User Manual

MAX1578/MAX1579
Complete Bias and White LED Power Supplies
for Small TFT Displays
_______________________________________________________________________________________ 3
PARAMETER CONDITIONS
MIN TYP MAX
UNITS
NEG Output Voltage I
LOAD
= 0 to -100µA
-10.2 -9.8 -9.3
V
N E G D i schar g e S w i tch Resi stance
V
ONBIAS
= 0V 1.5 3 kΩ
LOGIC INPUT (ONBIAS)
Logic Input Low Voltage
0.72
V
Logic Input High Voltage 1.6 V
T
A
= +25°C
0.01
1
Input Current
T
A
= +85°C 1
µA
LED BACKLIGHTING
Efficiency LOAD = 6 LEDs in series at 20mA 84 %
OUT Voltage Range (Note 2)
(V
IN
-
V
D1
)
32 V
Overvoltage-Lockout (OVLO)
Threshold
V
OUT
rising, 2V hysteresis 32 34 36 V
V
OUT
= 32V, V
CTRL
> 0.24V 10 20 32
T
A
= +25°C 0.01
1
OUT Input Bias Current
V
OUT
= V
IN
, V
CTRL
= 0
T
A
= +85°C
0.1
µA
ERROR AMPLIFIER
T
A
= +25°C
0.295 0.300 0.305
CTRL to CS Regulation
V
CTRL
= 1.5V, V
IN
= 2.7V to
5.5V
T
A
= -40°C to +85°C
0.292 0.300 0.308
V
T
A
= +25°C
0.01
1
CS Input Bias Current V
CS
= V
CTRL
/ 5
T
A
= +85°C
0.03
µA
MAX1578
250 500 780
T
A
= +25°C 250 500 780
CTRL Input Resistance V
CTRL
< 1.0V
MAX1579
T
A
= +85°C 185
kΩ
CTRL Dual Mode™ Threshold 5mV hysteresis
100 170 240
mV
CTRL Shutdown Delay (Note 3) 6.5 8.2
10.5
ms
CS to COMP Transconductance V
COMP
= 1.0V 32 60 90 µS
CS Regulation Derating Function
Start Temperature
V
CTRL
= 3V, MAX1579 only
+42
°C
CS Regulation Derating Function
Slope
V
CTRL
= 3V, T
A
= +65°C, MAX1579 only -6
mV/°C
MAX1578, V
CTRL
= 3V
310 327 345
CS Maximum Brightness Clamp
Voltage
MAX1579, V
CTRL
= 3V, T
A
= +25°C
322 340 358
mV
MAX1578
1.635
CS Maximum Brightness Voltage
at CTRL
MAX1579
1.70
V
OSCILLATOR
Operating Frequency f
BOOST
0.8 1.0 1.2 MHz
PWM mode 12
Minimum Duty Cycle
Pulse skipping 0
%
Maximum Duty Cycle CTRL = IN, CS = GND 92 95 %
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 3, V
IN
= 3V, CTRL = ONBIAS = IN, T
A
= -40°C to +85°C, typical values are at T
A
= +25°C, unless otherwise noted. Note 1)
Dual Mode is a trademark of Maxim Integrated Products, Inc.