DC998A - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 998A
NEGATIVE HOT SWAP CONTROLLER WITH ADC AND I2C MONITORING
LTC4261CGN
DESCRIPTION
Demonstration Circuit 998A showcases the
LTC®4261 negative Hot Swap controller with ADC
and I2C monitoring in a 200W, 36 to 72V application.
Included on board is isolation for power good control
pins and the single wire interface output. LEDs indicate the presence of -48V input and output, as well as
the state of numerous I/O pins. Jumpers allow maximum flexibility in examining the many features of the
LTC4261.
The -48V input, RTN and -48V output are separated
from each other by at least 55 mils spacing. Input and
output connections are made by 93 mil turrets which
if removed, accommodate insertion of up to 12 gauge
wires for in-situ testing.
Design files for this circuit board are available. Call
the LTC factory.
LTC is a registered trademark of Linear Technology Corporation
Table 1. Performance Summary (TA = 25°C)
SYMBOL
MIN
TYP
MAX
UV ON
42.5
43
43.5
V
-48V
UV OFF
37.5
38.5
39.5
V
INPUT
OV OFF
77
V
OV ON
68
V
IOUT, CB
PARAMETER
CONDITION
CIRCUIT BREAKER TRIP CURRENT
5.5
6.25
7
UNITS
A
OPERATING PRINCIPLES
The top of the board contains the components germane to a typical application, along with indicating
LEDs, connection turrets, and jumpers to configure
various features and I/O pins. The 93-mil turrets are
not swaged and may be removed for attachment of
up to 12 gauge wire. The board can deliver 200W
over the full operating range.
The bottom of the board contains components not
associated with the LTC4261 typical application, such
as optional I2C bus monitoring, scaling resistors for
the A/D inputs, and protection resistors to make the
demo circuit more resistant to careless mistakes in a
bench-testing environment. Two important components are located on the bottom of the board; bypass
capacitors for INTVCC and VIN are placed there to
achieve short, direct path.
Clamps on the input and output prevent avalanche in
the MOSFET.
Changing Current Levels
The board may be modified for other current levels.
The LTC4261 current sense voltage range is 45 to
55mV, and space is provided for up to three, 1W
sense resistors corresponding to a current of about
50A. Copper loss is about 1.2 milliohms, equivalent
to about 2 squares of 1-ounce copper; this excludes
MOSFET and sense resistor losses.
A clear line of demarcation separates RTN, -48V
INPUT, and -48V OUTPUT, with a spacing of at least
55 mils to any adjacent trace. Since the LTC4261
uses a shunt regulated supply, there is no high voltage present across any package pins. DRAIN con-
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 998A
NEGATIVE HOT SWAP CONTROLLER WITH ADC AND I2C MONITORING
nects to the output through RD, which serves to
block the high voltage sometimes present there.
RAMP reaches the output through capacitor, CR.
Similarly, RIN1-3 stand off high voltage at RTN.
Although PGIO and PG# are designed to withstand
100V, they lack 55 mil spacing to adjacent package
pins. Nevertheless, care has been taken to situate
these pins at one corner of the package, and EN# has
been placed as a guard to minimize leakage issues
into surrounding circuitry. In addition if flashover occurs, PGIO and PG# are used with series resistors (in
this case 24 kohms) which limit the flow of current
and readily stand off the operating voltage and any
transients.
Jumpers
DC998A contains 11 jumpers, and a 14-pin connector
for I2C interface (discussed later in the I2C Interface
section). The jumpers either configure a pin or provide a means for bringing the associated pin out to a
turret for external connections. A description of each
jumper follows. The purpose of this section is not to
replicate the data sheet. For further details refer to
that document.
JP10 and JP4, I2C Address ADR0 and ADR1. These
jumpers program the I2C address for the board. The
address pins ADR0 and ADR1 are 3-state inputs; they
can be LOW (VEE), OPEN, or HIGH (INTVCC). The
default stuffing is low-low, which corresponds to a
device write address of 0010000 (20h). An address of
ADR0=low and ADR1=high puts the LTC4261 in Single-Wire Broadcast Mode, and free-running serial
data appears at "Single Wire Interface" (connect a
separate, 5V supply to power opto U2).
JP8, ON. Selects between forcing the ON pin HIGH
(INTVCC), LOW (VEE), or EXT, which passes the pin
through to the adjacent ON turret. The default is
ON=high, which allows the part to turn on independent of I2C control.
J1, I2C INTERFACE. See separate section covering
this topic.
JP7, SDA. The LTC4261 has a split SDA function,
appearing as the SDAI (input) and SDAO (output)
pins. These two pins facilitate optical isolation. JP7 is
initially jumpered in the COM (common) position,
which shorts SDAI and SDAO together and allows the
board to operate with DC590A. If JP4 is moved to the
SPLIT position, these pins are separated.
JP3, INTERFACE. Selects between I2C and SINGLE
WIRE interface modes. This jumper moves SDAO between JP3 (I2C) and the HCPL-0300 optical isolator.
JP2, EN#. Connects EN# HIGH (INTVCC, disable),
LOW (VEE, enable), or EXT (adjacent turret). Default
is low to enable the LTC4261 on power up.
JP5, UV/OV. Connects top of UV and OV dividers to
RTN or adjacent SHORT PIN turret. Default is RTN.
JP1, PGIO. PGIO pin has three possible functions; it
can be an I2C programmable open collector output, a
logic input read by I2C or (the default) a power good
output. JP1 gives the choice of connecting PGIO to
an opto isolator (OPTO, default jumper position), or
to the PGIO turret (EXT).
JP6, PGI#. The LTC4261 monitors a down-stream
DC-DC converter by watching for PGI# to go low
within a timer interval during power up. If PGI# does
not go low, the LTC4261 shuts down. JP6 offers connections to an opto isolator (OPTO) or connects PGI#
to VEE (BYPASS). BYPASS is the default jumper position, which ignores the state of the opto isolator.
JP9, ADIN. Moves ADIN between the ADIN turret
(EXT) and a divider to the -48V output (default) which
measures VDS.
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 998A
NEGATIVE HOT SWAP CONTROLLER WITH ADC AND I2C MONITORING
JP11, ADIN2. Moves ADIN2 between the ADIN2 turret
(EXT) and the OV divider (default) which measures
the input voltage.
serial data stream then appears on the OUTPUT turret, between +5V and 0V.
Other Turrets
J1, I2C INTERFACE
FLTIN#. This input is available at a turret along the left
margin of the board. It is pulled up to INTVCC by a
100 kohm resistor. FLTIN# is really just a logic input
that can be read via I2C, and has no other effect on
the operation of the LTC4261.
A simple means of exercising the I2C port is provided
at J1, to be used in conjunction with a PC and
DC590A. DC590A acts as in intermediary between
DC998A and a PC, complete with optical isolation.
Simply plug in the 14-wide DC590A interface cable to
J1. The software is found on the LTC website,
www.linear.com. There is a "personality" EEPROM on
the bottom of the board which is read by DC590A and
used to automatically bring up the correct software.
From there all of the LTC4261 registers can be read
from or written to, allowing full control over all of the
device's features.
INTVCC. Allows examination of the INTVCC pin. Used
as a supply for pullups to PGI#, FLTIN#, EN#, ON,
ADR0, ADR1, ALERT#, SDAO, SDAI and SCL. Note
that the aforementioned pins are limited to
INTVCC+300mV absolute maximum. If INTVCC is
loaded, provision must be made to supply this current by increasing the bias to VIN.
If you experience trouble getting the I2C interface
running with DC590A, verify the following:
JP10=LOW, JP4=LOW, JP7=COM, and JP3=I2C. Of
course the following conditions must be met in order
for the output to turn on automatically: JP8=LOW
and JP5=RTN or SHORT PIN connected to RTN.
VEE (located close to the LTC4261). This is the
common reference and substrate for the LTC4261. If,
and only if you are using a floating bench supply and
floating load, then -48V INPUT can be made "ground"
to facilitate testing. In this case VEE serves as a quiet,
small signal ground for a scope probe.
To connect an external I2C interface, disconnect
DC590A and use J1, or use the SDAO, SDAI and SCL
turrets directly. Note that the I2C lines are referred to
VEE as a common.
VEE (located close to other turrets). These are connected to the LTC4261 VEE pin, and serve as a common reference for the adjacent turrets, such as PGIO,
ON, EN#, FLTIN#, ADIN, and ADIN2.
SINGLE WIRE INTERFACE
VIN. Allows examination of the VIN pin.
It is possible to operate the LTC4261 autonomously,
yet still retain the monitoring functions by placing it in
Single-Wire Broadcast Mode. To do this, connect
JP3=SINGLE WIRE, disconnect J1, and disconnect
any connections to the I2C turrets. Set the I2C
ADDRESS jumpers to JP4=HIGH and JP10=LOW.
PGI# INPUT. This is the LED side of a MOC207 opto
isolator (U4). Connect to the output of a downstream
dc-dc converter to detect proper power up. There is a
100 ohm resistor in series with the opto’s LED. Move
JP6 to OPTO to use this feature.
Next, turn your attention to the fully floating SINGLE
WIRE INTERFACE turrets. Connect an outboard 5V
supply to the HCPL-0300 opto isolator (+5V, 0V). A
PG# OUTPUT. This is the phototransistor side of a
MOC207 opto isolator (U3). The phototransistor turns
on when PG# goes low. The base is floating. Drive to
the opto isolator is indicated by adjacent LED D2.
3
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 998A
NEGATIVE HOT SWAP CONTROLLER WITH ADC AND I2C MONITORING
PGIO OUTPUT. This is the phototransistor side of a
MOC207 opto isolator. The phototransistor turns on
when PGIO goes low. The base is floating. Drive to
the opto isolator is indicated by adjacent LED D1.
Move JP1 to OPTO to use this feature. If JP1 is
placed in the EXT position, the PGIO pin is connected
directly to the PGIO turret.
QUICK START PROCEDURE
1.
Connect -48V to -48V INPUT, with the common
return connected to RTN. The output is taken at 48V/200W OUTPUT.
2.
The LTC4261 can be turned on by either I2C control, or by jumper selection. In either case, EN#
(JP2 or the adjacent turret) must be low before the
LTC4261 will turn on. Autonomous operation is accomplished by setting ON (JP8) high, EN# (JP2)
low, and then pulling UV/OV (JP5) to RTN. The
condition of JP1, JP3, JP4, JP6, JP7, JP9, JP10
and JP11 just don't matter as far as turn-on is
concerned. If PGI# is not pulled low before the
timeout interval, the LTC4261 will power up briefly
and then shut down. Place JP6 in the BYPASS position to avoid this behavior.
3.
To control the LTC4261 through I2C, install the
QuickEval™ System software on a computer with
an available USB port. The download website is
http://www.linear.com/software. Connect DC590A
between the computer and DC998A, and open the
QuickEval software. If already installed, update the
software to obtain the LTC4261/DC998A driver.
4
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 998A
NEGATIVE HOT SWAP CONTROLLER WITH ADC AND I2C MONITORING
Figure 1. Proper Measurement Equipment Setup
5
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 998A
NEGATIVE HOT SWAP CONTROLLER WITH ADC AND I2C MONITORING
6
Similar pages