19-3092; Rev 0; 12/03
MAX5042 Evaluation Kit
General Description
The MAX5042 evaluation kit (EV kit) is a fully assembled
and tested circuit board that contains a high-efficiency,
high-power, isolated, hot-pluggable, 40W (with ade-
quate cooling) forward DC-DC converter in the industry-
standard half-brick footprint. The circuit is configured for
a +5.0V output voltage and provides up to 8A of current.
Power for the circuit can be provided from either a +36V
to +75V or -36V to -75V DC source used in the tele-
com/datacom markets (48V modules), industrial envi-
ronments, or in automotive 42V power systems.
A high efficiency of up to 85% at 6A and 30W output
power is achieved using a clamped two-transistor
topology. Part of the efficiency improvement is due to
the recovery of stored leakage and magnetizing induc-
tance energy at the primary side. Galvanic isolation is
achieved by an optocoupler and the surface-mount pla-
nar transformer.
Operation at 250kHz allows the use of small magnetics
and output capacitors. The EV kit provides cycle-by-
cycle current-limit protection. Additional steady-state
fault protection is provided by integrating fault protec-
tion and internal thermal shutdown. The MAX5042 also
has a programmable undervoltage lockout (UVLO).
Warning:
The MAX5042 EV kit is designed to operate
with high voltages. Dangerous voltages are present on
this EV kit and on equipment connected to it. Users
who power up this EV kit or power the sources connect-
ed to it must be careful to follow safety procedures
appropriate to working with high-voltage electrical
equipment.
Under severe fault or failure conditions, this EV kit may
dissipate large amounts of power, which could result in
the mechanical ejection of a component or of compo-
nent debris at high velocity. Operate this EV kit with
care to avoid possible personal injury.
Do not short the -VIN pad to the “EV kit Ground” when
the hot-swap MOSFET N1 is off (please consult the
“Absolute Maximum Voltage Rating Diagram” in the
MAX5042 data sheet). The -VIN pad and EV kit ground
are at an 80V difference. The EV kit user should not
probe the circuit with an oscilloscope probe and
ground clip unless they have
high-voltage hot-swap
experience.
Features
♦
Isolated, Hot-Pluggable 40W Forward DC-DC
Converter
♦
±36V to ±75V Input Range
♦
+5V Output Up to 8A (With Adequate Cooling)
♦
V
OUT
Regulation Better than 0.1% Over Line and
Load
♦
85% Efficiency at 48V and 6A
♦
Half-Brick Module Footprint and Pinout
♦
Cycle-by-Cycle Current-Limit Protection
♦
Programmable Integrating Fault Protection
♦
Internal Thermal Shutdown
♦
250kHz Switching Frequency
♦
Designed for 500V Isolation
♦
Soft-Start
♦
Latched Shutdown
♦
Remote Output-Voltage Sense
♦
Fully Assembled and Tested
Evaluates: MAX5042
Ordering Information
PART
MAX5042EVKIT
TEMP RANGE
0°C to +50°C*
IC PACKAGE
56 QFN
*With
100LFM airflow.
Component List
DESIGNATION
C1
QTY
1
DESCRIPTION
220µF ±20%, 100V electrolytic
capacitor (18 x 16.5)
Panasonic EEVFK2A221M
0.033µF ±10%, 250V ceramic
capacitor (1206)
TDK C3216X7R2E333K
1.0µF ±10%, 16V X5R ceramic
capacitors (0805)
Taiyo Yuden EMK212BJ105KG
0.1µF ±10%, 50V X7R ceramic
capacitor (0805)
Taiyo Yuden UMK212BJ104KG
0.0047µF ±10%, 250VAC X7R
ceramic capacitor (2220)
Murata GA355DR7GC472KY
0.1µF ±10%, 16V X7R ceramic
capacitors (0603)
Murata GRM39X7R104K016AD
1.0µF ±10%, 50V X7R ceramic
capacitor (1210)
Taiyo Yuden UMK325BJ105KH
C2
1
C3, C10
2
C4
1
C5
1
C6, C12, C15
3
C7
1
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
MAX5042 Evaluation Kit
Evaluates: MAX5042
Component List (continued)
DESIGNATION
C8
QTY
1
DESCRIPTION
0.33µF ±10%, 10V X5R ceramic
capacitor (0603)
Taiyo Yuden LMK107BJ334KA
220pF ±5%, 50V C0G ceramic
capacitor (0603)
Murata GRM39C0G221J050AD
0.1µF ±10%, 50V X7R ceramic
capacitor (0805)
Murata GRM40X7R104K050AD
1.0µF ±10%, 6.3V X5R ceramic
capacitor (0603)
Taiyo Yuden JMK107BJ105KA
100pF ±2%, 50V C0G ceramic
capacitor (0603) Murata
GRM1885C1H101GA01D
0.001µF, 200V X7R ceramic
capacitor (0603)
Murata GRM39-X7R102K200
150µF, 6.3V aluminum organic
capacitors (X case)
Kemet A700X157M006ATE015
0.15µF ±10%, 16V X7R ceramic
capacitor (0603)
Taiyo Yuden EMK107BJ154KA
0.68µF ±10%, 100V X7R
ceramic capacitors (1812)
TDK C4532X7R2A684K
Not installed, ceramic capacitor
(0603)
0.22µF ±10%, 10V X7R ceramic
capacitor (0603)
TDK C1608X7R1C224K
1000pF ±5%, 50V C0G ceramic
capacitor (0603)
TDK C1608C0G1H102J
100V, 1A Schottky diodes
(SMA)
Diodes Incorporated B1100
40V, 20A Schottky diode
(TO-220AB)
Vishay/General Semiconductor
SBL2040CT
75V, 200mA ultra-fast diode
(SOT-23)
Fairchild MMBD4148
4.4µH, 15A inductor
Pulse Engineering PA1494.442
DESIGNATION
N1
R1
R2
R3
R4, R5
R6
R7, R8, R16, R17
R9
QTY
1
1
1
1
2
1
0
1
DESCRIPTION
100V, 4.6A N-channel MOSFET
(SO-8)
Vishay Siliconix Si4482DY
25.5k,Ω ±1% resistor (0603)
8.25kΩ ±1% resistor (0603)
150Ω ±1% resistor (0805)
10Ω ±5% resistors (0805)
200Ω ±1% resistor (0603)
Not installed, resistors (0603)
15Ω ±5% resistor (0805)
0.025Ω, 0.5W ±1% resistor
(2010)
IRC LRC-2010-R025F or
Dale WSL-2010 0.025 1%
20Ω ±5% resistor (1206)
200kΩ ±1% resistor (0603)
1MΩ ±5% resistor (0603)
27Ω ±5% resistor (0805)
24.9kΩ ±1% resistor (0603)
5.1Ω ±5% resistors (0603)
10kΩ ±5% resistor (1206)
1.24kΩ ±1% resistor (0603)
2kΩ ±5% resistor (0603)
10kΩ ±1% resistor (0603)
51Ω ±5% resistor (0603)
100kΩ ±5% resistor (0805)
0Ω ±5% resistor (0603)
200µH, 50W planar transformer
Pulse Engineering PA0365
MAX5042ATN (56-pin QFN)
30V, 100% to 200% CTR
optically isolated error amplifier
(SO-8)
Fairchild Semiconductor
FOD2712
MAX5042 PC board
Metal screws, 4-40 x 3/8
Nylon screw, 6-32 x 1/4
TO-220 thermally conductive
insulating pad
L-shaped aluminum heatsink
C9
1
C11
1
C13
1
C14
1
R10
1
C16
1
R11
R12
R13
R14
R15
R18, R19
R20
R21
R22
R23
R24
R25
R26
T1
U1
1
1
1
1
1
2
1
1
1
1
1
1
1
1
1
C17, C18
2
C19
1
C20–C23
4
C24
0
C25
1
C26
1
D1, D2
2
U2
1
D3
1
None
None
None
None
None
1
2
1
1
1
D4
L1
1
1
2
_______________________________________________________________________________________
MAX5042 Evaluation Kit
Component Suppliers
SUPPLIER
Diodes Inc.
Fairchild Semiconductor
IRC
Kemet
Murata
Panasonic
Pulse Engineering
Taiyo Yuden
TDK
Vishay/Dale
Vishay/General Semiconductor
Vishay/Siliconix
PHONE
805-446-4800
888-522-5372
361-992-7900
864-963-6300
770-436-1300
714-373-7366
858-674-8100
800-348-2496
847-803-6100
402-564-3131
760-804-9258
610-644-1300
FAX
805-446-4850
—
361-992-3377
864-963-6322
770-436-3030
714-737-7323
858-674-8262
847-925-0899
847-390-4405
402-563-6296
760-804-9259
—
WEBSITE
www.diodes.com
www.fairchildsemi.com
www.irctt.com
www.kemet.com
www.murata.com
www.panasonic.com
www.pulseeng.com
www.t-yuden.com
www.component.tdk.com
www.vishay.com
www.vishay.com
www.vishay.com
Evaluates: MAX5042
Note:
Please indicate that you are using the MAX5042 when contacting these component suppliers.
Quick Start
Required Equipment
• ±36V to ±75V power supply capable of providing 3A
• Voltmeter
• A fan to provide at least 100LFM airflow for extend-
ed operation at 8A.
The MAX5042 EV kit is fully assembled and tested.
Follow these steps to verify board operation.
Do not
turn on the power supply until all connections are
completed.
Detailed Description
The MAX5042 EV kit is an isolated, hot-pluggable, 40W
forward DC-DC converter that provides +5V at up to 8A
output with adequate cooling. The circuit can be powered
from a +36V to +75V or a -36V to -75V DC source.
Caution: Refer to the “Absolute Maximum Voltage
Rating Diagram” in the MAX5042 data sheet when
attempting to connect test equipment to the EV kit.
The MAX5042 IC controls the hot-pluggable circuit, limit-
ing the inrush current and rise time of the voltage to the
40W forward DC-DC converter circuit. The hot-pluggable
circuit feature is provided by MOSFET N1, UVLO resistors
R16/R17, the
HSOK
pad, and one MAX5042. When the
MAX5042 EV kit is inserted into a live backplane system,
the MAX5042 controls the turn-on rate of MOSFET N1
once the UVLO is above +30V (default UVLO). After
MOSFET N1 is completely enhanced, the
HSOK
pad
open-drain signal pulls low indicating that the hot swap
was successful. Next, the 40W forward DC-DC converter
circuit starts switching at 250kHz. Note that the IC paddle
is connected to the -VIN power rail and when MOSFET N1
is fully enhanced, the primary-side ground is connected
to the -VIN power rail. Jumper JU2 is provided to bypass
hot-plugging MOSFET N1. When using JU2, note that it
will carry the full primary current.
Forward DC-DC Converter Output
1) Connect a jumper wire from the VOUT pad to the
+SENSE pad.
2) Connect a jumper wire from the SGND pad to the
-SENSE pad.
3) Connect a voltmeter to the VOUT and SGND pads.
4) Connect the 36V to 75V power supply to the +VIN
pad. Connect the power supply’s ground to the -VIN
pad.
Do not exceed 80V input voltage.
5) Turn on the power supply above 36V and verify that
VOUT provides +5V at the voltmeter.
For instructions on selecting the feedback resistors for
other output voltages, see the
Evaluating Other Output
Voltages
section.
_______________________________________________________________________________________
3
MAX5042 Evaluation Kit
The 40W forward converter achieves high efficiency by
using a clamped two-transistor power topology with both
power transistors integrated on the MAX5042 IC. Cycle-
by-cycle current limiting protects the converter against
short circuits at the output. Current-sense resistor R10
senses the current through the primary of transformer T1
and then turns off both internal transistors when the
156mV trip level is reached. For a continuous short cir-
cuit at the output, the MAX5042’s fault integration feature
provides hiccup fault protection, thus greatly minimizing
destructive temperature rise.
The planar surface-mount transformer features a bias
winding, which, along with diode D4, resistor R9, and
capacitor C7, powers the MAX5042 IC after PWM start-
up is complete. A reset winding is not required with a
clamped two-transistor power topology. Schottky
diodes D1 and D2 recover the magnetic energy stored
in the core and feed it back to the +VIN input when
both internal transistors turn off. The transformer pro-
vides galvanic isolation.
On the transformer’s secondary side, optically isolated
error amplifier U2 along with feedback resistors R1 and
R2 provide voltage feedback to the primary side. The
MAX5042 receives the voltage feedback signal on the
primary side. Biasing resistor R21 provides biasing for
the optocoupler transistor while the resistor/capacitor
network R6/C8 provides compensation.
Remote output-voltage sensing is provided by the
+SENSE and -SENSE for accurate output-voltage regu-
lation across the load. The soft-start feature allows the
output voltage to slowly ramp up in a controlled manner
within 4ms. The MAX5042 switches at a preconfigured
250kHz frequency set by resistor R15 and capacitor
C14. The output provides up to 8A of continuous cur-
rent when a cooling fan with at least 100LFM airflow is
used. Dual-diode D3’s heatsink is connected to SGND.
The 6-layer PC board layout and component placement
has been designed for the industry-standard half-brick
footprint and pinout. Resistor/capacitor network R14 and
C2 prevent voltage overshoot as a result of the ±VIN
input line inductance when hot plugging the EV kit.
Evaluates: MAX5042
Shutdown
Shutdown Mode
The MAX5042 EV kit features a jumper pad (JU1) and a
hole-pad (SHDN) to remotely shut down the hot-plug-
gable, 40W forward DC-DC converter. Once the
MAX5042 EV kit is shut down by either jumper method,
the power to the EV kit must be cycled on/off before the
MAX5042 starts switching again. Jumper pad JU1 can be
used to manually shut down. An isolated optocoupler with
an open-collector/drain transistor or relay contact can be
connected across jumper JU1 to remotely shut down the
EV kit.
Evaluating Other Output Voltages, Current
Limits, Soft-Starts and UVLOs
VOUT Output Voltage
The MAX5042 EV kit’s output (VOUT) is set to +5.0V by
feedback resistors R1 and R2. To generate output volt-
ages other than +5.0V (from +3.2V to +5.0V), select dif-
ferent voltage-divider resistors (R1, R2). Resistor R1 is
typically chosen to be less than 25kΩ. Using the
desired output voltage, resistor R2 is then found by the
following equation:
R2
=
R1
V
OUT
−
1
V
REF
where V
REF
is 1.24V and V
OUT
is the desired output
voltage.
The maximum output current should be limited to less
than 8A. The usable output voltage range for the EV kit
is +3.2V to +5.0V. U2 and resistor R3 limit the minimum
output voltage (V
OUT
) to +3.2V.
4
_______________________________________________________________________________________
MAX5042 Evaluation Kit
Current Limiting
The EV kit features cycle-by-cycle current limiting for
the transformer primary current. The MAX5042 IC turns
off both internal switching transistors when the voltage
across the CSP and CSN pins of the MAX5042 reaches
156mV. Current-sense resistor R10 (R10 = 0.025Ω) lim-
its the peak primary current to approximately 6.2A
(156mV/0.025Ω = 6.2A). This limits short-circuit current
on the secondary output (VOUT) to approximately 14A.
To evaluate lower current limits, current-sense resistor
R10 must be replaced with a different value surface-
mount resistor (1206 size) as determined by the follow-
ing equation:
R10
=
V
SENSE
N
S
×
1.9
×
I
OUT(MAX)
N
P
Undervoltage Lockout (UVLO)
The MAX5042 EV kit features a UVLO circuit that pre-
vents operation below the programmed input supply
start voltage. Resistors R7 and R8 set the EV kit’s input
voltage brownout UVLO. To evaluate input UVLO volt-
ages other than the default (31.5V), install resistors R7
and R8 (0603 size) with the desired resistor values.
Using the startup voltage, resistor R7 is then found by
the following equation:
V
IN(STARTUP)
−
1.24V
R7
=
1.24V
Evaluates: MAX5042
(
)
×
R8
where V
IN
(
STARTUP)
is the desired startup voltage at
which the EV kit starts and resistor R8 is typically 10kΩ.
Calculating the Hot-Swap MOSFET Snubber
Resistor/Capacitor Values
Resistor R14 and capacitor C2 are series connected
across the drain/source terminals of hot-swap MOSFET
N1 to prevent voltage overshoot as a result of the ±VIN
input line inductance when hot-plugging the EV kit. To
calculate new values for capacitor C2 and resistor R14
use the following equations:
C2
=
75
×
C
DS _ 30V
R7
=
1
×
3
L
WIRING
C
DS _ 30V
where V
SENSE
= 0.156V, N
S
= 4, N
P
= 10 and
I
OUT(MAX)
= maximum DC output current (8A as config-
ured). There are errors introduced as a result of the
presence of the transformer’s magnetic inductance and
output inductor ripple current.
Soft-Start
The MAX5042 EV kit limits the output voltage rate of
rise with a soft-start feature. Capacitor C11 (0.1µF),
sets the ramp time to approximately 4ms. To evaluate
other soft-start ramp times, replace capacitor C11 with
another surface-mount capacitor (0805 size) as deter-
mined by the following equation:
32
µ
A
×
soft start _ time
C11
=
1.4 V
where soft start_time is the desired soft-start time in
seconds.
where: C
DS_30V
is the hot-swap MOSFET N1 drain-to-
source approximate capacitance at a 30V bias point.
L
WIRING
is the total approximate inductance of the wiring
or backplane connected to the EV kit’s ±V
IN
inputs.
_______________________________________________________________________________________
5
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