SMH4814 Datasheet, PDF (18/44 Pages) Summit Microelectronics, Inc. – Dual Feed Active-ORing Programmable Hot Swap Controller

SMH4814
Preliminary Information
APPLICATIONS INFORMATION (CONTINUED)
In the case when Current Regulation is enabled and
CBSENSE exceeds V_QCB before the circuitry has time
to modulate VGATE_HS, the Quick-Trip circuit assists
the modulation by pulling down on the gate
immediately. Rather than pull all the way to VSS, the
Quick-Trip circuitry may also be configured to only pull
down to within one, two or three diode of VSS
(R05[7:6]). Once CBSENSE falls back below V_QCB,
the pull-down circuitry will shut off. By this point, the
Current Regulation circuit will have had time to
activate, and VGATE_HS will be modulated to keep
the CBSENSE level at V_CR. Figure 11 and Figure 12
illustrate the current regulation function.
V_QCB
<t_PCR
CBSENSE
0V
12V
VGATE_HS
V_CR
V_CB
t_CBD
Resetting FAULT#
When the circuit breaker trips and, in the case in which
current regulation is enabled, t_PCR times out, the
VGATE_HS and PUP outputs are turned off and
FAULT# is driven low. Other events may also be
configured to cause a Fault, as determined by
R0D[3:0] and R10[7:4]. Once a Fault has occurred,
the SMH4814 may be configured (using R05[2]) to
either restart on its own after a programmable cooling
off period of t_CYC (Figure 13), or it may be configured to
stay latched off until the Fault is manually reset (Figure
14). The duty cycle timeout period t_CYC is set using
R03[7:4] and can range from 7ms to 21.5s. The Fault
condition may be manually reset by driving RESET#
low, or through the use of the Command Register.
CBSENSE
t_CBD
V_CB
t_CBD
t_CYC
VGATE_HS
0V
Figure 11 - Current Regulation With Recovery
V_QCB
CBSENSE
0V
t_PCR
V_CR
V_CB
Figure 13 - Circuit Breaker Duty Cycle Operation
with RESET# High
t_CBD
V_CB
CBSENSE
12V
VGATE_HS
t_PDD
VGATE_HS
0V
Figure 12 - Current Regulation Without Recovery
t_CBRST
RESET#
Figure 14 - Circuit Breaker Reset with RESET#
Summit Microelectronics, Inc
2080 2.0 07/21/05
18