MAX4370 Datasheet, PDF (13/16 Pages) Maxim Integrated Products – Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection

Current-Regulating Hot-Swap Controller with
DualSpeed/BiLevel Fault Protection
1000
100 ^{tCSPD (ms) = 0.2 · CSPD (nF)}
10
1
0.1
V_REF
R1
ON
NTC
R2
0.6V
LOGIC
CONTROL
0.01
0.01 0.1
1
10
C_SPD (nF)
100 1000
Figure 8. Slow Comparator Response Time vs. C_SPD
R1 = R2 · (V_REF / O.6 - 1)
R2 = VALUE OF THE NTC RESISTOR AT THE LIMIT TEMPERATURE
V_REF = ANY REFERENCE VOLTAGE AVAILABLE OR V_IN
Figure 9. Temperature Monitoring and Protection
The actual turn-on time is determined by the longer of
the two timings of Case A and Case B. Set the start-up
timer (t_START) at 2 · t_ON or longer to guarantee enough
time for the output voltage to settle; also take into con-
sideration device parameter variation.
Slow Comparator Response Time (C_SPD)
The slow comparator threshold is set at 50mV, and its
response time is determined by the external capacitor
connected to CSPD (Figure 8).
A minimum response time of 20µs (typ) is achieved by
leaving this pin floating. This time is determined inter-
nally and is not affected by stray capacitance at CSPD
(up to 100pF).
Set the slow comparator response time to be longer
than the normal operation load transients.
ON Comparator
The ON/OFF function of the MAX4370 is controlled by
the ON comparator. This is a precision voltage com-
parator that can be used for temperature monitoring
(Figure 9) or as an additional undervoltage lockout. The
comparator threshold voltage is set at 0.6V with a 3mV
typical hysteresis.
The ON comparator initiates start-up when its input volt-
age (V_ON) rises above the threshold voltage, and turns
off the MOSFET when the voltage falls below the
threshold. The ON comparator is also used to reset the
MAX4370 after a fault condition.
The ON comparator input and the STAT output can be
pulled to voltages up to 14V independently of V_IN.
REMOVABLE
BACKPLANE CARD
V_CC
10k
V_IN
VSEN GATE
MAX4370
ON
RESET
1M
Figure 10. Fail-Safe Connector
In some applications, it is useful to use connectors with
staggered leads. In Figure 10, the ON pin forces the
removable board to be powered up only when all con-
nections are made.
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