Rainbow Electronics MAX1606 - Manual (Page 6)

MAX1606
28V Internal Switch LCD Bias Supply
with True Shutdown
6 _______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1 BATT
Inductor Supply Voltage, 0.8V to 5.5V. Internally connected to the source of a P-channel
MOSFET used to isolate the output from the input during shutdown. Bypass with a 10
µF or
greater capacitor.
2 FB
Feedback Input. Connect to a resistive divider network between the output and GND to set the
output voltage between V
BATT and 28V. The feedback threshold is 1.25V.
3 V CC IC Supply Voltage, 2.4V to 5.5V. Bypass V CC to GND with a 1 µF or greater capacitor.
4 GND Ground
5 LX
Inductor Switching Connection. Internally connected to the drain of a 28V N-channel MOSFET.
LX is high impedance in shutdown.
6 LIM
Inductor Current-Limit Selection. Connect LIM to V CC for 500mA, leave LIM floating for 250mA,
or connect LIM to GND for 125mA.
7 SHDN
Active-Low Shutdown Input. A logic low shuts down the device and reduces the supply current
to 0.1
µA. When shutdown, the MAX1606 isolates the output from the input by turning off the P-
channel MOSFET between BATT and SW. Connect SHDN to V CC for normal operation.
8 SW
Isolation Switch Output, Inductor Connection. Internally connected to the drain of a P-channel
MOSFET used to isolate the output from the input during shutdown.
17.9V
18.1V
18V
2V
4V
A
B
6V
100 µs/div
LINE TRANSIENT
MAX1606 toc13
A: V
BATT
= V
CC
= 2.4V TO 5.5V, 2V/div
B: V OUT = 18V, R OUT = 3.6k Ω, 100mV/div
0
0
500mA
20V
10V
0
2V
4V
400 µs/div
SHUTDOWN WAVEFORM
MAX1606 toc15
A
B
C
A: V SHDN , 2V/div
B: V OUT , 10V/div, R
OUT = 1.8k Ω
C: I L1 , 500mA/div
Typical Operating Characteristics (continued)
(V
CC
= 3.3V, V
BATT
= 3.6V, L1 = 10µH, SHDN = LIM = V
CC
, V
OUT(NOM)
= 18V (Figure 3), T
A
= +25°C, unless otherwise noted.)
0
17.9V
500mA
18.1V
18V
0
10mA
40 µs/div
LOAD TRANSIENT
MAX1606 toc14
A: I OUT = 1mA TO 10mA, 10mA/div
B: V
OUT
= 18V, 100mV/div
C: I L1 , 500mA/div
A
B
C