MAX1605 Maxim, MAX1605 Datasheet - Page 7

• Manufacturer Part Number: MAX1605
• Description: 30V Internal Switch LCD Bias Supply
• Manufacturer: Maxim

Adjust the output voltage by connecting a voltage-
divider from the output (V
R2 between 10kΩ to 200kΩ. Calculate R1 with the fol-
lowing equation:
where V
30V. The input bias current of FB has a maximum value
of 100nA, which allows large-value resistors to be used.
For less than 1% error, the current through R2 should
be greater than 100 times the feedback input bias cur-
rent (I
The MAX1605 allows a selectable inductor current limit
of 125mA, 250mA, or 500mA (Figure 2). This allows
flexibility in designing for higher current applications or
for smaller, compact designs. The lower current limit
allows the use of a physically smaller inductor in space-
sensitive, low-power applications. Connect LIM to V
for 500mA, leave floating for 250mA, or connect to
GND for 125mA.
Pull SHDN low to enter shutdown. During shutdown, the
supply current drops to 0.1µA and LX enters a high-
impedance state. However, the output remains con-
nected to the input through the inductor and output
rectifier, holding the output voltage to one diode drop
below V
itance and load at OUT determine the rate at which
V
regardless of the input and output voltages.
Figure 2. Setting the Peak Inductor Current Limit
OUT
FB
decays. SHDN can be pulled as high as 6V,
IN
(2.4V TO 5.5V)
).
FB
when the MAX1605 is shut down. The capac-
V
= 1.25V and V
CC
R1 = R2 [(V
Setting the Output Voltage (FB)
Current Limit Select Pin (LIM)
_______________________________________________________________________________________
V
GND
LIM
CC
I PEAK = 500mA
MAX1605
OUT
OUT
30V Internal Switch LCD Bias Supply
OUT
) to FB (Figure 3). Select
/ V
may range from V
Shutdown ( SHDN )
FB
) – 1]
NO CONNECTION
(2.4V TO 5.5V)
V
CC
IN
CC
to
V
GND
LIM
CC
I PEAK = 250mA
MAX1605
Separate voltage sources can supply the inductor (V
and the IC (V
batteries as well as high-voltage sources (0.8V to 30V)
because chip bias is provided by a logic supply (2.4V
to 5.5V), while the output power is sourced directly from
the battery to L1. Conversely, V
supplied from one supply if it remains within V
operating limits (+2.4V to +5.5V).
Figure 3. Typical Application Circuit
ON
V
V
0.1µF
CC
IN
C1
= 0.8V TO V
= 2.4V TO 5.5V
Separate/Same Power for L1 and V
OFF
10µF
C
OUT
CC
IN
). This allows operation from low-voltage
V
SHDN
LIM
CC
MAX1605
(2.4V TO 5.5V)
10µH
L1
V
CC
GND
LX
FB
IN
LIM
GND
2.2MΩ
V
165kΩ
CC
and V
I PEAK = 125mA
D1
R1
R2
MAX1605
V
OUT
CC
= 18V
can also be
10pF
C
FF
CC
C
1µF
OUT
CC
IN
’s
7
)