General Description
The MAX17498B evaluation kit (EV kit) is a fully
assembled and tested circuit board that contains an
isolated 7W flyback DC-DC converter. The circuit uses
the MAX17498B current-mode, fixed-frequency flyback
converter in a 16-pin TQFN package with an exposed
pad. The EV kit demonstrates the IC’s cycle-by-cycle
current limit, soft-start, and UVLO features.
The EV kit circuit output is configured for an isolated
+5V and provides up to 1.5A of current. Low cost and
high efficiency up to 88% are achieved using a flyback
DC-DC converter topology operating at a fixed 500kHz
switching frequency. The surface-mount transformer
provides up to +1500V galvanic isolation at the output.
The EV kit operates from a +18V to +36V power supply
capable of providing up to 1A.
Features
S +18V to +36V DC Voltage Input Range
S Isolated 5V, 1.5A Output
S Fixed 500kHz Switching Frequency
S 88% Efficiency
S Cycle-by-Cycle Current Limit
S High-Accuracy UVLO
S PGOOD Open-Drain Output
S Low-Cost Flyback Design
S Configurable for Primary-Side Regulation
S Proven PCB Layout
S Fully Assembled and Tested
DESIGNATION QTY DESCRIPTION
C1 1
47µF Q20%, 63V electrolytic
capacitor (8mm x 10.2mm)
Panasonic EEE-FK1J470P
C2, C4 2
4.7µF Q10%, 50V X7R ceramic
capacitors (1210)
Murata GRM32ER71H475KA88L
C3 1
33nF Q10%, 50V X7R ceramic
capacitor (0805)
Murata GRM219R71H333K
C5 1
0.22µF Q10%, 50V X7R ceramic
capacitor (0603)
Murata GCM188R71H224KA64D
C6 1
2.2µF Q10%, 16V X7R ceramic
capacitor (0805)
Murata GRM21BR71C225KA12L
C7 1
47pF Q5%, 50V C0G ceramic
capacitor (0603)
Murata GRM1885C1H470J
C8, C18 0
Not installed, capacitors (0603)
C8 is short (PC trace) and
C18 is open
C9 1
68nF Q10%, 16V X7R ceramic
capacitor (0603)
Murata GRM188R71C683K
DESIGNATION QTY DESCRIPTION
C10 1
100pF Q5%, 50V C0G ceramic
capacitor (0603)
Murata GRM1885C1H101JA01D
C11 1
2.2µF Q10%, 10V X7R ceramic
capacitor (0805)
Murata GRM21BR71A225KA01L
C12, C13, C14 3
22µF Q10%, 16V X7R ceramic
capacitors (1210)
TDK C3225X7R1C226K
C15 1
4.7nF Q10%, 50V X7R ceramic
capacitor (0603)
Murata GRM188R71H472KA01D
C16 1
33pF Q5%, 50V X7R ceramic
capacitor (0603)
Murata GRM1885C1H330JA01D
C17 0 Not installed, capacitor (0805)
D1 1 150V, 1A rectifier (SMA)
Diodes Inc. ES1C-13-F
D2 1 40V, 300mA rectifier (SOD123)
Diodes Inc. SD103AW-13-F
D3 1 50V, 5A rectifier (SMC)
Diodes Inc. B550C-13-F
D4 0 Not installed, diode (SOT323)
MAX17498B Evaluation Kit
Evaluates: MAX17498B
_________________________________________________________________ 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.
19-6293; Rev 0; 4/12
Ordering Information appears at end of data sheet.
Component List
DESIGNATION QTY DESCRIPTION
R1 1
7.5kI Q1%, 1/2W resistor (1206)
Stackpole Electronics
RNCP1206FTD7K50
R3 1 348kI Q1% resistor (0603)
R4 1 20kI Q1% resistor (0603)
R5, R9, R19 310kI Q1% resistors (0603)
R6 1 86.6kI Q1% resistor (0603)
R7 1 0I Q5% resistor (0603)
R8, R10, R14,
R16, R17,
R21, R22
0Not installed, resistors (0603)
R11, R18 215kI Q1% resistors (0603)
R12 1 10kI Q5% resistor (0603)
R13 1 511I Q1% resistor (0603)
DESIGNATION QTY DESCRIPTION
R15 1 1kI Q1% resistor (0603)
R20 1 30.1kI Q1% resistor (0603)
T1 1 30W transformer (1:2:4)
Coilcraft MA5237-AL
U1 1
Offline 500kHz peak current-mode
controller (16 TQFN-EP*)
Maxim MAX17498BATE+
U2 1
Phototransistor/optocoupler
(6 Dip Gull Wing)
Avago 4N35-300E
U3 1 1.24V shunt regulator (3 SOT23)
Diodes Inc. TLV431BFTA
— 1 PCB: MAX17498B EVALUATION
KIT
SUPPLIER PHONE WEBSITE
Coilcraft, Inc. 847-639-6400 www.coilcraft.com
Diodes Incorporated 805-446-4800 www.diodes.com
Murata Electronics North America, Inc. 770-436-1300 www.murata-northamerica.com
Panasonic Corp. 800-344-2112 www.panasonic.com
TDK Corp 847-803-6100 www.component.tdk.com
_________________________________________________________________ Maxim Integrated Products 2
MAX17498B Evaluation Kit
Evaluates: MAX17498B
*EP = Exposed pad.
Component List (continued)
Component Suppliers
Note: Indicate that you are using the MAX17498B when contacting these component suppliers.
Quick Start
Required Equipment
• MAX17498B EV kit
• +18V to +36V power supply capable of providing up
to 1A
• Two voltmeters
• Electronic load capable of sinking 1.5A
Procedure
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 VIN and PGND PCB
pads.
2) Connect the second voltmeter to the VOUT and GND
PCB pads.
3) Connect the positive and negative terminals of the
electronic load to the VOUT and PGND banana jacks,
respectively.
4) Connect the power supply’s positive terminal to the
VIN PCB pad. Connect the power supply’s ground to
the PGND PCB pad.
5) Turn on the power supply above +18V.
6) Enable the electronic load and set it to 1.5A.
7) Verify that the voltmeter at VOUT reads approximately
+5V.
Detailed Description of Hardware
The MAX17498B EV kit is a fully assembled and tested
circuit board that contains the MAX17498B isolated 7W
flyback DC-DC converter. The EV kit circuit output pro-
vides +5V and can supply up to 1.5A. The circuit can be
powered from a +18V to +36V DC source.
The flyback DC-DC converter operates at a fixed 500kHz
operating frequency and achieves up to 88% efficiency.
The EV kit provides cycle-by-cycle, primary-side current-
limit protection using the IC’s internal MOSFET switch,
which is connected at the LX input. Resistor R6 sets
_________________________________________________________________ Maxim Integrated Products 3
MAX17498B Evaluation Kit
Evaluates: MAX17498B
the circuit peak current limit to 1.7A using transformer
T1’s primary winding and the IC internal switch. The EV
kit features an RCD snubber network (R1, C3, and D1)
to minimize leakage energy ringing and to clamp the
voltage at the LX input. The surface-mount transformer
provides galvanic isolation up to +1500V for the output.
The isolated +5V output is set using the transformer
secondary-side, opto-coupler (U2), shunt regulator (U3),
resistors (R9, R19, R20), and various other components.
The EV kit circuit startup process begins when the volt-
age at IN is greater than the circuit’s +15.6V undervolt-
age threshold and a current-limit fault is not present.
Resistors R3, R4, and R5 set the undervoltage- and
overvoltage-threshold voltages to +15.6V and +46V,
respectively. Soft-start capacitor C9 programs the circuit
soft-start period to 8ms. Upon the circuit rising above
its undervoltage lockout (UVLO), the LX node begins
switching and energy is transferred from the transformer
primary side to the secondary side for the regulated +5V
output.
UVLO provides controlled turn-on and shutdown during
brownouts, power-up, or power-down. The EV kit circuit
UVLO is set to +15.6V. The circuit overvoltage threshold
(OVI) is set to +46V. EN/UVLO and OVI PCB pads are
available for monitoring the voltages at the IC’s EN/UVLO
and OVI inputs, respectively.
The EV kit circuit can also be reconfigured for primary-
side regulation using the transformer bias winding and
feedback resistors R8 and R10. See the Reconfiguring the
EV Kit for Primary-Side Regulation section for additional
information. Also refer to the MAX17498A/MAX17498B/
MAX17498C IC data sheet for additional information.
Current Limiting
The IC features current limiting for the transformer’s
primary side by monitoring the peak current entering the
IC’s LX input. Resistor R6 sets the EV kit circuit current
limit to 1.7A. The IC turns off its internal switch when the
peak current reaches the current limit. To reconfigure the
peak current limit to a different value, use the following
equation to choose a new R6 resistor:
R6 = 50 x IPEAK
where IPEAK is in amps and R6 is in kI.
Undervoltage Lockout and
Overvoltage Protection
The EV kit features UVLO and OVI circuits that prevent
operation below the programmed input supply startup
voltage and above the overvoltage threshold. Resistors
R3, R4, and R5 set the undervoltage and overvoltage
thresholds. The circuit’s undervoltage and overvoltage
thresholds are set at +15.6V and +46V, respectively.
To reconfigure the UVLO and OVI voltages, refer to the
Startup Voltage and Input Overvoltage-Protection Setting
(EN/UVLO, OVI) section in the MAX17498A/MAX17498B/
MAX17498C IC data sheet
EN/UVLO and OVI PCB pads are available for monitoring
the voltages present at the respective inputs.
Power-Good Output (PGOOD)
The EV kit provides a PCB pad to monitor the status of the
power-good output. PGOOD is high when VOUT is within
5% of its regulated voltage. When VOUT falls below 92%
(typ) of its regulated voltage, PGOOD is pulled low.
PGOOD is pulled up to VCC through resistor R12.
Reconfiguring the EV Kit for
Primary-Side Regulation
The EV kit also supports an isolated DC-DC converter
design using primary-side regulation. The transformer’s
bias winding and resistor PCB pads R8 and R10 are
used to set the EV kit circuit output voltage. When recon-
figuring the EV kit for primary-side regulation, the follow-
ing modifications must be made:
• Remove resistors R13, R15, and R20
• Replace resistor R9 with a 0I 0603 footprint
• Install required 0603 resistors R8 and R10 for feed-
back regulation
• Install required 0603 capacitors C7 and C8 for loop
compensation
Refer to the MAX17498A/MAX17498B/MAX17498C IC
data sheet for selecting R8, R10, C7, and C8.
_________________________________________________________________ Maxim Integrated Products 4
MAX17498B Evaluation Kit
Evaluates: MAX17498B
Figure1. MAX17498B EV Kit Schematic
1.0’’
1.0’’
1.0’’
_________________________________________________________________ Maxim Integrated Products 5
MAX17498B Evaluation Kit
Evaluates: MAX17498B
Figure 2. MAX17498B EV Kit Component Placement Guide—
Component Side
Figure 4. MAX17498B EV Kit PCB Layout—Solder Side
Figure 3. MAX17498B EV Kit PCB Layout—Component Side
PART TYPE
MAX17498BEVKIT# EV Kit
_________________________________________________________________ Maxim Integrated Products 6
MAX17498B Evaluation Kit
Evaluates: MAX17498B
Ordering Information
#Denotes RoHS compliant.
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 4/12 Initial release —
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 7
© 2012 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX17498B Evaluation Kit
Evaluates: MAX17498B
Revision History
