Programmable electronic power breaker for 12 V bus
Document overview
- Manufacturer or author: STMICROELECTRONICS
- PDF pages: 23
Technical content
Datasheet sections
- 1 Diagram
- 2 Pin configuration
- 3 Maximum ratings
- 4 Electrical characteristics
- 5 Typical application diagram
- 6 Typical characteristics
- 7 The STPW12 detailed description
- 7.1 Power breaker intervention and thermal shutdown
- 7.2 Current limit and thermal protections
- 7.3 Monitor/fault pin description
- 7.4 Auto-retry delay time setting
- 7.5 PWM mode description, masking time
- 7.6 Details about the start-up sequence
- 8 Application guidelines
- 8.1 Power supply voltage
- 8.2 Input and output capacitors
- 8.3 Additional protections and layout guidelines
- 9 Package information
- 9.1 Power SO8 package information
Features
- Real-time input power sensing
- Input voltage range: from 10.5 V to 18 V
- Continuous current typ.: 1.5 A
- P-channel on resistance typ.: 50 mΩ
- Power limit accuracy typ.: 3%
- Undervoltage lockout
- Adjustable power limitation
- PWM mode
- Programmable power limit masking time
- Programmable auto-retry delay
- Thermal shutdown
- Enable function
- Short-circuit current limit
- Operative junction temp. - 40 °C to 125 °C
- Available in power SO8 package
- Simplifies UL compliance and certification
Applications
- White goods
- Consumer electronics
- Industrial applications
- Air contidioner
- User interface
- Fan motor control
Description
The STPW12 is an integrated electronic power breaker, optimized to monitor the input power. Connected in series to the power rail, it is able to disconnect the electronic circuitry on its output if the power consumption overcomes the programmed limit. When this happens, the device automatically opens the integrated power switch and disconnects the load. The intervention of the protection is communicated to the board monitoring circuits through a signal on the fault pin. After a certain delay time, programmable by the user, the device automatically tries again to close the internal switch and re-connect the load. A dedicated monitor pin provides the user with continuous information on the monitored power. The device can be enabled/disabled through a dedicated pin, and a direct PWM mode can be implemented providing PWM pin with an external signal. Maturity status link STPW12 Device summary Order code STPW12PHR Programmable electronic power breaker for 12 V bus STPW12 Datasheet DS12478 - Rev 1 - March 2018 For further information contact your local STMicroelectronics sales office.
This approach allows the user to optimize the design power distribution system, in terms of accurate power control, choice of isolation material, safety improvement, such as: reduced risk of flammability and easier qualification and certification flow. STPW12 DS12478 - Rev 1 page 2/23
1 Diagram
Figure 2. Block diagram
2 Pin configuration
Figure 3. Pin connection (top view) Table 1. Pin description
1 RSET An RS resistor between this pin and GND fixes the power limiting threshold
2 VIN Input voltage
3 PWM A PWM signal can be provided through this pin to turn-ON/OFF the power switch
4 Monitor/fault Power monitor signal, fault signal
5 CSET A CS capacitor between this pin and GND sets the auto-retry delay
6 Enable Enable pin (device active when EN=high)
7 VOUT Output pin
3 Maximum ratings
Table 2. Absolute maximum ratings
- The thermal shutdown limit is set above the maximum thermal ratings. It is not recommended to operate the device at
temperatures greater than the maximum ratings for extended periods of time. operation under these conditions is not implied. Table 3. Thermal data
4 Electrical characteristics
VIN = 12 V, VEN = VPWM = 5 V, CI = 10 µF, CO = 10 µF, TJ = 25 °C (unless otherwise specified). Table 4. Electrical characteristics
- Values over the temperature range are guaranteed by design/correlation and tested in production only at ambient
- Guaranteed by design, but not tested in production.
Electrical characteristics
5 Typical application diagram
Figure 4. Application circuit Figure 5. Application diagram
6 Typical characteristics
VIN = 12 V, ILOAD = 1 A, VEN = VPWM = 5 V, CI = 10 μF, CO = 10 μF, TJ = 25 °C (unless otherwise specified). Figure 6. Monitor signal vs. power Figure 7. Masking time, fault signal Figure 8. On resistance vs. temperature Figure 9. UVLO thresholds vs. temperature
7 The STPW12 detailed description
7.1 Power breaker intervention and thermal shutdown
The device disconnects the load if the power overcomes the pre-set threshold. can be chosen with the help of the Figure 15. Power limit threshold vs. RS graph and can be rated for ¼ W. precision resistors, the lower precision of the power limit. signal and Section 7.3 Monitor/fault pin description). auto-retry cycle starts with the defined masking time.
7.2 Current limit and thermal protections
The STPW12 is equipped with internal self-protections, such as: current limit and thermal shutdown. Once the die temperature decreases to the hysteresis value, the device automatically attempts to restart. such occurrence, the device internal power switch is immediately turned off and the load is disconnected. removed or if thermal protection or power limit are activated. During current limit events the monitor/fault pin is set to high logic level (4.5 V typ.).
7.3 Monitor/fault pin description
goes to high logic level for about 10 μs (tf), so that the user can detect the fault. Therefore the signal goes to low logic level, the output is turned off and the auto-retry cycle starts. Table 5. Monitor signal truth table for more details.
Figure 18. Monitor signal vs. power Figure 19. Monitor signal vs. power (zoom) Table 5. Monitor signal truth table microcontroller or ADC device.
7.4 Auto-retry delay time setting
7.5 PWM mode description, masking time
Table 6. Masking time vs. RD), so to avoid false triggering during in-rush power events at each PWM signal rising value of the RD resistor, as shown in the following table, where the standard 1% resistors are used. masking time (45 µs) is achieved by using RD = 1 kΩ. monitor signal starts increasing (see Figure 7. Masking time, fault signal). current flowing to the output capacitor triggers the power limit, which would cause a premature shutdown.
7.6 Details about the start-up sequence
happen several times until the COUT is fully charged and as a result, the start-up is prolonged. masking time the device could turn off. The device then starts again after the auto-retry delay time has elapsed. and time that satisfies the needs of the application. is not used in the application). Figure 20. Start-up with PWM tied to VIN Figure 21. Start-up with EN tied to VIN activated and the masking time starts.
Table 6. Masking time vs. RD
8 Application guidelines
8.1 Power supply voltage
The device is designed and optimized to work on 12 V power rails, even if the operating supply voltage can range from 10.5 V to 18 V. The maximum accuracy of the main operating features is reached for an input voltage of 12 V, therefore the operation at lower or higher voltages implies some small variations in the characteristic performance.
8.2 Input and output capacitors
Input and output capacitors are mandatory to guarantee the device control loop stability and reduce the transient effects of stray inductances present in the input and output power paths. In fact when the STPW12 quickly interrupts the current flow due to power limit or thermal shutdown events, input inductance generates a positive voltage spike on the input pin and, at same way, the output inductance generates a negative voltage spike on the output. Such spikes might overcome the absolute maximum voltage ratings of the device and damage the device itself. To reduce the effects of such transients, CIN capacitor with a minimum value of 10 μF must be connected between the input pin and GND and placed as close as possible to the device. For the same reason, COUT capacitor has to be connected on the output port. The recommended value is 10 μF, if this is compatible with the required PWM operating frequency. When the device is supplied via a power line made of very long wires, where input inductance is higher than 3-4 μH, the input capacitance should be increased to 47 μF or more. See also next paragraph for additional information about protection.
8.3 Additional protections and layout guidelines
Recommended additional protections and methods to address the input/output voltage spikes are the following: – Minimizing inductance of the input and output tracks, by making short and well dimensioned power traces. – Using TVS diodes on the input to absorb inductive spikes. – Schottky diode on the output to absorb negative spikes (for instance the STPS2L30). – Using a ground plane to connect the GND terminal of the IC (exposed pad) to the system GND. The CS capacitor, used for the selection of the auto-retry delay time, is charged by a low 160 nA (typ.) current. To minimize the effect of noisy signals present on this PCB on the Cset pin, resulting in incorrect delay time, the capacitor should be placed as close as possible to the IC pin and GND. STPW12 Application guidelines DS12478 - Rev 1 page 15/23
9 Package information
In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark.
9.1 Power SO8 package information
Figure 22. Power SO8 package outline
Package information
DS12478 - Rev 1 page 16/23
Table 7. Power SO8 mechanical data Figure 23. Power SO8 recommended footprint
Figure 24. Power SO8 tape and reel
Revision history
Table 8. Document revision history 20-Mar-2018 1 Initial release.