LTC4230IGN datasheet(12/36 Pages) LINER

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LTC4230

4230f

HOT CIRCUIT INSERTION

When circuit boards are inserted into or removed from live

backplanes, the supply bypass capacitors can draw huge

transient currents from the backplane power bus as they

charge. The transient currents can cause permanent dam-

age to the connector pins as well as cause glitches on the

system supply, causing other boards in the system to

reset.

The LTC4230 is designed to turn a printed circuit board’s

supply voltages on and off in a controlled manner, allow-

ing the circuit board to be safely inserted or removed from

a live backplane. The device provides a system reset signal

to indicate when board supply voltage drops below a pre-

determined level, as well as a dual function fault monitor.

OUTPUT VOLTAGE MONITOR

The LTC4230 uses a 1.234V bandgap reference, precision

voltage comparators and external resistor dividers to

monitor the output supply voltages as shown in Figure 1.

The operation of the supply monitor in normal mode is il-

lustrated in Figure 2. RESET 1 pulls low during an

undervoltage lockout condition. It remains low until the end

of the soft-start cycle (second timing cycle). FB1 then

assumes control of RESET 1 status. RESET 2 and RESET 3

also pull low during undervoltage lockout. However, FB2

controls RESET 2 and FB3 controls RESET 3 status imme-

diately after clearing UVLO (Figure 2, Time Points 5 and 6).

If the voltage at FB

n drops below its reset threshold

(1.234V), the FBCOMP comparator output pulls high.

After passing through a glitch filter, RESET

n changes

state. If the voltage at FB

n increases above its reset

threshold, the FBCOMP comparator output changes state

and RESET

n pulls high.

SENSE

RSENSE

10k

VCCn

VOUT

GATE

LTC4230

GND

4230 F01

RESET

CTIMER

TIMER

CLOAD

LOGIC

TIMER

1.234V

REFERENCE

FBCOMP

µP

RESET

SHORT

LONG

VCC

ON/RESET

GND

LONG

PCB EDGE

CONNECTOR

(MALE)

BACKPLANE

CONNECTOR

(FEMALE)

–

Figure 1. Supply Voltage Monitor Block Diagram

APPLICATIO S I FOR ATIO

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