MAX8654EVKIT+ Maxim Integrated, MAX8654EVKIT+ Datasheet - Page 3

• Manufacturer Part Number: MAX8654EVKIT+
• Description: Power Management IC Development Tools MAX8654 Eval Kit
• Manufacturer: Maxim Integrated
• Type: DC/DC Converters, Regulators & Controllersr
• Series: MAX8654r

Specifications of MAX8654EVKIT+

• Rohs: yes
• Product: Evaluation Kits
• Tool Is For Evaluation Of: MAX8654
• Input Voltage: 4.5 V to 14 V
• Output Voltage: 0.6 V to 0.85 V
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Output Current: 8 A
• For Use With: MAX8654

The switching frequency in fixed-frequency PWM oper-
ation is resistor-programmable from 250kHz to 1.2MHz.
Set the switching frequency of the IC with a resistor
(R
where f
The UVLO circuitry inhibits switching when V
is below 4.4V (V
(V
olds, UVLO clears and the soft-start function activates.
A 100mV hysteresis is built in for glitch immunity.
PWRGD is an open-drain output that goes high imped-
ance once the soft-start ramp has concluded, provided
V
when V
is less than 0.54V. PWRGD is low during shutdown.
The MAX8654 features a SYNC function that allows the
switching frequency to be synchronized to any external
clock frequency that is higher than the internal clock
frequency. Drive SYNC with a square wave at the
desired synchronization frequency. A rising edge on
SYNC triggers the internal SYNC circuitry. Connect
SYNC to GND to disable the function and operate with
the internal oscillator. The SYNCOUT output generates
a clock signal that is 180° out-of-phase with its internal
oscillator, or the signal applied to SYNC. This allows for
another MAX8654 to be synchronized 180° out-of-
phase to reduce the input ripple current.
FB
VL
FREQ
Detailed Description of Hardware
and V
rising). Once these voltages are above the thresh-
S
) from FREQ to GND. R
FB
is the desired switching frequency in megahertz.
falls below 0.54V for at least 50µs or V
R
REFIN
FREQ
Undervoltage Lockout (UVLO)
IN
are above 0.54V. PWRGD pulls low
_______________________________________________________________________________________
=
, V
52 36
Evaluating Other Switching
VDL
.
×
rising) or V
⎛
⎜
⎝
Power Good (PWRGD)
f
1
SYNC and SYNCOUT
s
Frequencies (FREQ)
FREQ
−
0 05
.
is calculated as:
μ
VL
s k
⎞
⎟ Ω
⎠
is below 3.1V
IN
or V
REFIN
VDL
MAX8654 Evaluation Kit
The MAX8654 utilizes an adjustable soft-start function
to limit inrush current during startup. An 8µA (typ) cur-
rent source charges an external capacitor (C3) con-
nected to SS to increase the capacitor voltage in a con-
trolled manner. The soft-start time is adjusted by the
value of the external capacitor from SS to GND. The
required capacitance value is determined as:
where t
The MAX8654 also features an external reference input
(REFIN). The IC regulates FB to the voltage applied to
REFIN. The internal soft-start is not available when
using an external reference. A method of soft-start
when using an external reference is shown in the
MAX8654 data sheet. Connect REFIN to SS to use the
internal 0.6V reference (jumper JU3).
Drive EN high by placing a shunt on JU1 to turn on the
IC. To shut down the IC and reduce quiescent current
to 10µA (typ), remove the shunt on JU1. During shut-
down, the outputs of the MAX8654 are high impedance.
Place a shunt on jumper JU2 to connect SYNC to GND.
Place a shunt on pins 1-2 of JU3 to connect the REFIN
pin to the SS pin. When using an external reference,
place a shunt on pins 2-3 of jumper JU3.
The MAX8688 is a fully digital power-supply manager
that can be tested in conjunction with the MAX8654.
Samples of the MAX8688 IC can be ordered from
Maxim. To test the MAX8688, populate it with its circuit-
ry, as shown by the schematic or in the component list.
Also, place a shunt on pins 2-3 of JU3. For further infor-
mation, refer to the MAX8688 IC data sheet.
SS
is the required soft-start time in seconds.
C
=
Evaluating the MAX8688
8
μ ×
0 6 .
A t
Soft-Start and REFIN
V
ss
Jumper JU1 Function
Jumper JU2 Function
Jumper JU3 Function
Jumper Settings
3