ZHCS276F September 2011 – February 2025 DRV8818
PRODUCTION DATA
- 1
- 1 特性
- 2 應用
- 3 說明
- 4 Pin Configuration and Functions
- 5 Specifications
- 6 Detailed Description
- 7 Application and Implementation
- 8 Device and Documentation Support
- 9 Revision History
- 10Mechanical, Packaging, and Orderable Information
封裝選項
機械數據 (封裝 | 引腳)
- PWP|28
散熱焊盤機械數據 (封裝 | 引腳)
- PWP|28
訂購信息
6.3.2 Current Regulation
The PWM chopping current is set by a comparator, which compares the voltage across a current sense resistor, multiplied by a factor of 8, with a reference voltage. The reference voltage is input from the VREF pin. The full-scale (100%) chopping current is calculated as follows:
Example:
If a 0.22? sense resistor is used and the VREFx
pin is 3.3V, the full-scale (100%) chopping current is
3.3V /
(8 × 0.22?) = 1.875A.
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 the Section 6.3.4 section.
When a winding is activated, the current through the winding rises until the chopping current threshold described above is reached, then the current is switched off for a fixed off time. The off time is determined by the values of a resistor and capacitor connected to the RCA (for bridge A) and RCB (for bridge B) pins. The off time is approximated by:
To avoid falsely tripping on transient currents when the winding is first activated, a blanking period is used immediately after turning on the FETs, during which the state of the current sense comparator is ignored. The blanking time is determined by the value of the capacitor connected to the RCx pin and is approximated by:
