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16
FN9005.8
February 5, 2007
Application Implementations
Multiple Sequencer Implementations
In order to control the sequencing of more than 4 voltages,
several of the ISL6123, ISL6124, ISL6125 or ISL6127
devices can be variously configured together to accomplish
this. There may be concerns of a particular implementation
that would make a particular configuration preferable over
another. The fundamental questions to answer to determine
which configuration is best suited for your applications are:
1. What level of voltage assurance is needed prior to
sequencing on and can the voltage supplies be grouped
into high and low criticality
2. Is there a critical maximum time window all supplies must
be present at load or is there a first and a second group
preference possibly with some work done in between the
two groups of voltages being present
Three configurations are described and illustrated here.
In applications where the integrity of critical voltages must be
assured prior to sequencing, additional monitoring of the
critical supplies is needed. If the compliance of the voltage is
critical for either undervoltage and/or overvoltage, the
ISL613X family of supervisors can be employed to provide
this additional assurance across multiple sequencers. See
document FN9115 for supervisor data sheet. Figure 17 is a
block diagram of this voltage compliant, high assurance, low
risk configuration showing the ISL613X supervisor and a mix
of FET switched outputs and logic output sequencers
(ISL6124 and ISL6125 ICs).
TABLE 3. ISL6125EVAL1 COMPONENT LISTING
COMPONENT
DESIGNATOR
COMPONENT FUNCTION
COMPONENT DESCRIPTION
U1
ISL6125
, Four Supply Sequencer
Intersil,
ISL6125,
Four Supply Sequencer with Open Drain
Outputs
R6
5V to UVLO_A Resistor for Divider String
8.45k
Ω
1%, 0402
R12
UVLO_A to GND Resistor for Divider String
1.47k
Ω
1%, 0402
R1
3.3V to UVLO_B Resistor for Divider String
7.68k
Ω
1%, 0402
R11
UVLO_B to GND Resistor for Divider String
2.26k
Ω
1%, 0402
R2
2.5V to UVLO_D Resistor for Divider String
6.98k
Ω
1%, 0402
R3
UVLO_D to GND Resistor for Divider String
3.01k
Ω
1%, 0402
R4
1.5V to UVLO_C Resistor for Divider String
4.99k
Ω
1%, 0402
R5
UVLO_D to GND Resistor for Divider String
4.99k
Ω
1%, 0402
R9
RESET LED Current Limiting Resistor
750
Ω
10%, 0805
C5
5V turn-on Delay Cap. A
DNP, 0402
C9
5V turn-off Delay Cap. A (135ms)
0.1μF 10%, 6.3V, 0402
C2
3.3V turn-on Delay Cap.B (13.7ms)
0.01μF 10%, 6.3V, 0402
C8
3.3V turn-off Delay Cap. B (13.7ms)
0.01μF 10%, 6.3V, 0402
C3
2.5V turn-on Delay Cap.D (28ms)
0.022μF 10%, 6.3V, 0402
C7
2.5V turn-off Delay Cap. D
DNP, 0402
C4
1.5V turn-on Delay Cap. C (98ms)
0.068μF 10%, 6.3V, 0402
C6
1.5V turn-off Delay Cap. C (59ms)
0.047μF 10%, 6.3V, 0402
C1
Decoupling Capacitor
0.1μF, 0805
D1
RESET#1 Indicating LED
0805, SMD LED
R8
SEQ_OUTPUT_A Pull-Up Resistor
10k
Ω
, 0402
R9
SEQ_OUTPUT_B Pull-Up Resistor
10k
Ω
, 0402
R10
SEQ_OUTPUT_C Pull-Up Resistor
10k
Ω
, 0402
R13
SEQ_OUTPUT_D Pull-Up Resistor
10k
Ω
, 0402
ISL6123, ISL6124, ISL6125, ISL6126, ISL6127, ISL6128, ISL6130