Control & Monitoring of DC-DC Buck Converters

Satish DhawanYale University

Power Distribution Working Group Meeting- Tuesday 24 February 2009 ATLAS Upgrade Week 23-27 February 2009

CERN

Do not exceed chip operating voltage. Limit by design the Absolute Maximum output of power supply – Crowbar failure rate 3% Wire melting protection in case of power shorts Commercial chips are protected for all normal faults.

Monitor voltages & Temperature & Power Good signal

Soft power on /off (?) Enable Pin Inductive Kick

3 + 3 Conditions

Inside Buck Regulator ChipPower SupplyWith Remote Sense

Vm_op = Maximum Vin operating

BY DESIGN: Vmax_Abs < Vm_op

Enable / Disable

Power Good / OK

Vout

Vmax_Abs = Absolute maximum Vout

Satish DhawanYale University23 February, 2009

SlowControl

Vout

Transient kick – with Enb/Dis with power supply Long cables on/off

One Buck per Hybrid = 20 Read out Chips

Control & Monitoring of DC-DC Buck Converters

On/Off, I, V

Temperature

Inside Buck Regulator Chip

Power Down: Low power mode. Shut output switchesOutput High side current limit pulse by pulse (turn off high side FET. After 16 times go to soft Start)Output Low side current limit pulse by pulse

(turn off low side FET) Power OK if Vout with in 10% of set voltageVout overvoltage > Disable high side FETThermal Shutdown on over temp. Restore on cool downGood thermal contact to PCB for heat removalProduce 5V with a LDO from higher voltageCurrent monitor 1000:1 Sense FET or 100 mV Resistor shunt Under voltage Input protectionSlow Turn on but NO SLOW TURN OFF- Inductive Kick ???

Chip Temperature Output is not implemented

From CMS ECAL Powering

Maximum Vout from Power Supply by Design (and not protection Circuits) =< 12 volts

LHC 4913 LDO Specifications maximum operating voltage = 12 volts Absolute maximum voltage = 14 volts spikes of ~msec

6.3 Volt 64 Amps Power supplies located 30 meters away. 4.3 Volts @ 1 to 4 Junction Box Feed 4 LVR (Low Voltage Regulator Cards – one Trigger Tower). Maximum Vout from Power Supply by Design (and not protection Circuits) =< 12 volts

Damage to LHC 4913 when power supply output reaches upper rail of 18 /20 volts 4.3 Volts @ 1 to 4 Junction Box Feed 4 LVR (Low Voltage Regulator Cards – one Trigger Tower). Maximum Vout from Power Supply by Design (and not protection Circuits) =< 12 volts

Short Circuit Current Protection

END

Regulator from Token Ring Link Board

ST Regulator L4913 Data Sheet Maximum Input Operating Voltage = 12 volts Absolute Maximum Input Voltage = 14 volts

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 14V as DC Input Voltage limit. This means that the device can withstand till 14V just for few instants, seconds or even minutes if no further stress are applied; on the contrary 12V 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 14V 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.

Email explanation from ST

With Over Voltage, ST Regulators can open Circuit >>> Isolating 0.25 µM Electronics

OR Short Circuit >>> Damage 0.25 µM Electronics

11- L4913

1.32 mAmps

LVR Board

Gnd

R1319.1K

R146.04K

DCU Input

R310KR19

10 Ώ

4.3 Vanalog4.3 Vdig

Distribution Box

GND

GNDGND

Same as Above

Same as Above

Same as Above

-S+

S-

+

100

100

100

100

510

510

510

510

PowerSupply

D

A

B

C

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. DhawanYale University

22 February, 2005

Locate in or near Power Supply

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 mAmps For 11 Regulators= 1.32 mAmps

LVR Board INHIBIT Control

Inhibit

Inhibit Return

1 Volt Drop0.1 Volt Drop

AWG # 30 wire