Datasheet LTM4614 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | Dual 4A per Channel Low VIN DC/DC µModule Regulator |
| Pages / Page | 20 / 10 — applicaTions inForMaTion. Power Good. COMP Pin. Figure 3. Output Voltage … |
| File Format / Size | PDF / 380 Kb |
| Document Language | English |
applicaTions inForMaTion. Power Good. COMP Pin. Figure 3. Output Voltage Coincident Tracking
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LTM4614
applicaTions inForMaTion
TRACK1 is the track ramp applied to the slave’s track pin. feedback resistor of the slave regulator in equal slew rate TRACK1 applies the track reference for the slave output up or coincident tracking, then RTA is equal to RFB with VFB = to the point of the programmed value at which TRACK1 VTRACK. Therefore RTB = 4.99k and RTA = 10k in Figure 2. proceeds beyond the 0.8V reference value. The TRACK1 Figure 3 shows the output voltage tracking waveform for pin must go beyond the 0.8V to ensure the slave output coincident tracking. has reached its final value. In ratiometric tracking, a different slew rate maybe desired Ratiometric tracking can be achieved by a few simple cal- for the slave regulator. RTB can be solved for when SR culations and the slew rate value applied to the master’s is slower than MR. Make sure that the slave supply slew TRACK pin. As mentioned above, the TRACK pin has a rate is chosen to be fast enough so that the slave output control range from 0V to 0.8V. The control ramp slew rate voltage will reach it final value before the master output. applied to the master’s TRACK pin is directly equal to the For example, MR = 2.5V/ms and SR = 1.8V/1ms. Then master’s output slew rate in Volts/Time. RTB = 6.98k. Solve for RTA to equal to 3.24k. The master The equation: output must be greater than the slave output for the MR tracking to work. Output load current must be present • 4.99k =RTB for tracking to operate properly during power down. SR where MR is the master’s output slew rate and SR is the
Power Good
slave’s output slew rate in Volts/Time. When coincident PGOOD1 and PGOOD2 are open-drain pins that can be tracking is desired, then MR and SR are equal, thus RTB used to monitor valid output voltage regulation. These is equal to 4.99k. RTA is derived from equation: pins monitor a ±7.5% window around the regulation point. 0.8V R
COMP Pin
TA = VFB V V + FB – TRACK This pin is the external compensation pin. The module 4.99k R R FB TB has already been internally compensated for all output voltages. Table 4 is provided for most application require- where VFB is the feedback voltage reference of the regula- ments. The LTpowerCAD GUI is available for other control tor, and VTRACK is 0.8V. Since RTB is equal to the 4.99k top loop optimization. MASTER OUTPUT SLAVE OUTPUT OUTPUT VOLTAGE (V) TIME 4614 F03
Figure 3. Output Voltage Coincident Tracking
4614fb 10 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Simplified Block Diagram Decoupling Requirements Operation Applications Information Package Description Revision History Package Photograph Related Parts
applicaTions inForMaTion
TRACK1 is the track ramp applied to the slave’s track pin. feedback resistor of the slave regulator in equal slew rate TRACK1 applies the track reference for the slave output up or coincident tracking, then RTA is equal to RFB with VFB = to the point of the programmed value at which TRACK1 VTRACK. Therefore RTB = 4.99k and RTA = 10k in Figure 2. proceeds beyond the 0.8V reference value. The TRACK1 Figure 3 shows the output voltage tracking waveform for pin must go beyond the 0.8V to ensure the slave output coincident tracking. has reached its final value. In ratiometric tracking, a different slew rate maybe desired Ratiometric tracking can be achieved by a few simple cal- for the slave regulator. RTB can be solved for when SR culations and the slew rate value applied to the master’s is slower than MR. Make sure that the slave supply slew TRACK pin. As mentioned above, the TRACK pin has a rate is chosen to be fast enough so that the slave output control range from 0V to 0.8V. The control ramp slew rate voltage will reach it final value before the master output. applied to the master’s TRACK pin is directly equal to the For example, MR = 2.5V/ms and SR = 1.8V/1ms. Then master’s output slew rate in Volts/Time. RTB = 6.98k. Solve for RTA to equal to 3.24k. The master The equation: output must be greater than the slave output for the MR tracking to work. Output load current must be present • 4.99k =RTB for tracking to operate properly during power down. SR where MR is the master’s output slew rate and SR is the
Power Good
slave’s output slew rate in Volts/Time. When coincident PGOOD1 and PGOOD2 are open-drain pins that can be tracking is desired, then MR and SR are equal, thus RTB used to monitor valid output voltage regulation. These is equal to 4.99k. RTA is derived from equation: pins monitor a ±7.5% window around the regulation point. 0.8V R
COMP Pin
TA = VFB V V + FB – TRACK This pin is the external compensation pin. The module 4.99k R R FB TB has already been internally compensated for all output voltages. Table 4 is provided for most application require- where VFB is the feedback voltage reference of the regula- ments. The LTpowerCAD GUI is available for other control tor, and VTRACK is 0.8V. Since RTB is equal to the 4.99k top loop optimization. MASTER OUTPUT SLAVE OUTPUT OUTPUT VOLTAGE (V) TIME 4614 F03
Figure 3. Output Voltage Coincident Tracking
4614fb 10 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Simplified Block Diagram Decoupling Requirements Operation Applications Information Package Description Revision History Package Photograph Related Parts
