MAX5027 MAXIM [Maxim Integrated Products], MAX5027 Datasheet - Page 10

• Manufacturer Part Number: MAX5027
• Description: 500kHz, 36V Output, SOT23, PWM Step-Up DC-DC Converters
• Manufacturer: MAXIM [Maxim Integrated Products]

500kHz, 36V Output, SOT23, PWM Step-Up
DC-DC Converters
For a design in which V
4mA, η = 0.5, and T
L
and
L
For a worst-case scenario in which V
= 29V, I
L
and
L
The choice of 47µH as the recommended inductance
value is reasonable given the worst-case scenario
above. In general, the higher the inductance, the lower
the switching noise. Load regulation is also better with
higher inductance.
The MAX5025–MAX5028’s high switching frequency
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 inductor current. Also, the
diode reverse breakdown voltage must be greater than
V
10
Table 2. Schottky Diode Vendors
Table 3. Capacitor Table
UPPER
LOWER
UPPER
LOWER
Murata
Taiyo Yuden
TDK
OUT
Comchip
Panasonic
ST-Microelectronics
Vishay-Telefunken
Zetex
______________________________________________________________________________________
. Table 2 lists diode vendors.
COMPANY
OUT
= 87µH
= 46µH
= 12µH.
= 9µH.
VENDOR
= 4.4mA, η = 0.5, and T
S
= 2µs,
IN
= 5V, V
814-237-1431
408-573-4150
847-803-6100
PHONE
Diode Selection
OUT
510-657-8671
408-942-2912
602-485-6100
402-563-6866
631-360-2222
S
IN
= 1.25µs,
PHONE
= 30V, I
= 4.75V, V
OUT
OUT
814-238-0490
408-573-4159
847-803-6296
=
FAX
The output filter capacitor should be 1µF or greater. To
achieve low output ripple, a capacitor with low ESR, low
ESL, and high capacitance value should be selected.
For very low output ripple applications, the output of the
boost converter can be followed by an RC filter to fur-
ther reduce the ripple. Figure 3 shows a 100Ω, 1µF fil-
ter used to reduce the switching output ripple to
1mVp-p.
X7R ceramic capacitors are better for this boost appli-
cation because of their low ESR and tighter tolerance
over temperature than the Y5V ceramic capacitors.
Table 3 below lists manufacturers of recommended
capacitors.
Bypass V
the IC as is practical.
The MAX5025–MAX5028 switch at high speed, man-
dating careful attention to layout for optimum perfor-
mance. Protect sensitive analog grounds by using a
star ground configuration. Minimize ground noise by
connecting GND, PGND, the input bypass-capacitor
ground lead, and the output-filter ground lead to a sin-
gle point (star ground configuration). Also, minimize
510-657-8921
408-946-9063
602-486-6102
402-563-6296
631-360-8222
FAX
CC
GRM42-2X7R105K050AD (1µF capacitor)
GRM32-1210R71C475R (4.7µF capacitor)
UMK325BJ105KH (1µF capacitor)
EMK316BJ475ML (4.7µF capacitor)
C3225X7R1H155K (1.5µF capacitor)
C3225X7R1H105K (1µF capacitor)
with a 4.7µF ceramic capacitor as close to
Applications Information
PART NUMBERS
Layout Considerations
CDBS1045
MA2Z785
TMMBAT48
BAS382
ZHCS500
Capacitor Selection
Output Filter Capacitor
PART NUMBERS
Input Capacitor