MAX1605 Maxim, MAX1605 Datasheet - Page 6

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

The MAX1605 compact, step-up DC-DC converter oper-
ates from a +2.4V to +5.5V supply. Consuming only
18µA of supply current, the device includes an internal
switching MOSFET with 1Ω on-resistance and selectable
current limit (Figure 1). During startup, the MAX1605
extends the minimum off-time, limiting initial surge cur-
rent. The MAX1605 also features a shutdown mode.
30V Internal Switch LCD Bias Supply
Figure 1. Functional Diagram
6
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PIN
1
2
3
4
5
6
V
IN
V
CC
= 0.8V TO V
ON
= 2.4V TO 5.5V
OFF
OUT
NAME
SHDN
GND
V
LIM
LX
FB
CC
Detailed Description
LIM
V
SHDN
CC
MAX1605
SHUTDOWN
Active-Low Shutdown Input. A logic low shuts down the device and reduces the supply current
to 0.1µA. Connect SHDN to V
IC Supply Voltage (+2.4V to +5.5V). Bypass V
Ground
Inductor Connection. The drain of an internal 30V N-channel MOSFET. LX is high impedance in
shutdown.
Inductor Current Limit Selection. Connect LIM to V
or connect LIM to GND for 125mA.
Feedback Input. Connect to a resistive-divider network between the output (V
the output voltage between V
LOGIC
CONTROL
AMPLIFIER
LOGIC
ERROR
IN
CC
and 30V. The feedback threshold is 1.25V.
for normal operation.
The MAX1605 features a minimum off-time, current-lim-
ited control scheme. The duty cycle is governed by a
pair of one-shots that set a minimum off-time and a
maximum on-time. The switching frequency can be up
to 500kHz and depends upon the load and input volt-
age. The peak current limit of the internal N-channel
MOSFET is pin selectable and may be set at 125mA,
250mA, or 500mA (Figure 2).
CURRENT
1.25V
LIMIT
FUNCTION
10µH
L1
CC
to GND with a 0.1µF or greater capacitor.
CC
for 500mA, leave LIM floating for 250mA,
N
GND
LX
FB
C
FF
Pin Description
Control Scheme
V
OUT
OUT
R2
R1
= V
) and FB to set
IN
TO 30V
C
OUT