19-5764; Rev 0; 2/11
MAX17500A Evaluation Kit
Evaluates: MAX17500A
General Description
The MAX17500A evaluation kit (EV kit) is a fully assem-
bled and tested circuit board that contains a 9W flyback
DC-DC converter. The circuit is configured for +5V and
+15V output voltages and provides up to 1.5A and
100mA of current at each respective output. Power for
the circuit can be provided from either a +36V to +72V
or -36V to -72V DC source.
High efficiency up to 81% is achieved using a flyback
DC-DC converter topology. The surface-mount transformer
provides up to +1500V galvanic isolation for both outputs.
Low cost is achieved through the use of primary-side
regulation, while undervoltage lockout (UVLO) and digital
soft-start provide for a robust 9W isolated power supply.
Operation at 350kHz allows the use of small magnetics
and output capacitors.
Warning:
The 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 connected 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 component
debris at high velocity. Operate this kit with care to avoid
possible personal injury.
S
Isolated Outputs
Features
S
+36V to +72V or -36V to -72V DC Input Range
V
OUT1
: +5V Provides Up to 1.5A
V
OUT2
: +15V Provides Up to 100mA
S
±5% (typ) Load Regulation for the +5V Output Set
Point (150mA to 1.5A)
S
81% Efficiency at +48V Input and Full Load
S
Cycle-by-Cycle Current Limit
S
350kHz Switching Frequency
S
Digital Soft-Start
S
High-Accuracy UVLO
S
UVLO Open-Drain Flag Output
S
Designed for +1500V Isolation with Primary-Side
Regulation
S
Low-Cost Flyback Design
S
Proven PCB Layout
S
Fully Assembled and Tested
Ordering Information
appears at end of data sheet.
Component List
DESIGNATION
C1, C2
QTY
2
DESCRIPTION
1FF
Q10%,
100V X7R ceramic
capacitors (1812)
TDK C4532X7R2A105K
68FF, 6.3V electrolytic capacitor (V)
KEMET A700V686M006ATE028
22FF
Q20%,
6.3V X5R ceramic
capacitor (1206)
TDK C3216X5R0J226M
47FF, 25V electrolytic capacitor
(6.3mm x 5.8mm)
Panasonic EEVFK1E470P
0.0047FF
Q10%,
250V AC X7R
ceramic capacitor (1825)
Murata GA355DR7GC472KY02L
DESIGNATION
C7, C11
QTY
2
DESCRIPTION
0.22FF
Q10%,
50V X7R ceramic
capacitors (0805)
Murata GRM21BR71H224KA01B
Not installed, ceramic capacitors
(0603)
100pF
Q2%,
50V C0G ceramic
capacitor (0603)
Murata GRM1885C1H101G
15FF
Q10%,
35V tantalum
capacitor (D)
KEMET T491D156K035AS
1FF
Q10%,
16V X7R ceramic
capacitor (0805)
TDK C2012X7R1C105KT
C3
1
C8, C10, C19
0
C4
1
C9
1
C5
1
C12
1
C6
1
C13
1
_________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX17500A Evaluation Kit
Evaluates: MAX17500A
Component List (continued)
DESIGNATION
C14
QTY
1
DESCRIPTION
3900pF
Q10%,
50V X7R ceramic
capacitor (0603)
Murata GRM188R71H392K
1FF
Q10%,
25V X7R ceramic
capacitor (0805)
TDK C2012X7R1E105KT
1FF
Q10%,
50V X7R ceramic
capacitor (1206)
Murata GRM31MR71H105K
Not installed, ceramic capacitor
(0805)
0.1FF
Q10%,
25V X7R ceramic
capacitor (0603)
Murata GRM188R71E104K
40V, 10A Schottky diode
(PowerDI
M
5)
Diodes Inc. PDS1040-13
200V, 1.5A super-fast diode (SMD)
Vishay BYG20D
Not installed, 250V, 250mA high-
voltage switching diode (SOD123)
Central Semi CMHD2003
recommended
5.6V, 0.5W zener diode (SOD123)
Diodes Inc. BZT52C5V6
18V, 0.5W zener diode (SOD123)
Diodes Inc. BZT52C18
75V, 250mA high-speed diode
(SOT23)
Central Semi CMPD914
Not installed, 14V, 250mW zener
diode (SOD323)
Central Semi CMDZ5244B
recommended
DESIGNATION
D8
JU1
L1
L2
QTY
1
1
1
1
DESCRIPTION
40V, 0.5A Schottky diode (SOT23)
Zetex ZHCS500
2-pin header
3A ferrite-bead inductor (1806)
Fair-Rite 2518066007Y3
100mA ferrite-bead inductor (0805)
Fair-Rite 2508051027Y0
200V, 1.2A n-channel MOSFET
(8 SO)
IR IRF7464PBF
22.6kI
Q1%
resistor (0603)
2.49kI
Q1%
resistor (0603)
1.37MI
Q1%
resistor (0805)
51.1kI
Q1%
resistor (0805)
0.600I
Q1%
power resistor (1206)
IRC LRC-LR1206LF-01-R600-F
33kI
Q5%
resistor (1206)
1.2kI
Q5%
resistors (1206)
Not installed, resistor (1206)
75kI
Q1%
resistor (0603)
4.7I
Q5%
resistor (0805)
100I
Q5%
resistor (0603)
10kI
Q5%
resistor (0805)
14.3kI
Q1%
resistor (0805)
750I
Q5%
resistor (0603)
35FH, 10W, 1:0.536:0.214:0.429 turn
350kHz transformer (10 gull wing)
Cooper Bussmann CTX03-17492-R
Current-mode PWM controller
(10
FMAX
M
)
Maxim MAX17500AEUB+
Rubber bumpers
Shunt (JU1)
PCB: MAX17500A EVALUATION KIT
C15
1
C16
1
N1
R1
R2
R3
R4
R5
R6
R7, R12
R8
R9
R10
R11
R13
R14
R15
T1
1
1
1
1
1
1
1
2
0
1
1
1
1
1
1
1
C17
0
C18
1
D1
1
D2
1
D3
0
D4
D5
1
1
D6
1
U1
—
—
—
1
4
1
1
D7
0
PowerDI is a registered trademark of Diodes Incorporated.
µMAX is a registered trademark of Maxim Integrated Products,
Inc.
_________________________________________________________________
Maxim Integrated Products
2
MAX17500A Evaluation Kit
Evaluates: MAX17500A
Componets Suppliers
SUPPLIER
Central Semiconductor Corp.
Cooper Bussmann
Diodes Incorporated
Fair-Rite Products Corp.
International Rectifier
IRC, Inc.
KEMET Corp.
Murata Electronics North America, Inc.
Panasonic Corp.
TDK Corp.
Vishay
Zetex Semiconductor (now a Division of Diodes Incorporated)
PHONE
631-435-1110
916-941-1117
805-446-4800
845-895-2055
310-322-3331
361-992-7900
864-963-6300
770-436-1300
800-344-2112
847-803-6100
402-563-6866
805-446-4800
WEBSITE
www.centralsemi.com
www.cooperet.com
www.diodes.com
www.fair-rite.com
www.irf.com
www.irctt.com
www.kemet.com
www.murata-northamerica.com
www.panasonic.com
www.component.tdk.com
www.vishay.com
www.diodes.com
Note:
Indicate that you are using the MAX17500A when contacting these component suppliers.
Quick Start
•
MAX17500A EV kit
Required Equipment
For instructions on selecting the feedback resistors for
other output voltages, see the
Evaluating Other Output
Voltages, Current Limits, and Undervoltage Lockouts
section.
•
+36V to +72V power supply capable of providing up
to 1A
•
Two voltmeters
•
22µF, +100V bulk-storage capacitor to be connected
to the input terminals on the EV kit
The EV kit is fully assembled and tested. Follow the steps
below to verify board operation.
Caution: Do not turn on
the power supply until all connections are completed.
1) Connect the first voltmeter to the VOUT1 and SGND
PCB pads.
2) Connect the second voltmeter to the VOUT2 and
SGND PCB pads.
3) Connect a 750mA load to VOUT1 and a 50mA load to
VOUT2.
4) Verify that a shunt is not installed on jumper JU1
(SHDN).
5) Connect the power supply’s positive terminal to the
+VIN PCB pad. Connect the power supply’s ground
to the -VIN PCB pad.
6) Turn on the power supply above +36V and verify that
the voltmeter at VOUT1 reads approximately +5V.
7) Verify that the voltmeter at VOUT2 reads approxi-
mately +15V.
The maximum current for each output should be limited
to less than 1.5A for VOUT1 and 100mA for VOUT2.
Detailed Description of Hardware
The MAX17500A EV kit is a fully assembled and tested
circuit board that contains a 9W isolated flyback DC-DC
converter that provides a +5V and +15V output. The
+5V output (V
OUT1
) provides up to 1.5A and the +15V
output (V
OUT2
) provides up to 100mA. The circuit can be
powered from either a +36V to +72V or -36V to -72V DC
source.
The user must supply at least 22µF of bulk-
storage capacitance at the input terminals (+VIN, -VIN).
The capacitor should be rated for +100V and be able to
carry approximately 200mA of ripple current.
The flyback DC-DC converter achieves up to 81%
efficiency. The single-transistor topology and primary-side
regulation provide for a low-cost design by eliminating
the need for an optocoupler and shunt reference on the
secondary side. The EV kit provides cycle-by-cycle,
primary-side current-limit protection. Current-sense
resistor R5 senses the current through the transformer’s
(T1) primary winding, switching transistor (N1), and turns
off the transistor when the trip level of +1V is reached. The
surface-mount transformer provides galvanic isolation up
to +1500V for both outputs. The EV kit features PCB pads
for an RCD snubber network (R8, C10, D3) to minimize
leakage energy ringing and clamp the voltage at the drain
of MOSFET N1 during switching (with most MOSFETs this
snubber circuit can be eliminated).
Primary-side regulation through feedback resistors
R1 and R2, rectifier D6, and transformer T1 tertiary
Procedure
_________________________________________________________________
Maxim Integrated Products
3
MAX17500A Evaluation Kit
Evaluates: MAX17500A
windings provide
Q5%
regulation for the +5V output set
point. Resistors R7 and R12 are adjusted to preload
the tertiary winding for the desired +5V output set point
and regulation. UVLO provides controlled turn-on and
shutdown during brownouts, power-up, or power-down.
The UVLO settings can be changed by replacing
resistor R3. Startup resistor R6 and reservoir capacitor
C16 enable the device to start up within approximately
37ms. The digital soft-start allows the output voltage to
slowly ramp up in a controlled manner within 6ms.
The device controller switches at a fixed 350kHz
frequency and is set by resistor-capacitor networks R14,
R15/C18, and C19. The switching duty cycle is varied
to control energy transfer to the isolated outputs. The
maximum duty cycle is 50% for the EV kit’s discontinuous
current-mode flyback design.
where:
V
OUT1
is the +5V output.
N
T
= 15 is the transformer’s tertiary turns.
N
1
= 6 is the transformer’s secondary V
OUT1
, +5V
output turns.
V
FB
= +1.23V is the device reference voltage.
V
VD6
= +1V is the circuit’s tertiary winding, high-speed
diode D6 forward-voltage drop.
V
VD1
= +0.45V (typ) is the circuit’s secondary-side
Schottky diode D1 forward-voltage drop at 1.5A.
Both output voltages are scaled up or down since the
respective transformer’s secondary output turns set the
actual voltage. Additionally, the maximum current for
each output should be limited to less than 1.5A for V
OUT1
and 100mA for V
OUT2
.
Current Limiting
The EV kit features current limiting for the transformer’s
primary current. The device turns off switching MOSFET
N1 when the voltage at the device’s CS pin reaches +1V.
Current-sense resistor R5 (0.6I) limits the transformer
peak primary current to 1.67A (+1V/0.6I = 1.67A). This
limits the average short-circuit current on the secondary
outputs typically to 1.42A (average with I
OUT2
= 100mA)
and 0.52A (average with I
OUT1
= 1.5A) for V
OUT1
and
V
OUT2
, respectively. To evaluate a lower current limit,
current-sense resistor R5 must be replaced with a different
surface-mount resistor (1206 size), as determined by the
following equation.
When considering the transformer’s primary input
current:
R5 = (V
SENSE
/I
PRIMARY
)
where V
SENSE
= +1V and I
PRIMARY
is the transformer’s
maximum primary current.
Undervoltage Lockout (UVLO)
The EV kit features an accurate UVLO circuit that
prevents operation below the programmed input-supply
start voltage. Resistors R3 and R4 set the voltage at
the device’s UVLO/EN pin, which determines the UVLO
wake-up and shutdown levels of +1.23V (typ) and +1.17V
(typ), respectively. To evaluate other wake-up and shut-
down levels, replace R3 with another surface-mount
The EV kit features two methods to shut down the
flyback DC-DC converter. Jumper JU1 can be used to
shut down the flyback DC-DC converter. An alternate
method, remote-control shutdown, can be done with a
user-supplied open-collector/drain transistor or relay
contact connected to the
SHDN
and -VIN PCB pads on
the EV kit. Table 1 lists the shutdown mode.
Shutdown Mode (Jumper and
Remote-Control Methods)
Evaluating Other Voltages,
Current Limits, and Undervoltage Lockouts
V
OUT1
and V
OUT2
Output Voltages
The EV kit’s outputs (V
OUT1
and V
OUT2
) are set
to +5V and +15V, respectively, by the T1 transformer
tertiary windings, the transformer’s respective secondary
output windings, and the resistor-divider R1 and R2. To
generate scaled output voltages other than +5V (+4.2V
to +6.8V) and +15V (+12.3V to +20.2V), select different
voltage-divider resistors (R1, R2). Resistor R2 is typically
chosen to be less than 5kI.
When evaluating other
output voltages, verify that the secondary outputs’
components affected by increased voltage are rated
for the appropriate voltage. Components C3, C4, C13,
and D4 of V
OUT1
and components C5, C15, and D5
should have their respective voltage rating evaluated.
Using the desired scaled output voltages, resistor R1 is
then found by the following equation:
R1 = [[{(V
OUT1
- V
VD1
) x N
T
/N
1
} - V
VD6
]/V
FB
-1] x R2
Table 1. Jumper JU1 Shutdown Mode
SHUNT POSITION
Not installed
Installed
DEVICE UVLO/EN PIN
UVLO resistors R3 and R4 determine startup voltage
Pulled low to -VIN
DEVICE OUTPUT
Device enabled
Shutdown mode
_________________________________________________________________
Maxim Integrated Products
4
MAX17500A Evaluation Kit
Evaluates: MAX17500A
resistor (0805 size). Refer to the
Undervoltage Lockout
section in the MAX17499/MAX17500 IC data sheet for
instructions on selecting resistor R3, as determined by
the following equation:
R3 = ((V
IN
- V
UVLO
)/V
UVLO
) x R4
where V
IN
is the +36V to +72V supply voltage applied
between the +VIN and -VIN PCB pads on the EV kit and
V
UVLO
= +1.23V (typ).
UVLO Flag (UFLG and FLG_PULL)
The EV kit features an open-drain UVLO flag output at
the UFLG PCB pad. The UFLG signal can be used to
indicate that a UVLO condition has occurred. A voltage
source of up to +25V can be connected to the PCB’s
FLG_PULL PCB pad, which, along with resistor R13,
pulls up the UFLG signal. Refer to the
UVLO Flag (UFLG)
section in the MAX17499/MAX17500 IC data sheet for
instructions and additional information on using the
device’s UFLG pin.
Flyback Converter Waveforms
EFFICIENCY vs. OUTPUT CURRENT
90
80
70
EFFICIENCY (%)
60
50
40
30
20
10
0
0
0.3
0.6
0.9
1.2
1.5
2ms
I
OUT1
(A)
OUTPUT TURN-0N VOLTAGE TRANSIENT
V
OUT1
2V/div
V
OUT2
= +15V, 100mA
V
OUT2
= +15V, 25mA
V
OUT2
5V/div
Figure 1. Efficiency vs. Output Current I
OUT1
(+VIN = +48V)
Figure 2. Output-Voltage Transient at Power-Up (+VIN = +48V,
Channel 1 = V
OUT1
(I
OUT1
= 150mA), and Channel 2 = V
OUT2
(I
OUT2
= 25mA))
V
OUT1
REGULATION vs. I
OUT1
6.0
5.8
5.6
5.4
V
OUT1
(V)
V
OUT2
(V)
5.2
5.0
4.8
4.6
4.4
4.2
4.0
0
0.3
0.6
0.9
1.2
1.5
I
OUT1
(A)
V
OUT2
= +15V, 100mA
V
OUT2
= +15V, 25mA
18.0
17.6
17.2
16.8
16.4
16.0
15.6
15.2
14.8
14.4
14.0
0
V
OUT2
REGULATION vs. I
OUT2
V
OUT1
= +5V, 150mA
V
OUT1
= +5V, 1.5A
0.02
0.04
0.06
0.08
0.10
I
OUT2
(A)
Figure 3. V
OUT1
(+5V) Output-Voltage Regulation
Figure 4. V
OUT2
(+15V) Output-Voltage Regulation
_________________________________________________________________
Maxim Integrated Products
5
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