LTC1647-3 Linear Technology, LTC1647-3 Datasheet - Page 13

• Manufacturer Part Number: LTC1647-3
• Description: Dual Hot Swap Controllers
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
If a dead short occurs after a supply connection is made
(Figure 12), the sense resistor R1 and the R
enhanced Q1 provide a low impedance path for nearly
unlimited current flow. The LTC1647 discharges the GATE
pin in a few microseconds, but during this discharge time
current on the order of 150 amperes flows from the V
power supply. This current spike glitches the power sup-
ply, causing V
On recovery from overload, some supplies may over-
shoot. Other devices attached to this supply may reset or
malfunction and the overshoot may also damage some
components. An inductor (1 H to 10 H) in series with
Q1’s source limits the short-circuit di/dt, thereby limiting
the peak current and the supply glitch (Figure 12c and
12d). Additional power supply bypass capacitance also
reduces the magnitude of the V
CC
to dip (Figure 12a and 12b).
U
U
CC
glitch.
W
DS(ON)
U
of fully
CC
LTC1647-1/LTC1647-2/LTC1647-3
V
The two Hot Swap channels of the LTC1647 are ideally
suited for V
Figure 13 shows an application using the LTC1647-2 on
the system side of the device bay interface (1394 PHY and/
or USB). The controller detects the presence of a periph-
eral in each device bay and controls the LTC1647-2. The
timing waveform illustrates the following sequence of
events: t1, rising out of undervoltage lockout with GATE 1
ramping up; t2, load current fault at R1; t3, circuit breaker
resets with R5/C3 delay; t4/t5, controller gates off/on
device supply with RC delay; t6, device enters undervolt-
age lockout.
If C6 is not connected in Figure 13, FAULT 2 and ON2 will
have similar waveforms. t7 initiates an ON sequence; t8, a
load fault is detected at R7 with FAULT 2 pulling low. If the
controller wants to stretch the interval between retries, it
can pull ON2 low at t9 ( t9 – t8 < 0.4•t
controller initiates a new power-up/down sequence.
ID
Power Controller
ID
power control in portable computers.
RESET
). At t10/t11, the
13