RBBA3000-50 High current, non-isolated DC/DC converter
2023. 5. 25
The RBBA3000-50 is a high-current (50A) intelligent buck–boost converter based on an internal digital signal processor.
1. Description
The RBBA3000-50 is a high-current (50A) intelligent buck–boost converter based on an internal digital signal processor. The use of a dedicated DSP controller allows additional features to be implemented, making this product especially useful in many practical power supply applications, including purely analog power supplies. Besides a very fast response to transient loads, the DSP core also supports a comprehensive set of output protections including short circuit, adjustable output current limit, over-voltage fault protection, and over-temperature protection.
The input voltage range is from 9V to 60VDC with a 100ms surge withstand capability of up to 80VDC. This extensive input voltage range makes the RBBA3000-50 advantageous for battery-powered systems based on lead-acid or lithium-Ion battery packs in which the charger supply voltage can surge if the battery load is disconnected suddenly. The input features an under-voltage lock-out (UVLO) that disables the converter if the input is below 6V (typ.).
There is a growing trend away from using AC uninterruptible power supplies (UPS) and towards DC backed-up supplies for ensuring functionality during a power outage. The usage of an AC supply to charge a battery or supercapacitor energy storage device and then using that stored energy to deliver AC to power the application in an emergency is very inefficient for ensuring supply continuity. The power losses in the DC charging circuit and the following AC inverter are significant. Thus, most UPSs can only store enough energy to run the system for a few minutes. This is sufficient for all computers to power down but rarely so for mechanical systems such as robotics or assembly machines to complete the current task and move to the resting position to allow rapid restarting when the mains power resumes. In contrast, operating the entire system with a high-current 48VDC allows direct battery back- up to be used with sufficient power to allow even heavy industrial assembly plants to reset safely. The RBBA3000-50 is an ideal component for such systems and can deliver a stable 48V output from an input voltage that is higher, equal to, or lower than 48VDC.
The converter is built into a standard half-brick case with an aluminum baseplate for efficient thermal bonding with a heatsink. With appropriate cooling, the RBBA3000-50 can be used up to full load over the entire -40°C to +85°C industrial ambient temperature range. The RBBA3000-50 datasheet includes calculation examples for the necessary power derating depending on the size of the available heatsink or the altitude of the application. Furthermore, four threaded inserts are provided to allow the converter to be securely fixed to both the PCB and the heatsink.
All power supplies must meet strict limits for radiated and conducted EMI (Electro-Magnetic Interference). The RBBA3000-50 datasheet includes suggestions for the required external EMC filtering to meet the EN55032 Class A.
The input voltage range is from 9V to 60VDC with a 100ms surge withstand capability of up to 80VDC. This extensive input voltage range makes the RBBA3000-50 advantageous for battery-powered systems based on lead-acid or lithium-Ion battery packs in which the charger supply voltage can surge if the battery load is disconnected suddenly. The input features an under-voltage lock-out (UVLO) that disables the converter if the input is below 6V (typ.).
There is a growing trend away from using AC uninterruptible power supplies (UPS) and towards DC backed-up supplies for ensuring functionality during a power outage. The usage of an AC supply to charge a battery or supercapacitor energy storage device and then using that stored energy to deliver AC to power the application in an emergency is very inefficient for ensuring supply continuity. The power losses in the DC charging circuit and the following AC inverter are significant. Thus, most UPSs can only store enough energy to run the system for a few minutes. This is sufficient for all computers to power down but rarely so for mechanical systems such as robotics or assembly machines to complete the current task and move to the resting position to allow rapid restarting when the mains power resumes. In contrast, operating the entire system with a high-current 48VDC allows direct battery back- up to be used with sufficient power to allow even heavy industrial assembly plants to reset safely. The RBBA3000-50 is an ideal component for such systems and can deliver a stable 48V output from an input voltage that is higher, equal to, or lower than 48VDC.
The converter is built into a standard half-brick case with an aluminum baseplate for efficient thermal bonding with a heatsink. With appropriate cooling, the RBBA3000-50 can be used up to full load over the entire -40°C to +85°C industrial ambient temperature range. The RBBA3000-50 datasheet includes calculation examples for the necessary power derating depending on the size of the available heatsink or the altitude of the application. Furthermore, four threaded inserts are provided to allow the converter to be securely fixed to both the PCB and the heatsink.
All power supplies must meet strict limits for radiated and conducted EMI (Electro-Magnetic Interference). The RBBA3000-50 datasheet includes suggestions for the required external EMC filtering to meet the EN55032 Class A.
2. Set Output Voltage
The RBBA3000-50 has an output voltage of ~1.3V if the output voltage trim resistor or trim voltage is not connected. This is a safety feature to ensure that the high output current capability of the converter does not damage the user’s application during testing or in case of a board fault.
There are two ways to set the output voltage; via an external resistor or by an externally applied trim voltage. The trim pin is continuously monitored by the internal DSP core so the dynamic output voltage adjustment is possible. This allows, for example, the supply voltage to the application to be modified according to the load or standby status to reduce the overall power consumption.
There are two ways to set the output voltage; via an external resistor or by an externally applied trim voltage. The trim pin is continuously monitored by the internal DSP core so the dynamic output voltage adjustment is possible. This allows, for example, the supply voltage to the application to be modified according to the load or standby status to reduce the overall power consumption.
Set Output Voltage Using a Fixed Resistor
The calculation is as follows:
RTrim = Trim Resistor Value [Ω]
Voutset = Trimmed Output Voltage [V]
For example, the following commonly used output voltage trim resistors could be used.
Based on the table above, a 50kΩ potentiometer could be used to manually adjust the output voltage over the range of 12V to 60V.
Fig. 1: Vout set
Voutset = Trimmed Output Voltage [V]
For example, the following commonly used output voltage trim resistors could be used.
| Trimmed Output | Trim Resistor (E96) [KΩ] |
|---|---|
| 12 | 35.7 |
| 15 | 28.0 |
| 24 | 15.0 |
| 36 | 7.15 |
| 48 | 3.01 |
| 60 | 0.392 |
Table 1: Required Output / Trim Resistor
Based on the table above, a 50kΩ potentiometer could be used to manually adjust the output voltage over the range of 12V to 60V.
Fig. 1: Vout set
Set Output Voltage Using an External Voltage
The output Voltage of the RBBA3000-50 can also be set using an external voltage. The calculation is as follows:
VsetU = External Voltage [V]
Vout,set = Required Output Voltage [V]
Fig. 2: Vout ext. Voltage control
An internal voltage reference will pull up the trim pin to 2.5V if this pin left floating. For stability, the output voltage will react to a change in the VsetU voltage with a slope of around 100mV/ms. Therefore, although a dynamic voltage adjustment to accommodate different operating conditions is possible, the reaction time is not quick enough to perform functions such as dynamic signal envelope voltage tracking.
On the other hand, if the application were to go into standby mode and the output voltage reduced from, say, 24V to 12V to halve the power consumption, the standby and wake-up time would be very quick.
Vout,set = Required Output Voltage [V]
Fig. 2: Vout ext. Voltage control
An internal voltage reference will pull up the trim pin to 2.5V if this pin left floating. For stability, the output voltage will react to a change in the VsetU voltage with a slope of around 100mV/ms. Therefore, although a dynamic voltage adjustment to accommodate different operating conditions is possible, the reaction time is not quick enough to perform functions such as dynamic signal envelope voltage tracking.
On the other hand, if the application were to go into standby mode and the output voltage reduced from, say, 24V to 12V to halve the power consumption, the standby and wake-up time would be very quick.
3. Output current limiting (max output current)
The RBBA3000-50 has an output current limit of 55A if the Iset pin (pin #4) is not connected. Thus, if no output current limiting is required, leave the Iset pin floating.
There are two ways to set the output current limit (max output current); via an external fixed or variable resistor or an externally applied set voltage. The Iset pin is continuously monitored by the internal DSP core so dynamic output current limiting is possible. This allows, for example, the current limit to be increased to handle high start-up inrush currents and then subsequently reduced to avoid damaging the application under overload conditions. The current limiting function is the hiccup mode, so if the output is overloaded or short-circuited, the output will be switched off for some time and the converter will attempt to restart.
There are two ways to set the output current limit (max output current); via an external fixed or variable resistor or an externally applied set voltage. The Iset pin is continuously monitored by the internal DSP core so dynamic output current limiting is possible. This allows, for example, the current limit to be increased to handle high start-up inrush currents and then subsequently reduced to avoid damaging the application under overload conditions. The current limiting function is the hiccup mode, so if the output is overloaded or short-circuited, the output will be switched off for some time and the converter will attempt to restart.
Set Output Current Limit Using a Fixed Resistor
The calculation is as follows:
RIset = Current limit set resistor (Ω)
Ioutset = Required output current limit (A)
For example, the following commonly used output current limit trim resistors could be used.
Based on the table above, a 33kΩ potentiometer in series with a 2R resistor could be used to manually adjust the output current limit over the range of 48A to 10A.
Fig. 3: RBBA3000-50 output current limit setting via RIset.
Ioutset = Required output current limit (A)
For example, the following commonly used output current limit trim resistors could be used.
| Required Limit [A] | Iset Resistor (E96) [KΩ] |
|---|---|
| 10 | 1.78 |
| 20 | 4.32 |
| 30 | 8.25 |
| 40 | 15.4 |
| 50 | 31.6 |
| 55 | floating |
Table 2: Required Current Limit / Iset Resistors
Based on the table above, a 33kΩ potentiometer in series with a 2R resistor could be used to manually adjust the output current limit over the range of 48A to 10A.
Fig. 3: RBBA3000-50 output current limit setting via RIset.
Set Output Current Limit Using an External Voltage
The output current limit of the RBBA3000-50 can also be set using an external voltage.
The calculation is as follows:
VsetI = External Voltage [V]
Iout,set = Required output current limit [A]
Fig. 4: RBBA3000-50 output current limit setting via VsetI.
This feature allows DAC control of the output current limit setting for dynamic current limiting.
Fig. 5: Ioutset DAC control
An internal voltage reference will pull up the Iset pin to 3.3V (Ioutset = 55A) if the pin is left disconnected. Therefore, if no output current limiting is required, leave the Iset pin floating.
For an application example of how to use this feature to make a power-limited (constant-voltage) converter, see the next section.
The calculation is as follows:
Iout,set = Required output current limit [A]
Fig. 4: RBBA3000-50 output current limit setting via VsetI.
| Current Limit [A] | VsetI [V] |
|---|---|
| 5 | 0.25 |
| 10 | 0.5 |
| 20 | 1.0 |
| 30 | 1.5 |
| 40 | 2.0 |
| 50 | 2.5 |
| 55 | floating |
Table 3: Current Limit / VsetI
This feature allows DAC control of the output current limit setting for dynamic current limiting.
Fig. 5: Ioutset DAC control
An internal voltage reference will pull up the Iset pin to 3.3V (Ioutset = 55A) if the pin is left disconnected. Therefore, if no output current limiting is required, leave the Iset pin floating.
For an application example of how to use this feature to make a power-limited (constant-voltage) converter, see the next section.
Current Monitor
The RBBA3000-50 has a dual-function current share/current monitor pin.
For single converter applications, the pin can be used to monitor the output load. In this case, the voltage generated by the converter will correspond to the output current with a linear relationship.
Fig. 6: Imon
This useful function eliminates the need for an external shunt resistor to monitor the high-side current, thereby eliminating the disadvantages of power loss through the shunt and its variation with temperature. The associated costs of a high-current precision shunt resistor, amplifier, and current mirror are also eliminated.
Fig. 7: Current monitor cct
The Ishare output could also be used with an ADC to interface the RBBA3000-50 with a microcontroller to continuously monitor the load.
The following example demonstrates ...
For single converter applications, the pin can be used to monitor the output load. In this case, the voltage generated by the converter will correspond to the output current with a linear relationship.
Fig. 6: Imon
This useful function eliminates the need for an external shunt resistor to monitor the high-side current, thereby eliminating the disadvantages of power loss through the shunt and its variation with temperature. The associated costs of a high-current precision shunt resistor, amplifier, and current mirror are also eliminated.
Fig. 7: Current monitor cct
The Ishare output could also be used with an ADC to interface the RBBA3000-50 with a microcontroller to continuously monitor the load.
The following example demonstrates ...
4. Current share / current monitor
Current Monitor
The RBBA3000-50 has a dual-function current share/current monitor pin.
For single converter applications, the pin can be used to monitor the output load. In this case, the voltage generated by the converter will correspond to the output current with a linear relationship.
Fig. 6: Imon
This useful function eliminates the need for an external shunt resistor to monitor the high-side current, thereby eliminating the disadvantages of power loss through the shunt and its variation with temperature. The associated costs of a high-current precision shunt resistor, amplifier, and current mirror are also eliminated.
Fig. 7: Current monitor cct
The Ishare output could also be used with an ADC to interface the RBBA3000-50 with a microcontroller to continuously monitor the load.
The following example demonstrates ...
For single converter applications, the pin can be used to monitor the output load. In this case, the voltage generated by the converter will correspond to the output current with a linear relationship.
Fig. 6: Imon
This useful function eliminates the need for an external shunt resistor to monitor the high-side current, thereby eliminating the disadvantages of power loss through the shunt and its variation with temperature. The associated costs of a high-current precision shunt resistor, amplifier, and current mirror are also eliminated.
Fig. 7: Current monitor cct
The Ishare output could also be used with an ADC to interface the RBBA3000-50 with a microcontroller to continuously monitor the load.
The following example demonstrates ...
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