General Description
The MAX16955 evaluation kit (EV kit) is a fully assem-
bled and tested PCB that contains all the components
necessary to evaluate the performance of the MAX16955
synchronous PWM step-down controller. The device is
available in a 16-pin TSSOP package and features an
exposed pad for enhanced thermal dissipation.
The EV kit requires a 6V to 36V power supply for normal
operation. The EV kit output is configured to 5V and can
deliver up to 5A output current. The EV kit can be easily
reconfigured to operate the controller in continuous PWM
mode, SKIP mode, or external synchronization operation.
The controller switching frequency is set to 400kHz. The
EV kit includes a jumper to enable the cir cuit and an LED
to monitor the power-good output.
Features
S 6V to 36V Input Range
S 5V at Up to 5A Output
S 400kHz Switching Frequency
S Selectable Forced Fixed-Frequency PWM Mode,
SKIP Mode, or External Synchronization
S Power-Good LED Indicator
S Enable Input
S Cycle-by-Cycle Current Limit and Thermal
Protection
S Proven PCB Layout
S Fully Assembled and Tested
DESIGNATION QTY DESCRIPTION
BIAS, EN, FSYNC,
OUT (x2),
SUP (x2)
7 Red multipurpose test points
C1 1
0.22FF Q10%, 50V X7R
ceramic capacitor (0805)
Murata GRM21BR71H224K
C2 1
47FF Q20%, 50V electrolytic
capacitor (D8)
Panasonic EEE-FK1H470XP
C4 1
0.1FF Q10%, 50V X7R ceramic
capacitor (0603)
Murata GRM188R71H104K
C5, C9 0 Not installed, ceramic
capacitors (0603)
C6 1
100FF Q20%, 6.3V X5R
ceramic capacitor (1210)
TDK C3325X5R0J107M
C7 1
47FF Q20%, 6.3V X7R ceramic
capacitor (1210)
Murata GRM32ER70J476M
C8 1
1FF Q10%, 16V X7R ceramic
capacitor (0603)
Murata GRM188R71C105K
C10 1
6800pF Q10%, 50V X7R
ceramic capacitor (0603)
Murata GRM188R71H682K
DESIGNATION QTY DESCRIPTION
C11 1
4.7FF Q10%, 50V X7R ceramic
capacitor (1206)
Murata GRM31CR71H475K
C13 1
4.7FF Q10%, 50V X7R ceramic
capacitor (1210)
Murata GRM32ER71H475K
D1 1 60V, 3A Schottky diode (SMB)
Diodes Inc. B360B-13-F
D2 1 Red LED (0603)
D3 0 Not installed, Schottky diode
(3 SOT23)
JU1 1 3-pin header
JU2 1 2-pin header
L1 1 5.5FH Q20%,10A inductor
Würth 744325550
N1 1
40V, 6A dual n-channel
MOSFET (8 SO)
Fairchild FDS8949
PGND (x5),
SGND 6 Black multipurpose test points
R2, R5, R6 0 Not installed, resistors (0603)
R4 1
0.015I Q1%, 1/2W resistor
(1206)
IRC LRF1206LF-01-R015-F
R7, R12 2 0I Q5% resistors (0603)
R8 1 66.5kI Q1% resistor (0603)
MAX16955 Evaluation Kit
Evaluates: MAX16955
_________________________________________________________________ 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.
Component List
19-5772; Rev 1; 1/12
Ordering Information appears at end of data sheet.
DESIGNATION QTY DESCRIPTION
R9 1 13kI Q1% resistor (0603)
R10 1 10kI Q5% resistor (0603)
R11 1 51.1kI Q1% resistor (0603)
U1 1
Synchronous buck converter
(16 TSSOP-EP)
Maxim MAX16955AUE/V+
SUPPLIER PHONE WEBSITE
Diodes Incorporated 805-446-4800 www.diodes.com
Fairchild Semiconductor 888-522-5372 www.fairchildsemi.com
IRC, Inc. 361-992-7900 www.irctt.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
Würth Electronik GmbH & Co. KG 201-785-8800 www.we-online.com
DESIGNATION QTY DESCRIPTION
— 2 Shunts
— 1 PCB: MAX16955 EVALUATION
KIT
_________________________________________________________________ Maxim Integrated Products 2
MAX16955 Evaluation Kit
Evaluates: MAX16955
Quick Start
Required Equipment
• MAX16955 EV kit
• 12V, 1A power supply
•
An electronic load capable of sinking 1A (e.g.,HP6060B)
• Two digital voltmeters (DVMs)
Procedure
The EV kit is fully assembled and tested. Follow the steps
below to verify board operation:
1) Verify that a shunt is installed across pins 2-3 on
jumper JU1.
2) Verify that a shunt is not installed across jumper JU2
(output enabled).
3) Connect the load across the OUT and PGND test
points.
4) Connect the first DVM across the SUP and PGND test
points.
5) Connect the second DVM across the OUT and PGND
test points.
6) Connect the power supply’s positive and ground
terminals to the SUP and PGND test points,
respectively.
7) Turn on the power supply and set to 12V with a 1A
current limit.
8) Enable the 1A electronic load.
9) Verify that the red LED (D2) is off and the DVM at OUT
measures 5V.
Detailed Description of Hardware
The MAX16955 EV kit is a fully assembled and tested
PCB that contains all the components neces sary to
evaluate the performance of the MAX16955 synchronous
PWM step-down controller. The device is available in a
16-pin TSSOP package and features an exposed pad for
thermal dissipation. The device has a 3.5V to 36V input
voltage range. The EV kit circuit is designed to operate
from a single DC power supply ranging from 6V to 36V.
The EV kit is configured to output 5V and provides up to
5A load current at the OUT and PGND test points. The
switching frequency is set to 400kHz using resistor R8.
The peak inductor current is set to 5.3A using resistor
R4. The EV kit can be configured to operate in forced
fixed-frequency PWM mode, low-quiescent current SKIP
mode, or external synchroniza tion using jumper JU1. The
EV kit features test points to evaluate the enable (EN)
feature and to monitor the BIAS output volta ge. A
red LED (D2) is available to monitor the power-good
(PGOOD) output signal.
Component Suppliers
Component List (continued)
Note: Indicate that you are using the MAX16955 when contacting these component suppliers.
JUMPER SHUNT
POSITION DESCRIPTION
JU1
1-2 Connects FSYNC to VBIAS to enable continuous PWM mode.
2-3* Connects FSYNC to AGND to enable SKIP mode under light-load conditions.
Open When FSYNC is unconnected, or when a clock source is present, continuous PWM mode is
enabled. SYNC can be used to synchronize with other supplies when a clock source is present.
JU2 Closed Connects EN to AGND (shutdown).
Open* Connects EN to VSUP through a pullup resistor (normal operation).
_________________________________________________________________ Maxim Integrated Products 3
MAX16955 Evaluation Kit
Evaluates: MAX16955
Table 1. Jumper Descriptions (JU1, JU2)
*Default position.
Modes of Operation (JU1)
Jumper JU1 configures the EV kit for external synchroni-
zation, forced fixed-frequency PWM, or SKIP mode oper-
ation. Install a shunt across pins 1-2 on JU1 to operate
the EV kit in forced fixed-frequency PWM mode. Place a
shunt across pins 2-3 on JU1 to operate in SKIP mode.
Remove the shunt on JU1 when synchronizing, using an
external digital clock signal at the FSYNC and SGND test
points. Refer to the Forced Fixed-Frequency PWM Mode
and Light-Load Low-Quiescent Operating (SKIP) Mode
sections in the MAX16955 IC data sheet for additional
information. See Table 1 for JU1 configuration.
For external synchronization, apply a digital signal at the
FSYNC and SGND test points with a frequency between
220kHz and 1.1MHz. For proper frequency synchroniza-
tion, FSYNC’s input frequency must be at least 110% of
the EV kit’s programmed internal oscillator frequency.
When FSYNC is driven with an external digital clock, the
device synchronizes to the rising edge of the external
clock. The digital square-wave clock source at FSYNC
must provide the following signal qualities:
• 0 to 0.4V logic-low
• 1.4V to 5.5V logic-high
• 220kHz to 1.1MHz input frequency
• 100ns minimum pulse width
Enable Control (JU2)
The EV kit output is enabled through pullup resistor R11
when the power source applied between the SUP and
PGND test points is greater than 1.8V. To enable the EV
kit output, remove the shunt on jumper JU2. To disable
the EV kit output, install a shunt on JU2. See Table 2 for
JU2 configuration. If the EN pin is toggled from low to
high, the switching regulator shuts down and remains off
until the output voltage decays to 1.25V. At that point the
EV kit output turns on using the soft-start sequence.
Switching Frequency
The controller’s approximate switching frequency is set
to 400kHz by resistor R8. Replace resistor R8 with a new
resistor value to set the switching frequency between
220kHz and 1MHz. Refer to the Setting the Switching
Frequency section in the MAX16955 IC data sheet for
selecting R8 when reconfiguring the EV kit switching
frequency. When reconfiguring the EV kit switching
frequency, it is necessary to replace the compensa-
tion network components C9, C10, R9, and power
components. Refer to the Design Procedure section in
the MAX16955 IC data sheet for computing new com-
pensation and power component values.
Configuring the Output Voltage (OUT)
The EV kit step-down controller’s output voltage (OUT) is
configured to 5V. OUT can be reconfigured between 1V
and 10V by removing resistor R7 and inserting feedback
resistors at the R5 and R6 (0603) PCB pads. To configure
the EV kit’s output voltage, refer to the Setting the Output
Voltage section in the MAX16955 IC data sheet for
instructions on selecting resistor values. Also refer to the
Effective Input-Voltage Range and Output Capacitor sec-
tions in the MAX16955 IC data sheet. Refer to the Design
Procedure section in the MAX16955 IC data sheet and
modify the compensation network accordingly.
Power-Good Indicator (D2)
The EV kit provides a red LED power-good indicator (D2)
to monitor undervoltage and overvoltage conditions at
OUT. D2 illuminates when OUT falls below 90% (typ) or
rises above 111% (typ) of its nominal regulated voltage.
Peak Inductor Current Limit
The device’s current-limit circuit uses differential current-
sense inputs (CS and OUT) to limit the peak inductor
current. The EV kit peak inductor current is set to 5.3A
using resistor R4. Use the following equation to calculate
the resistance needed to reconfigure the inductor peak
current limit:
ILIM
80mV
R4 I
=
where R4 is in milliohms and IILIM is the peak inductor
current in amps.
_________________________________________________________________ Maxim Integrated Products 4
MAX16955 Evaluation Kit
Evaluates: MAX16955
Figure 1. MAX16955 EV Kit Schematic
1.0” 1.0”
1.0”
_________________________________________________________________ Maxim Integrated Products 5
MAX16955 Evaluation Kit
Evaluates: MAX16955
Figure 2. MAX16955 EV Kit Component Placement Guide—
Component Side
Figure 3. MAX16955 EV Kit PCB Layout—Component Side
Figure 4. MAX16955 EV Kit PCB Layout—VCC Layer 2
1.0” 1.0”
1.0”
_________________________________________________________________ Maxim Integrated Products 6
MAX16955 Evaluation Kit
Evaluates: MAX16955
Figure 6. MAX16955 EV Kit PCB Layout—Solder Side
Figure 5. MAX16955 EV Kit PCB Layout—PGND and SGND
Layer 3
Figure 7. MAX16955 EV Kit Component Placement Guide—
Solder Side
PART TYPE
MAX16955EVKIT# EV Kit
_________________________________________________________________ Maxim Integrated Products 7
MAX16955 Evaluation Kit
Evaluates: MAX16955
Ordering Information
#Denotes RoHS compliant.
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 2/11 Initial release —
1 1/12 Changed VOUT max from 12V to 10V in the Configuring the Output Voltage
(OUT) section to match the IC data sheet 3
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 8
© 2012 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX16955 Evaluation Kit
Evaluates: MAX16955
Revision History
