Rainbow Electronics MAX1579 User Manual
Page 6
MAX1578/MAX1579
Complete Bias and White LED Power Supplies
for Small TFT Displays
6
_______________________________________________________________________________________
-5.0
-3.5
-4.0
-4.5
-3.0
-2.5
-2.0
-1.5
-1.0
POS
NEG
-0.5
0
0
40
20
60
80
100
POS AND NEG LOAD REGULATION
MAX1578toc12
LOAD CURRENT (
µA)
VOLTAGE DROOP (%)
-0.6
-0.4
-0.5
-0.2
-0.3
-0.1
0
0
25
MAIN OUTPUT LOAD REGULATION
MAX1578toc11
LOAD CURRENT (mA)
VOLTAGE DROOP (%)
10
5
15
20
PIN
NAME
FUNCTION
1
MAIN
LDO Output and the POS and NEG Charge-Pump Inputs. V
MAIN
is regulated to 5V. Bypass to GND
with a 1µF capacitor. Output is internally discharged with a 1k
Ω resistor when V
ONBIAS
= 0V.
2
CU1
POS Charge-Pump Capacitor Connection 1. Connect a 1µF capacitor between CU1 and PMP.
3
CU2
POS Charge-Pump Capacitor Connection 2. Connect a 1µF capacitor between CU2 and PMPB.
4
CU3
POS Charge-Pump Capacitor Connection 3. Connect a 1µF capacitor between CU3 and GND.
5
POS
Output of Positive (3x) Charge Pump. Bypass POS to GND with a 1µF capacitor. POS is internally
discharged with a 3k
Ω resistor when V
ONBIAS
= 0V.
6
PMP
Charge-Pump Capacitor Connection. Connect a 1µF capacitor between PMP and CU1 and another
1µF capacitor between PMP and CD1.
7
PMPB
Charge-Pump Capacitor Connection. Connect a 1µF capacitor between PMPB and CU2 and another
1µF capacitor between PMPB and CD2. PMPB is 180
° out of phase with PMP.
8
CD1
NEG Charge-Pump Capacitor Connection 1. Connect a 1µF capacitor and a 200
Ω ±5% resistor in
series between CD1 and PMP.
9
CD2
NEG Charge-Pump Capacitor Connection 2. Connect a 1µF capacitor and a 200
Ω ±5% resistor in
series between CD2 and PMPB.
10
NEG
Output of Inverting (-2x) Charge Pump. Bypass NEG to GND with a 1µF capacitor. Output is internally
discharged with a 1.5k
Ω resistor when V
ONBIAS
= 0V.
Pin Description
Typical Operating Characteristics (continued)
(Circuit of Figure 3, V
IN
= 3.6V, I
LED
= 20mA, 4 LEDs, CTRL = IN, T
A
= +25
°C, unless otherwise noted.)