Product # IQ65033QGA12

Phone 1-888-567-9596

www.synqor.com

Doc.# 005-0006070 Rev. B

09/06/2012

Page 11

Outputs:

Current:

Package:

5.0V/ 3.3V

10A

Quarter-brick

Application Section

EXTERNAL HOLD-UP CAPACITOR SELECTION

C

tolerance):

C

2t

Equation A

2

U

Typically a strong function of VH (see Figure E).

The ATCA specification requirement is 8.70ms (see Figure F).

Where:

V

H

= hold-up capacitor charge voltage.

V

U

= minimum operating voltage on the 48V output; the greater

of the under-voltage lockout threshold of the payload power

converter, and the under-voltage lockout threshold of the

management power converter.

t

U

= time from when the highest input feed voltage drops below

V

above V

V

F

= voltage at which the hold-up capacitor is engaged.

P

H

= power drawn from the hold-up capacitor, the sum of the input

power of the payload power converter, and the input power

of the 3.3V mgmt power converter (see Figure 9):

P

P

out 12V

+ P

IN 3.3V

Equation A

η

12V

P

out12V

= output power delivered by the payload converter.

η

12V

= efficiency of the 12V payload converter.

P

IN 3.3V

= output power delivered by the payload converter.

EXTERNAL HOLD-UP CAPACITOR VOLTAGE RATING

Operating electrolytic capacitors near their voltage rating does not

significantly affect their reliability, as it does with tantalum or ceramic

type capacitors. The operating life of electrolytic capacitors is primarily

determined by the capacitor internal temperature. The capacitor lifetime

roughly doubles for every 10ºC reduction in internal temperature. SynQor

recommends running 100V rated electrolytic capacitors at 90V, which

dramatically increases hold-up time for a given capacitor volume (see

Figure E). A built-in circuit automatically discharges the hold-up capacitor

when the input voltage is removed.

36.0V

43.0V

41.0V

0

10

20

30

40

50

60

70

80

90

100

0

1

2

3

4

5

6

7

8

9

10

Time (ms)

8.70ms

Fuse-Blowing type transient that cause a drop

in both input feeds simultaneously.

Figure F: The PICMG 3.0 R2.0 AdvancedTCA Base Specification requires

continuous operation through a zero-volt transient, lasting 5ms (Section

4.1.2.2). However, this is not a square wave: the voltage starts at a minimum

amplitude of -43V, falls at 50V/ms, remains at 0V for 5ms, and then rises at

12.5V/ms. At the worst case values of the hold-up connect threshold and the

management power under-voltage lockout threshold, the required hold-up time

is 8.70ms

1000

10000

100000

50

60

70

80

90

100

Hold-up Charge Voltage (V)

Figure G: Plot of Equation C, used to choose the external trim resistor value

based on the desired Hold-up Capacitor charge voltage. Error bars indicate

the worst case range of charge voltage for a given external trim resistor

value (assumes 1%, 100ppm for external trim resistor tolerance). Worst case

calculation over temp range -40ºC to 125ºC.

EXTERNAL HOLD-UP TRIM RESISTOR SELECTION

R

up capacitor charge voltage (V

R

(

500,000

- 10,000

Equation C

V

HU - 50.0