LTC2932 Linear Technology, LTC2932 Datasheet - Page 12

• Manufacturer Part Number: LTC2932
• Description: Confi gurable Six Supply Monitor
• Manufacturer: Linear Technology

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APPLICATIONS INFORMATION
LTC2932
12
Six Supply Monitor with Hysteresis
The LTC2932 monitors six supply voltages in Figure 5 and
is confi gured to mode 6 (see Table 1). Supply tolerance
inputs T0 and T1 are tied to RST. As the LTC2932 powers
up, RST is low, which keeps the tolerance at 5%. After all
six inputs exceed their 5% threshold voltages, RST pulls
high. This changes the supply tolerance to 12.5%. If any of
the input voltages drop below the 12.5% threshold level,
reset is asserted. The push button on V6 also allows for
a manual reset when pressed.
Five Supply Power-up Sequencer
In Figure 6, the LTC2932’s real-time COMP outputs are
used to enable DC/DC converters sequentially. The system
is powered by a 12V source.
The system is started when the push-button is pressed and
the LTC2950-1 brings the RUN pin of the LTM4600 high.
Subsequently, the LTM4600 generates a 5V output which
applies power to each of the 4 DC/DC converters.
5V
3.3V
2.5V
1.8V
12V
1.2V
PUSHBUTTON
*OPTIONAL FOR EXTENDED ESD TOLERANCE
124k 1%
2150k 1%
10k*
100k
1%
100k
1%
0.1μF
Figure 5. Six Supply Monitor with Hysteresis
40.2k
12.5% Tolerance (After RST Goes High)
59k
1%
1%
R1
R2
5% Tolerance (Supplies Rising)
V1
V2
V3
V4
V5
V6
VREF
VPG
GND CRT
LTC2932
The LTC2932 is confi gured to mode 13 and a 12.5%
threshold (see Tables 1 and 2). When the threshold is
reached on V1, COMP1 pulls high. COMP1 then enables
the 3.3V converter fi rst. When the threshold is reached
on V2, COMP2 pulls high and enables the 1.8V converter
next. When all the converters have been enabled and are
good, COMP5 pulls high. RST pulls high 9.4ms after
COMP5. Figure 7 shows the power-up sequence of the
fi ve supplies and the DONE and RST outputs.
If the KILL input on the LTC2950-1 does not receive a logic
high from the RST output within 512ms of initial power-up,
EN pulls low and the LTM4600 is powered down.
In the event that the external 12V supply drops below 9.6V,
COMP6 and RST pull low. The LTC2950-1 then receives
a logic low on the KILL input, which powers down the
LTM4600 and the sequencing circuit.
C
47nF
t
RST
RT
COMP1
COMP2
COMP3
COMP4
COMP5
COMP6
RDIS
= 94ms
RST
T0
T1
10k
10k
10k
10k
10k
10k
10k
SYSTEM
LOGIC
2932 F05
2932fb