Linear Technology 1029 Manuale utente

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029

Multi Channel Power Supply Sequencer and Supervisor

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

= 25°C

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Input Supply Range

2.9 6.0 V

HVCC

Input Supply Range 7.2 12.0 16.5 V

ON Threshold Voltage

•

Rising

1.3 1.8 2.3 V

MON(TH)

Voltage Monitor Reset Threshold Voltage

VSEL=V

0.492 0.500 0.508 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

Enable Pin Voltage Output in ON State V

+4.5 V

+5.5

EN(UP)

Enable Pin Pull-Up Current Enable Pin ON, V

EN•((

CC+4)

7.5 10 12.5 uA

STMR

Sequence Timer Period, STMR C

STMR=0.022UF

161 190 220 ms

PTMR

Power Good Timer Period C

PTMR=2.2UF

7.33

8.80 10.27 s

RTMR

Reset Timer C

RTMR=0.047UF

156.7

188.0 219.3 ms

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

TPV1

TPV2

TPV3

TPV4

V1 Time Position

V2 Time Position

V3 Time Position

V4 Time Position

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029

Multi Channel Power Supply Sequencer and Supervisor

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

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

With the +5V power supply off, connect the supply to

the 5V_AUX and GND turrets

Turn the +5V supply on and then switch the ON control

signal from low to high by pressing the button S1.

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%.

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%.

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.

Change jumpers V1 (JP3), V2 (JP5), V3 (JP4), and V4

(JP6) positions from INT to EXT.

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.

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.

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029

Multi Channel Power Supply Sequencer and Supervisor

Figure 1. Demo Circuit 1029A Connections for Operation with Internal Supplies

Figure 2. Power-Up and Power-Down Transients.

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029

Multi Channel Power Supply Sequencer and Supervisor

Figure 3. Demo Circuit 1029A Connections for Operation with External Supplies

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029

Multi Channel Power Supply Sequencer and Supervisor

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029

Multi Channel Power Supply Sequencer and Supervisor

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029

Multi Channel Power Supply Sequencer and Supervisor

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029

Multi Channel Power Supply Sequencer and Supervisor

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1029

Multi Channel Power Supply Sequencer and Supervisor

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