Rainbow Electronics MAX749 - Manual (Page 4)

MAX749
Digitally Adjustable LCD Bias Supply
4 ______________________________________________________________________________________
PIN NAME FUNCTION
1 V+
+2V to +6V Input Voltage to power the MAX749 and external circuitry. When using an external
P-channel MOSFET, V+ must exceed the MOSFET’s gate threshold voltage.
2 ADJ
Logic Input. When CTRL is high, a rising edge on ADJ increments an internal counter. When CTRL is
low, the counter is reset to mid-scale when ADJ is high. When ADJ is low, the counter does not
change (regardless of activity on CTRL) as long as V+ is applied.
3 CTRL
Logic Input. When CTRL and ADJ are low, the MAX749 is shut down, but the counter is not reset.
When CTRL is low, the counter is reset to mid-scale when ADJ is high. The device is always on when
CTRL is high.
4 FB
Feedback Input for output full-scale voltage selection. -V OUT(MAX) = (R FB ) x (20µA) where R FB is
connected from FB to -V OUT . The device is in regulation when V FB = 0V.
5 GND Ground
6 DLOW
Output Driver Low. Connect to DHI when using an external P-channel MOSFET. When using an
external PNP transistor, connect a resistor R
BASE from DLOW to the base of the PNP to set the maxi-
mum base-drive current.
7 DHI
Output Driver High. Connect to the gate of the external P-channel transistor, or to the base of the
external PNP transistor.
8 CS
Current-Sense Input. The external transistor is turned off when current through the sense resistor,
R
SENSE , brings CS below V+ by 140mV (typ).
OUTPUT
VOLTAGE
LOAD
CURRENT
100mV AC /div
10mA/div
0mA
LOAD-TRANSIENT RESPONSE
V OUT = -15V
TRANSISTOR = ZTX750
50 µ s/div
V OUT = -15V
TRANSISTOR = ZTX750
OUTPUT
VOLTAGE
INPUT
VOLTAGE
100mV AC /div
1 V/div
0V
LINE-TRANSIENT RESPONSE
V OUT = -15V
I LOAD = 5mA
TRANSISTOR = ZTX750
50ms/div
____________________________Typical Operating Characteristics (continued)
(T A = +25°C, L = 47µH, unless otherwise noted.)
______________________________________________________________Pin Description