MAX5028EUT+T Maxim Integrated Products, MAX5028EUT+T Datasheet - Page 9

• Manufacturer Part Number: MAX5028EUT+T
• Description: IC DC-DC CONV PWM SOT23-6
• Manufacturer: Maxim Integrated Products
• Type: Step-Up (Boost)r

Specifications of MAX5028EUT+T

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 3 ~ 36 V
• Current - Output: 40mA
• Frequency - Switching: 500kHz
• Voltage - Input: 3 ~ 11 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-6
• Power - Output: 695.7mW
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: MAX5028EUT+T; MAX5028EUT+TTR

where V
If the boost converter remains in the discontinuous
mode of operation, then the approximate peak inductor
current, I
where T
is the input voltage, I
the efficiency of the boost converter.
Table 1. Inductor Vendors
Figure 1. Functional Diagram
Coilcraft
Sumida
Toko
3
2
5
FB
REF
GND
V
CC
REF
S
VENDOR
LPEAK
I
LPEAK
is the period, V
Determining Peak Inductor Current
is 1.25V
-A
+A
+C
-C
, is represented by the formula below:
ULVO
R
MAIN PWM
COMPARATOR
=
1
_______________________________________________________________________________________
=
CURRENT-
LIMIT
COMPARATOR
OUT
R
2
2
T
S
⎛
⎜
⎝
OUT
is the output current, and η is
V
V
(
OUT
REF
V
OSCILLATOR
OUT
CONTROL
is the output voltage, V
LOGIC
847-639-6400
847-545-6700
847-297-0070
-
η
1
L
⎞
⎟
⎠
−
PHONE
V
MAX5025
MAX5026
IN OUT
)
SHUTDOWN
I
THERMAL
N
SHDN
PGND
LX
500kHz, 36V Output, SOT23,
4
6
1
IN
Step-Up DC-DC Converters
847-639-1469
847-545-6720
847-699-7864
47µH is the recommended inductor value when the out-
put voltage is 30V and the input voltage is 5V. In gener-
al, the inductor should have a current rating greater
than the current-limit value. For example, the inductor’s
current rating should be greater than 150mA to support
a 4mA output current. Equivalent series resistance
(ESR) should be below 1Ω for reasonable efficiency.
Due to the MAX5025–MAX5028’s high switching fre-
quency, inductors with a ferrite core or equivalent are
recommended. Powdered iron cores are not recom-
mended due to their high losses at frequencies over
500kHz. Table 1 shows a list of vendors and 47µH
inductor parts.
For 4mA output current and output voltages other than
30V, the inductor can be simply scaled in value
according to the following formula:
Use the following formula to calculate the upper bound
of the inductor value at different output voltages and
output currents. This is the maximum inductance value
for discontinuous mode operation.
Calculate the lower bound, L
inductance value using the following formula, which will
allow the maximum output current to be delivered with-
out reaching the peak current limit:
Notice that the switch current limit, (V
function of the input voltage, V
the inductor should be greater than the switch current
limit.
FAX
L
LOWER
L
UPPER
Determining the Inductor Value
L
DT1608C-473
CDRH4D28-470
A915BY-470M
=
=
=
PART NUMBER OF 47µH INDUCTOR
(
V
47
2
IN
2
T
η
μ
(
S
2
H V
V
⎛
⎜
⎝
OUT
I
)
OUT
(
(
V
V
25
(
5
IN
OUT
LOWER
OUT
V
−
V
(
IN
)
V
260
OUT
2
IN
−
. The current rating of
−
)
V
V
mA
T
, for the acceptable
IN OUT
IN
S
IN
)
η
)
)
I
⎞
⎟
⎠
/5)(260mA), is a
2
9