Linear Technology 1029 Manuale utente
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029
Multi Channel Power Supply Sequencer and Supervisor
1
DESCRIPTION
LTC2928
Demonstration circuit 1029 is for evaluating the per-
formance of the LTC2928 Multichannel Power Supply
Sequencer and Supervisor.
The LTC2928 sequences and monitors up to four
power channels in power up and power down, and it
monitors those channel outputs in the steady state,
when power goes to loads. Sequencing is accom-
plished by controlling the power supply enable inputs
or N-channel MOSFET gates with the LTC2928 control-
ling outputs. Supervisory functions include undervolt-
age and overvoltage monitoring, and capturing the
output state information in the event of a system fault.
Inherent fault detection circuitry can detect:
■
Stalled (during sequencing) supplies
■
Supplies with the output voltage not satisfying the
undervoltage or overvoltage conditions
■
System controller command errors
■
Externally commanded faults
■
Sequencing faults.
The board is populated with nineteen jumpers for se-
lection of the LTC2928 operation options and with
twelve LEDs for displaying:
■
The undervoltage status in the steady state CMP1
(D5)-CMP4 (D8)
■
The LTC2928 controlling outputs states EN1 (D1)-
EN4 (D4),
■
The state signals of the ON pin (#16), the RST# pin
(#21), the OV# pin (#20), and the FLT# pin (#19).
Design files for this circuit board are available. Call the
LTC factory.
, LTC and LT are registered trademarks of Linear
Technology Corporation. ThinSOT and PowerPath
are trademarks of Linear Technology Corporation.
PERFORMANCE SUMMARY
Specifications are at T
A
= 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
CC
V
CC
Input Supply Range
2.9 6.0 V
V
HVCC
HV
CC
Input Supply Range 7.2 12.0 16.5 V
V
ON
ON Threshold Voltage
•
V
ON
Rising
1.3 1.8 2.3 V
V
MON(TH)
Voltage Monitor Reset Threshold Voltage
VSEL=V
CC
0.492 0.500 0.508 V
V
SEQ(TH)
Sequencing Thresholds
0.67 V
MON(TH)
0.33 V
MON(TH)
0.1 V
MON(TH)
0.315
0.149
0.032
0.333
0.167
0.05
0.351
0.185
0.068
V
V
V
V
EN
Enable Pin Voltage Output in ON State V
CC
+4.5 V
CC
+5.5
V
CC
+6
I
EN(UP)
Enable Pin Pull-Up Current Enable Pin ON, V
EN•((
V
CC+4)
7.5 10 12.5 uA
t
STMR
Sequence Timer Period, STMR C
STMR=0.022UF
161 190 220 ms
t
PTMR
Power Good Timer Period C
PTMR=2.2UF
7.33
8.80 10.27 s
t
RTMR
Reset Timer C
RTMR=0.047UF
156.7
188.0 219.3 ms
V1
V2
V3
V4
V1 Internal and External Input
V2 Internal and External Input
V3 Internal and External Input
V4 Internal and External Input
2.5
1.5
1.8
3.3
V
TPV1
TPV2
TPV3
TPV4
V1 Time Position
V2 Time Position
V3 Time Position
V4 Time Position
1
3
5
7
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029
Multi Channel Power Supply Sequencer and Supervisor
2
OPERATING PRINCIPLES
A single LTC2928 can control four positive supplies or
three positive and one negative.
Each supply timing position in the sequence can be any
one of the eight available time positions. Refer to the
data sheet for the external resistor values for setting the
sequence time position.
Power is applied to the LTC2928 through either the Vcc
pin (2.9V to 6V) or the HVcc pin (7.2V to 16.5V).
Each one of the four enable outputs (EN1, EN2, EN3,
EN4) provides a (Vcc+4.5)V signal to control a MOSFET
gate or a power supply enable input.
The LTC2928 monitors four supply thresholds per sup-
ply (sequence-up, sequence-down, undervoltage, over-
voltage) during a full LTC2928 operation cycle. A full
operation cycle includes two transient phases (se-
quence-up and sequence-down) and one monitor
(steady state) phase.
The time intervals between adjacent supplies’ enable or
disable signal is set by the value of the Sequence Timer
capacitor with a timing scale factor of 8670ms/uF. The
sequencing-up interval is equal to the sequencing-down
interval.
The power good timer period defines the maximum
time needed by any input supply to reach its undervolt-
age threshold (in power-up) or drop to its sequencing-
down threshold (in power-down). This period is set by a
power good timer capacitor with a timing scale factor of
4000ms/uF.
During the sequence-up phase, supply monitor inputs
are expected to cross their sequence-up threshold
(which may be different from their undervoltage thresh-
old). Any supply monitor input failing to cross its se-
quence-up threshold will stall the process and a se-
quence-up fault is generated.
During the sequence-down phase, supply monitor in-
puts are expected to cross their sequence-down
threshold (which can be different from their undervolt-
age threshold) within the selected power good time.
Any supply monitor input failing to cross its sequence-
down threshold will stall the process and generate a
sequence-down fault.
Refer to the LTC2928 data sheet for sequencing thresh-
old selection by biasing the SQT1 and SQT2 pins.
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029
Multi Channel Power Supply Sequencer and Supervisor
3
QUICK START PROCEDURE
For fast evaluation of LTC2928 performance, the board
contains four low drop out regulators (LDO): LT1761ES-
2.5, LT1761ES-1.5, LT1761ES-1.8, LT1761ES-3.3, and a
push button with control circuitry for ON control signal
generation. LDO outputs are +2.5V, +1.5V, 1.8V, and
+3.3V. Each LDO has an enable input, and works as a
power supply.
Demonstration circuit 1029 is easy to set up to evaluate
the performance of the LTC2928 with the on-board sup-
plies. Refer to the Figure 1 for the proper circuit connec-
tion. For the load resistors R1, R2, R3, and R4 use 51
Ohm 1W resistors. Connect four scope probes to the load
resistors R1, R2, R3, and R4.
Place jumpers in the following positions:
JP1 (OPERATION) LAST
JP2 (ON) INT_ON
JP3 (V1) INT
JP4 (V3) INT
JP5 (V2) INT
JP6 (V4) INT
JP7 (SQT1) GND
JP8 (VSEL) ALL POSITIVE
JP9 (RT1 Control) TIME POSITION
JP10 (SQT2) GND
JP11 (V1 POLARITY) V1_POS
JP12 (MS1) GND
JP13 (RT2 Control) TIME POSITION
JP14 (OVA CONFIG) Up•32%32%
JP15 (MS2) GND
JP16 (RT3 Control) TIME POSITION
JP17 (VIN FOR VCC) LOW VCC
JP18 (RDIS) OPEN
JP19 (RT4 Control) TIME POSITION
1.
With the +5V power supply off, connect the supply to
the 5V_AUX and GND turrets
.
2.
Turn the +5V supply on and then switch the ON control
signal from low to high by pressing the button S1.
3.
The power-up output voltages should correlate with the
transient shown in Figure 2 (Power-up phase). Accept-
able tolerance in the sequence timing is ±20%.
4.
Press the button PB (S1) to change the ON signal from
high to low and observe the output voltages. The
power-down output voltages should correlate with the
transient shown in Figure 2. (Power-down phase). Ac-
ceptable tolerance in the sequence timing is ±20%.
5.
Turn the +5V power supply off and connect four exter-
nal power supply terminals with DC1029 as shown in
Figure 3. Use external power supplies with output volt-
ages +2.5V, +1.5V, +1.8V, and +3.3V. Leave output
loads as in previous experiments or replace them with
3W resistors 2.5 Ohm. 1.5 Ohm, 2 Ohm, and 3 Ohm
accordingly to have current in each rail around 1A.
6.
Change jumpers V1 (JP3), V2 (JP5), V3 (JP4), and V4
(JP6) positions from INT to EXT.
7.
Turn all five power supplies on. Pushing the button PB
(S1) changes the ON signal from low to high and after
the power up transient completes, press PB (S1) sec-
ond time to initiate the power down. The output voltage
sequence timing should be similar to the timing with
the internal power supplies.
8.
The DC1029A could be used for the original customer
design. Based on the sequence timing and threshold
parameters define all the optional components’ values,
replace them on the board and verify design perform-
ance. Contact LTC Field Applications Engineers to get
help in designing or verifying your circuit with special
tools.
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