LTC4211 Ver la hoja de datos (PDF) - Linear Technology

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LTC4211

Hot Swap Controller with Multifunction Current Control

Linear Technology 

LTC4211

PIN FUNCTIONS (8-Lead Package/10-Lead Package)

clamps at the GATE pin determine the gate drive voltage

(ΔVGATE = VGATE – VCC). The charge pump produces a

minimum 4.5V of ΔVGATE for supplies in the range of 2.7V

≤ VCC < 4.75V. For 4.75V ≤ VCC ≤ 12V the ΔVGATE is limited

by zener clamp Z1 connected between the GATE and VCC

pins. The ΔVGATE is typically at 12V and with guaranteed

minimum value of 10V. For VCC > 12V, the Zener clamp

Z2 begins to set the limitation for ΔVGATE. Z2 clamps the

gate voltage to ground to 26V typically. The minimum Z2’s

clamp voltage is 23V. This effectively sets ΔVGATE to 8V

minimum at VCC = 15V.

SENSE (Pin 7/Pin 8): Circuit Breaker Set Pin. With a sense

resistor placed in the power path between VCC and SENSE,

the LTC4211’s electronic circuit breaker trips if the voltage

across the sense resistor exceeds the thresholds set inter-

nally for the SLOW COMP and the FAST COMP, as shown

in the Block Diagram. The threshold for the SLOW COMP is

VCB(SLOW) = 50mV, and the electronic circuit breaker trips

if the voltage across the sense resistor exceeds 50mV for

20μs. The SLOW COMP delay is fixed in the S8/MS8 ver-

sion and adjustable in the MS version of the LTC4211. To

adjust the SLOW COMP’s delay, please refer to the section

on Adjusting SLOW COMP’s Response Time.

Under transient conditions where large step current

changes can and do occur over shorter periods of time,

a second (fast) comparator instead trips the electronic

circuit breaker. The threshold for the FAST COMP is set at

VCB(FAST) = 150mV, and the circuit breaker trips if the

voltage across the sense resistor exceeds 150mV for

more than 300ns. The FAST COMP’s delay is fixed in the

LTC4211 and cannot be adjusted. To disable the electronic

circuit breaker, connect the VCC and SENSE pins together.

VCC (Pin 8/Pin 9): This is the positive supply input to

the LTC4211. The LTC4211 operates from 2.5V < VCC <

16.5V, and the supply current is typically 1mA. An internal

undervoltage lockout circuit disables the device until the

voltage at VCC exceeds 2.3V.

FAULT (Not available on S8/MS8, Pin 10 MS): FAULT is

both an input and an output. Connected to this pin are an

analog comparator (COMP6) and an open-drain N-channel

FET. During normal operation, if COMP6 is driven below

1.236V, the electronic circuit breaker trips and the GATE

pin pulls low. Typically, a 10k pull-up resistor connects

to the FAULT pin. This pull-up is required to allow the

LTC4211 to begin a second timing cycle (VFAULT > 1.286)

and start-up properly. This also allows the use of the

FAULT pin as a status output. Under normal operating

conditions, the FAULT output is a logic high. Two condi-

tions cause an active low on FAULT: (1) the LTC4211’s

electronic circuit breaker trips because of an output short

circuit causing a fast output overcurrent transient (FAST

COMP trips circuit breaker); or (2) VFILTER > 1.236V. The

FAULT output is driven to logic low and is latched logic

low until the ON pin is driven to logic low for 150μs (the

tRESET duration).

FILTER (Not available S8/MS8, Pin 3 MS): Overcurrent

Fault Timing Pin and Overvoltage Fault Set pin. With a

capacitor connected from this pin to ground, the SLOW

COMP’s response time can be adjusted. In the S8/MS8

version of the LTC4211, the FILTER pin is not available

and the delay time from overcurrent detect to GATE OFF

is fixed at 20μs.

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