MAX16955EVKIT+ Maxim Integrated Products, MAX16955EVKIT+ Datasheet - Page 3

• Manufacturer Part Number: MAX16955EVKIT+
• Description: Power Management Modules & Development Tools MAX16955 EVAL KIT MAX16955 EVAL KIT
• Manufacturer: Maxim Integrated Products

Specifications of MAX16955EVKIT+

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 1. Jumper Descriptions (JU1, JU2)
*Default position.
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
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.
The controller’s approximate switching frequency is set
to 400kHz by resistor R8. Replace resistor R8 with a new
JUMPER
JU1
JU2
POSITION
_________________________________________________________________ Maxim Integrated Products 3
SHUNT
Closed
Open*
Open
2-3*
1-2
Modes of Operation (JU1)
Connects FSYNC to V
Connects FSYNC to AGND to enable SKIP mode under light-load conditions.
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.
Connects EN to AGND (shutdown).
Connects EN to V
Switching Frequency
Enable Control (JU2)
SUP
BIAS
through a pullup resistor (normal operation).
to enable continuous PWM mode.
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.
The EV kit step-down controller’s output voltage (OUT) is
configured to 5V. OUT can be reconfigured between 1V
and 12V 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.
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.
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:
where R4 is in milliohms and I
current in amps.
DESCRIPTION
Evaluates: MAX16955
Configuring the Output Voltage (OUT)
Peak Inductor Current Limit
R4
Power-Good Indicator (D2)
=
80mV
I
ILIM
ILIM
is the peak inductor