Download Yale University Power Distribution Working Group Meeting

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
 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
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
Enable / Disable
Slow
Control
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
Power Down: Low power mode. Shut output switches
Output 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 voltage
Vout overvoltage > Disable high side FET
Thermal Shutdown on over temp. Restore on cool down
Good thermal contact to PCB for heat removal
Produce 5V with a LDO from higher voltage
Current monitor 1000:1 Sense FET or 100 mV Resistor shunt
 Under voltage Input protection
Slow Turn on but NO SLOW TURN OFF- Inductive Kick ???
Chip Temperature Output is not implemented
From CMS ECAL Powering

LHC 4913 LDO Specifications
 maximum operating voltage = 12 volts
 Absolute maximum voltage = 14 volts spikes of ~msec
 Maximum Vout from Power Supply by Design (and not protection Circuits) =< 12 volts
Short Circuit Current Protection
 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
END
Regulator from
Token Ring Link Board
ST Regulator L4913 Data Sheet
 Maximum Input Operating Voltage = 12 volts
 Absolute Maximum Input Voltage = 14 volts
Email explanation from ST
Angelo Alberto MESSINA [[email protected] 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.
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 GND
4.3 Vdig
4.3 Vanalog
S+
S-
LVR Board
-
11- L4913
AWG # 30 wire
Inhibit
100
Inhibit Return
100
R13
19.1K
R19
10 Ώ
R3
10K
100
Gnd
1.32 mAmps
R14
6.04K
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 mAmps
For 11 Regulators= 1.32 mAmps
A
B
C
D
510
Same as Above
510
510
Same as Above
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