MAX1745EUB+T Maxim Integrated Products, MAX1745EUB+T Datasheet - Page 12

• Manufacturer Part Number: MAX1745EUB+T
• Description: IC DC-DC CNTRLR STP DWN 10UMAX
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX1745EUB+T

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.25 ~ 18 V
• Frequency - Switching: 330kHz
• Voltage - Input: 4.5 ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Power - Output: 444mW
• Output Voltage: 1.25 V to 18 V
• Output Current: 10 A
• Input Voltage: 4.5 V to 36 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

High-Voltage, Step-Down DC-DC
Controllers in µMAX
Table 1. Component Suppliers
The MAX1744/MAX1745’s high switching frequency
demands a high-speed rectifier. Schottky diodes, such
as the 1N5817–1N5822 family or surface-mount equiva-
lents, are recommended. Ultra-high-speed rectifiers
with reverse recovery times around 50ns or faster
should be used for high output voltages, where the
increased forward drop causes less efficiency degra-
dation. Make sure that the diode’s peak current rating
exceeds the peak current limit set by R
its breakdown voltage exceeds V
are preferred for heavy loads due to their low forward
voltage, especially in low-voltage applications. For
high-temperature applications, some Schottky diodes
may be inadequate due to their high leakage currents.
In such cases, ultra-high-speed rectifiers are recom-
mended, although a Schottky diode with a higher
reverse voltage rating can often provide acceptable
performance.
12
COMPANY
AVX
Coilcraft
Coiltronics
Dale/Vishay
Kemet
Inter nati onal
Recti fi er
IRC
Motorola
Nichicon
Nihon
Sanyo
Siliconix
Sprague
Sumida
United
Chemi-Con
______________________________________________________________________________________
COUNTRY
Japan
Japan
Japan
Japan
USA
USA
USA
USA
USA
USA
USA
USA
USA
USA
USA
USA
USA
USA
USA
81- 7- 5231- 8461
81- 3- 3494- 7411
81- 7- 2070- 6306
81- 3- 3607- 5111
803-946-0690
800-282-4975
847-639-6400
516-241-7876
402-564-3131
408-986-0424
310-322-3331
512-992-7900
602-303-5454
408-988-8000
800-554-5565
603-224-1961
714-255-9500
847- 843- 7500
805- 867- 2555
619- 661- 6835
847- 956- 0666
PHONE
or
or
Diode Selection
IN
. Schottky diodes
SENSE
81-7-5256-4158
81-3-3494-7414
81-7-2070-1174
81-3-3607-5144
803-626-3123
847-639-1469
516-241-9339
402-563-6418
408-986-1442
310-322-3332
512-992-3377
602-994-6430
847-843-2798
805-867-2698
619-661-1055
408-970-3950
603-224-1430
847-956-0702
714-255-9400
FAX
, and that
Choose filter capacitors to service input and output
peak currents with acceptable voltage ripple. ESR in
the output capacitor is a major contributor to output rip-
ple, so low-ESR capacitors are recommended. Low-
ESR tantalum, polymer, or ceramic capacitors are best.
Low-ESR aluminum electrolytic capacitors are tolera-
ble, but standard aluminum electrolytic capacitors are
not recommended.
Voltage ripple is the sum of contributions from ESR and
the capacitor value:
For tantalum capacitors, the ripple is determined by the
ESR, but for ceramic capacitors, the ripple is mostly
due to the capacitance. Voltage ripple as a conse-
quence of ESR is approximated by:
The ripple due to the capacitance is approximately:
Estimate input and output capacitor values for given
voltage ripple as follows:
where I
These equations are suitable for initial capacitor selec-
tion; final values should be set by testing a prototype or
evaluation kit. When using tantalum capacitors, use
good soldering practices to prevent excessive heat
from damaging the devices and increasing their ESR.
Also, ensure that the tantalum capacitors’ surge-current
ratings exceed the startup inrush and peak switching
currents.
Pursuing output ripple lower than the error compara-
tor’s hysteresis (0.6% of the output voltage) is not prac-
tical, since the MAX1744/MAX1745 will switch at slower
frequencies, increasing inductor ripple current thresh-
old. Choose an output capacitor with a working voltage
rating higher than the output voltage.
The input filter capacitor reduces peak currents drawn
from the power source and reduces noise and voltage
C
C
ΔL
IN
OUT
V
is the change in inductor current.
=
RIPPLE
V
V
RIPPLE,ESR
=
RIPPLE CIN IN
V
V
RIPPLE,C
RIPPL
1
2
LI
≈
,
2
V
Δ
E E COUT OUT
1
2
RIPPLE ESR
L
,
LI
V
≈
2
Δ
≈
L
(
R
,
V
ESR
Capacitor Selection
LI
2CV
2
)
PEAK
+
Δ
O
V
I p p
⎛
⎜
⎝
RIPPLE C
V
−
IN
V
−
IN
V
,
OUT
⎞
⎟
⎠