DRV8870_16 Datasheet, PDF (8/25 Pages) Texas Instruments – Brushed DC Motor Driver

DRV8870
SLVSCY8A – AUGUST 2015 – REVISED JANUARY 2016
www.ti.com
7.3 Feature Description
7.3.1 Bridge Control
The DRV8870 output consists of four N-channel MOSFETs that are designed to drive high current. They are
controlled by the two logic inputs IN1 and IN2, according to Table 1.
Table 1. H-Bridge Control
IN1
IN2
OUT1
OUT2
DESCRIPTION
0
0
High-Z
High-Z
Coast; H-bridge disabled to High-Z (sleep entered after 1 ms)
0
1
L
H
Reverse (Current OUT2 → OUT1)
1
0
H
L
Forward (Current OUT1 → OUT2)
1
1
L
L
Brake; low-side slow decay
The inputs can be set to static voltages for 100% duty cycle drive, or they can be pulse-width modulated (PWM)
for variable motor speed. When using PWM, it typically works best to switch between driving and braking. For
example, to drive a motor forward with 50% of its max RPM, IN1 = 1 and IN2 = 0 during the driving period, and
IN1 = 1 and IN2 = 1 during the other period. Alternatively, the coast mode (IN1 = 0, IN2 = 0) for fast current
decay is also available. The input pins can be powered before VM is applied.
VM
VM
1 Forward drive
1 Reverse drive
2 Slow decay (brake)
1
3 High-Z (coast)
2 Slow decay (brake)
1
3 High-Z (coast)
OUT1
OUT2
2
OUT1
OUT2
2
3
3
FORWARD
REVERSE
Figure 4. H-Bridge Current Paths
7.3.2 Sleep Mode
When IN1 and IN2 are both low for time t_SLEEP (typically 1 ms), the DRV8870 enters a low-power sleep mode,
where the outputs remain High-Z and the device uses I_VMSLEEP (microamps) of current. If the device is powered
up while both inputs are low, sleep mode is immediately entered. After IN1 or IN2 are high for at least 5 µs, the
device will be operational 50 µs (t_ON) later.
7.3.3 Current Regulation
The DRV8870 limits the output current based on the analog input VREF and the resistance of an external sense
resistor on pin ISEN, according to this equation:
8
Submit Documentation Feedback
Product Folder Links: DRV8870
Copyright © 2015–2016, Texas Instruments Incorporated