Control Monitoring of DCDC Buck Converters Satish Dhawan
Control & Monitoring of DC-DC Buck Converters Satish Dhawan Yale University Power Distribution Working Group Meeting- Tuesday 24 February 2009 ATLAS Upgrade Week 23 -27 February 2009 CERN
3 + 3 Conditions v Do not exceed chip operating voltage. v Limit by design the Absolute Maximum output of power supply – Crowbar failure rate 3% v Wire melting protection in case of power shorts üCommercial chips are protected for all normal faults. üMonitor voltages & Temperature & Power Good signal üSoft power on /off (? ) Enable Pin Inductive Kick
Transient kick – with Enb/Dis with power supply Long cables on/off Vmax_Abs = Absolute maximum Vout Vm_op = Maximum Vin operating Inside Buck Regulator Chip Power Supply With Remote Sense On/Off, I, V Slow Control Enable / Disable Power Good / OK Vout Temperature BY DESIGN: Vmax_Abs < Vm_op Satish Dhawan Yale University 23 February, 2009 One Buck per Hybrid = 20 Read out Chips Control & Monitoring of DC-DC Buck Converters Vout
Inside Buck Regulator Chip üPower Down: Low power mode. Shut output switches üOutput High side current limit pulse by pulse (turn off high side FET. After 16 times go to soft Start) üOutput Low side current limit pulse by pulse (turn off low side FET) ü Power OK if Vout with in 10% of set voltage üVout overvoltage > Disable high side FET üThermal Shutdown on over temp. Restore on cool down üGood thermal contact to PCB for heat removal üProduce 5 V with a LDO from higher voltage üCurrent monitor 1000: 1 Sense FET or 100 m. V Resistor shunt ü Under voltage Input protection üSlow Turn on but NO SLOW TURN OFF- Inductive Kick ? ? ? Chip Temperature Output is not implemented
From CMS ECAL Powering v LHC 4913 LDO Specifications v maximum operating voltage = 12 volts v Absolute maximum voltage = 14 volts spikes of ~msec v Maximum Vout from Power Supply by Design (and not protection Circuits) =< 12 volts Short Circuit Current Protection v 6. 3 Volt 64 Amps Power supplies located 30 meters away. v 4. 3 Volts @ 1 to 4 Junction Box v Feed 4 LVR (Low Voltage Regulator Cards – one Trigger Tower). v. Maximum Vout from Power Supply by Design (and not protection Circuits) =< 12 volts v Damage to LHC 4913 when power supply output reaches upper rail of 18 /20 volts v 4. 3 Volts @ 1 to 4 Junction Box v Feed 4 LVR (Low Voltage Regulator Cards – one Trigger Tower). v. Maximum Vout from Power Supply by Design (and not protection Circuits) =< 12 volts
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Regulator from Token Ring Link Board
ST Regulator L 4913 Data Sheet Ø Maximum Input Operating Voltage = 12 volts Ø Absolute Maximum Input Voltage = 14 volts Email explanation from ST Angelo Alberto MESSINA [angelo. messina@st. com Wed 6/23/2004 2: 47 PM in the ABSOLUTE MAXIMUM RATINGS table in the datasheet we indicate 14 V as DC Input Voltage limit. This means that the device can withstand till 14 V just for few instants, seconds or even minutes if no further stress are applied; on the contrary 12 V is the operative limit. Therefore if the power supply exceeds the output voltage to greater then 14 volts it can damage the regulator for sure. On the other hand in case of 14 V sporadic and short spikes the device is internally protected. The question is if your application complies with datasheet recommendations. This because any behavior out of specification, that can occur following the datasheet recommendations, has to be considered as a possible ST failure and has to be managed formally by issuing a F. A. R. (Failure Analysis Request). This F. A. R. has to be request by C. E. R. N. since we need to analyze the damaged parts on a customer report basis. With Over Voltage, ST Regulators can open Circuit >>> Isolating 0. 25 µM Electronics OR Short Circuit >>> Damage 0. 25 µM Electronics
Distribution Box Power Supply 0. 1 Volt Drop GND + GND S+ S- 4. 3 Vdig 4. 3 Vanalog LVR Board - 11 - L 4913 AWG # 30 wire Inhibit 100 Inhibit Return 100 R 19 10 Ώ 100 R 3 10 K Gnd R 13 19. 1 K 1. 32 m. Amps R 14 6. 04 K DCU Input 100 Maximum Voltage applied to Inhibit Input = 0. 5 V higher then the Power supply Pin (There is a Diode to Vcc Protection in the chip) Inhibit Input Current @ 5 V for one Regulator= 0. 12 m. Amps For 11 Regulators= 1. 32 m. Amps A B C D 510 Same as Above Locate in or near Power Supply Bits to be changed by CAN Bus Controller in sequential commands. Only one bit to be changed at one time. This is to limit the Ldi/dt voltage spike on turn off S. Dhawan Yale University 22 February, 2005 LVR Board INHIBIT Control
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