internal logic is reset. Operation resumes when VM rises above the UVLO rising threshold. The nFAULT pin is driven low during an undervoltage condition and is released after operation has resumed.

Table 9. Fault Behavior

Fault	Error Report	H-Bridge	Internal Circuits	Recovery
VM UVLO	nFAULT unlatched	Disabled	Shut down	System and fault clears on recovery
OCP	nFAULT unlatched	Disabled	Operating	System and fault clears on recovery and motor is driven after time, tRETRY
TSD	nFAULT unlatched	Disabled	Operating	System and fault clears on recovery