ISL6121 Datasheet, PDF (6/16 Pages) Intersil Corporation – Single Supply Integrated Current Limiting Controller

ISL6123, ISL6124, ISL6125, ISL6126, ISL6127, ISL6128
previous GATE has reached ~VQP-1V. 160ms after the last
GATE is at VQP the RESET# output will be deasserted. Once
any UVLO is unsatisfied, RESET# is pulled low, SYSRST# is
pulled low and all GATEs are simultaneously turned off. When
ENABLE# is signaled high the D GATE will start to pull low and
once below 0.6V the next GATE will then start to pull low and so
on until all GATEs are at 0V. Unloaded, this turn off sequence
will complete in <1ms. This variant offers a lower cost and size
implementation as the external delay caps are not used. Since
the delay caps are not used this IC can not delay the start of
subsequent GATEs thus necessary stabilization or system
house keeping need to be considered.
The ISL6128 is a four channel device that groups the four
channels into two groups of two channels each, as A, B and
C, D. Each group having its own ENABLE# and RESET# I/IO
pins. This requires all four UVLO and both ENABLE#s to be
satisfied for sequencing to start. The A, B group will first turn on
10ms after the second ENABLE# is pulled low with A then B
turning on followed by C then D. Once the preceding GATE =
VQP the next DLY_ON pin starts to charge its capacitor thus
turning on all four GATEs. Approximately 160ms after D GATE
= VQP the RESET# output is released to go high. Once any
UVLO is unsatisfied, only the related group’s RESET# and two
GATEs are pulled low. The related EN input has to be cycled for
the faulted group to be turned-on again. Normal shutdown is
invoked by either signaling both ENABLE# inputs high which
will cause all the two related GATEs to shutdown in reverse
order from turn-on. DLY_X caps adjust the delay between
GATES during turn on and off but not the order.
During bias up the RESET# output is guaranteed to be in
the correct state with V_DD lower than 1V.
The SYSRST# pin is a true I/O connection having both
functions. As an input, if it is pulled low all GATEs will
unconditionally shut off and RESET# pulls low, see Figure
6. This input can be used as a no wait enabling input, if all
inputs (ENABLE & UVLO) are satisfied it does not wait
through the ~10ms enable delay to initiate DLY_ON cap
charging. It is also useful when multiple sequencers are
implemented in a design needing simultaneous shutdown
(kill switch) across all sequencers. As an output, after the
on sequence is completed it will pull low after any UVLO is
unsatisfied longer than T_FIL and pull all other SYSRST#
inputs low on common connection thus unconditionally
shutting down all outputs across multiple sequencers.
Except ISL6128 after a fault, restart of the turn on
sequence is automatic once all requirements are met. This
allows for no interaction between the sequencer and a
controller IC if desired. The ENABLE & RESET# I/O do
allow for a higher level of feedback and control if desired.
The ISL6128 requires that the related ENABLE# be cycled
for restart of its associated group GATEs.
If no capacitors are connected between DLY_ON or
DLY_OFF pins and ground then all such related GATEs
start to turn on immediately after the 10ms (T_UVLOdel)
ENABLE stabilization time out has expired and the GATEs
start to immediately turn off when ENABLE is asserted.
If some of the rails are to be sequenced together, in order to
eliminate the effect of capacitor variance on the timing and to
reduce cost, a common capacitor can be connected to two
or more DLY_ON or DLY_OFF pins. In this case multiply the
capacitor value by the number of common DLY_X pins to
retain the desired timing.
Table 1 illustrates the nominal time delay from the start of
charging to the 1.27V reference for various capacitor
values on the DLY_X pins. This table does not include the
10ms of enable lock out delay during a start up sequence
but represents the time from the end of the enable lock out
delay to the start of GATE transition. There is no enable
lock out delay for a sequence off, so this table illustrates
the delay to GATE transition from a disable signal.
TABLE 1.
NOMINAL DELAY TO SEQUENCING THRESHOLD
DLY PIN CAPACITANCE
TIME (s)
Open
0.00006
100pF
0.00013
1000pF
0.0013
0.01µF
0.013
0.1µF
0.13
1µF
1.3
10µF
13
NOTE: Nom. T_{DEL_SEQ} = Cap (µF) * 1.3MΩ.
Figure 2 illustrates the turn-on and Figure 3 the nominal turnoff
timing diagram of the ISL6123 and ISL6124 product.
The ISL6125 is similar except the open drains instead of GATE
pins are pulled up to V_DD.
Note the delay and flexible sequencing possibilities.
6
FN9005.4
June 10, 2005