MAX1833 Maxim, MAX1833 Datasheet - Page 9

• Manufacturer Part Number: MAX1833
• Description: High-Efficiency Step-Up Converters with Reverse Battery Protection
• Manufacturer: Maxim

sometimes cause false shutdowns. To minimize the effect
of ripple, connect a low-value capacitor (C1) from SHDN
to GND to filter out input noise. Select a C1 value such
that the R4
The MAX1833/MAX1835 provide a power-on reset out-
put (RST). A 100kΩ to 1MΩ pullup resistor from RST to
OUT provides a logic control signal. This open-drain
output pulls low when the output is 10% below its regu-
lation point. If not used, connect it to GND.
The output voltage of the MAX1832/MAX1834 is
adjustable from +2V to +5.5V, using external resistors
R1 and R2 (Figure 1b). Since FB leakage is 20nA
(max), select feedback resistor R1 to be 100kΩ to
1MΩ. Calculate R2 as follows:
to prevent the maximum current limit (525mA) from being
reached before the maximum on-time (5µs) expires.
For maximum output current, choose L such that:
where R
is the R
Choose an output capacitor to achieve the desired out-
put ripple percentage.
where r is the desired output ripple in %. A 10µF ceramic
capacitor is a good starting value. The input capacitor
where V
The control scheme of the MAX1832–MAX1835 permits
flexibility in choosing an inductor. A 10µH inductor per-
forms well for most applications, but values from 4.7µH to
100µH may also be used. Small inductance values typi-
cally offer smaller physical size. Large inductance values
minimize output ripple but reduce output power. Output
power is reduced when the inductance is large enough
I
OUT MAX
(
DS(ON)
FB
IND
V
)
BATT MAX
=
✕
= 1.228V.
0 525
is the inductor series resistance, and R
C1 time constant is above 2ms.
0 525
.
C
.
(
2
of the N-channel MOSFET (0.4Ω typ).
OUT
R
A
2
High-Efficiency Step-Up Converters with
_______________________________________________________________________________________
A
)
=
×
>
( )
Setting the Output Voltage
1
R
V
µ
0 5
BATT MIN
1
s
.



V
r
< <
×
%
V
OUT
(
FB
L
L
×
Capacitor Selection
×
V
)
V
−
Inductor Selection
OUT
−
BATT MIN
0 525
1
.
0 525



Power-On Reset
.
V
0 525
2
OUT
2
.
(
A
A
2
)
A
(
R
(
5
NCH
µ
s
)
+
R
Reverse Battery Protection
IND
NCH
)
reduces the peak current drawn from the battery and
can be the same value as the input capacitor. A larger
input capacitor can be used to further reduce ripple and
improve efficiency.
Careful printed circuit layout is important for minimizing
ground bounce and noise. Keep the IC’s GND pin and
the ground leads of the input and output filter capaci-
tors less than 0.2in (5mm) apart. In addition, keep all
connections to the FB and LX pins as short as possible.
In particular, when using external feedback resistors,
locate them as close to FB as possible. To maximize
output power and efficiency and minimize output ripple
voltage, use a ground plane and solder the IC’s GND
directly to the ground plane.
TRANSISTOR COUNT: 953
PROCESS: BiCMOS
Table 1. Suggested Inductors and
Suppliers
Table 2. Suggested Surface-Mount
Capacitors and Manufacturers
VALUE
MANUFACTURER
4.7 to
4.7 to
4.7 to
(µF)
47
10
22
Coilcraft
Sumida
Murata
DESCRIPTION
series tantalum
series tantalum
X7R ceramic
X7R ceramic
594/595 D-
TAJ, TPS-
PC Board Layout and Grounding
CDRH4D18-100
DS1608C-103
DO1606T-103
LQH4N100K
INDUCTOR
CR43-100
FACTURER
Taiyo Yuden
Chip Information
Sprague
MANU-
AVX
TDK
847-639-6400
847-956-0666
814-237-1431
603-224-1961
803-946-0690
847-390-4373
408-573-4150
PHONE
PHONE
9