MAX5092EVKIT+ Maxim Integrated Products, MAX5092EVKIT+ Datasheet - Page 19

• Manufacturer Part Number: MAX5092EVKIT+
• Description: KIT EVALUATION FOR MAX5092
• Manufacturer: Maxim Integrated Products

Specifications of MAX5092EVKIT+

• Main Purpose: DC/DC, Step Up with LDO
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 5V
• Current - Output: 250mA
• Voltage - Input: 4 ~ 72V
• Regulator Topology: Buck-Boost
• Board Type: Fully Populated
• Utilized Ic / Part: MAX5092B
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The MAX5092_/MAX5093_ feature Dual Mode™ opera-
tion for the internal boost converter output voltage.
These devices operate in a preset output-voltage mode
or an adjustable output-voltage mode. In preset mode,
internal trimmed feedback resistors set V
fixed 7V. Select the preset mode by directly connecting
BSFB to SGND (Figures 4 and 5). Ensure a low-imped-
ance path between BSFB and SGND to limit the tran-
sient at BSFB to below 100mV. In adjustable mode,
connect BSFB to the center tap of an external resistor-
divider connected between BSOUT and SGND to pro-
gram V
V
the current drawn by the resistor-divider at BSOUT
adds to the quiescent current and the shutdown current
of the IC. Use the resistor-divider only if V
required to be significantly different than 7V. Select
499kΩ or lower resistance value for the bottom resistor
(R2) of the divider connected to SGND. The top resistor
(R1) value is calculated as:
where V
typ) and V
BSOUT.
The LDO output voltage is also Dual Mode (preset and
adjustable). Preset mode is selected by connecting
SET to SGND (Figures 4 and 5). In preset mode, V
regulates to 3.3V (MAX5092A/MAX5093A) or 5V
(MAX5092B/MAX5093B) by internal trimmed feedback
resistors. Adjustable mode is selected by connecting
SET to the center tap of an external resistor-divider
connected between OUT and SGND (Figures 6 and 7).
Note that the current drawn by the resistor-divider at
OUT adds to the quiescent current of the LDO. Use the
resistor-divider only if V
cantly different than the preset voltage. Select 100kΩ or
lower value for the bottom resistor (R5) of the divider
connected to SGND. The top resistor (R4) value is cal-
culated as:
where V
and V
output.
OUT
4V to 72V Input LDOs with Boost Preregulator
Setting the LDO Output Voltage (V
OUT
+ V
BSOUT
SET
BSFB
BST_DIS
is the desired output voltage for the LDO
BSOUT
is the regulation voltage at SET (1.24V typ)
is the regulation voltage at BSFB (1.24V
(Figures 6 and 7). Program (V
R
R
1
) for lower V
______________________________________________________________________________________
4
=
is the desired output voltage for
=
R
2
R
Output Voltage (V
5
×
OUT
×
⎛
⎜
⎝
V
⎛
⎜
⎝
V
BSOUT
V
V
BSFB
OUT
SET
is required to be signifi-
BSOUT
Setting the Boost
−
−
1
1
⎞
⎟
⎠
⎞
⎟
⎠
ripple. Note that
BSOUT
BSOUT
BSOUT
BSOUT
OUT
to a
OUT
is
<
)
)
The MAX5093_ requires an external diode connected
between LX and BSOUT (Figures 5 and 7). Proper
selection of an external diode can offer a lower forward-
voltage drop and a higher reverse-voltage handling
capability. Since the high switching frequency of the IC
demands a high-speed rectifier, Schottky diodes are
recommended for most applications because of their
fast recovery time and low forward-voltage drop.
Ensure that the diode’s peak current rating is greater
than or equal to the peak current limit of internal boost
converter MOSFET. A diode average forward current
rating of at least 1A is recommended. Additionally, the
diode reverse breakdown voltage must be greater than
the worst-case load-dump-condition voltage.
The MAX5092_/MAX5093_ contain an open-drain
power-on-reset output (RESET) that indicates when the
LDO output voltage (V
V
RESET goes high impedance after a user-programma-
ble time delay. This time duration is programmable by a
capacitor (C
chosen RESET active timeout period (t
the required capacitor value as:
When V
tion voltage, a 5mA pulldown current from CT to SGND
discharges C
determines the delay necessary to pull RESET low. This
delay provides glitch immunity to the RESET function.
The glitch immunity delay is directly proportional to the
CT capacitor and is approximately 70µs for a 0.1µF
capacitor at CT.
Dual Mode is a trademark of Maxim Integrated Products, Inc.
OUT
rises above 92% of the nominal output voltage,
Schottky Diode Selection (MAX5093_)
OUT
drops below 90% of the LDO output regula-
CT
CT
) from CT to SGND (Figures 4–7). For a
C
. The time required to discharge CT
CT
=
2 10
OUT
×
CT Capacitor Selection
) is out of regulation. When
−
1 24
6
.
×
t
DELAY
DELAY
), calculate
19