DRV8701_15 Datasheet, PDF (27/42 Pages) Texas Instruments – DRV8701 Brushed DC Motor Full-Bridge Gate Driver

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DRV8701
SLVSCX5B – MARCH 2015 – REVISED JULY 2015
7.4.1 Operating DRV8701 and H-Bridge on Separate Supplies
The DRV8701 can operate with a different supply voltage (VM) than the system H-bridge supply (VBAT). Case 1
describes normal operation when VM and VBAT are roughly the same. Special considerations must be taken into
account for Cases 2, 3, and 4.
• Case 1: VM ≈ VBAT. Recommended operation
• Case 2: VM > VBAT. IDRIVE must be shorted to AVDD to disable the high-side OCP. The IDRIVE current is
fixed at 25-mA source and 50-mA sink. This case can allow the driver to better enhance the external FETs for
VBAT < 11.5 V, or operate down to a lower supply voltage below 5.9 V.
• Case 3: VM > VBAT (higher than Case 2). IDRIVE must be shorted to AVDD to disable the high-side OCP.
This case can also allow the driver to better enhance the external FETs, or operate down to a lower supply
voltage below 5.9 V. The IDRIVE current is fixed at 25-mA source and 50-mA sink. Excess gate drive current
may be driven through the DRV8701 gate clamps causing additional power dissipation in the DRV8701.
• Case 4: VM < VBAT. The high-side FETs may not be in saturation. There may be a significant voltage drop
across the high-side FET when driving current. This causes high power dissipation in the external FET. When
operating in Case 4, the external FET threshold voltage must be greater than 2 V. Otherwise the DRV8701
will report a pre-driver fault whenever the FET is out of saturation.
VBAT Range
1 V ≤ VBAT < 5.9 V
5.9 V ≤ VBAT < 6.4 V
6.4 V ≤ VBAT < 11.5 V
11.5 V ≤ VBAT < 14 V
14 V ≤ VBAT ≤ 45 V
Table 9. VM Operational Range based on VBAT
Case 3
Case 2
VM ≥ 0.5 × VBAT + 5.75 V
VM ≤ 45 V
VM ≥ 5.9 V
VM < 0.5 × VBAT + 5.75 V
VM > VBAT
VM < 0.5 × VBAT + 5.75 V
VM > VBAT
VM ≤ 45 V
N/A
Case 1
N/A
VM = VBAT
VM > 0.6 × VBAT + 2.5 V
VM ≤ VBAT
VM > VBAT – 4 V
VM ≤ VBAT
Case 4
N/A
VM ≥ 5.9 V
VM < VBAT
VM ≥ 5.9 V
VM ≤ 0.6 × VBAT + 2.5 V
VM ≥ 5.9 V
VM ≤ VBAT – 4 V
Figure 33. VM Operating Range Based on Motor Supply Voltage
When nSLEEP is low, VM may be reduced down to 0 V with up to 45 V present at VBAT. However, nSLEEP
should not be brought high until VM is supplied with a voltage aligning with one of the cases outlined above.
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