Rainbow Electronics MAX1885 - Manual (Page 3)

MAX1778/MAX1880–MAX1885
Quad-Output TFT LCD DC-DC
Converters with Buffer
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(V IN = +3.0V, SHDN = IN, V SUPP = V SUPN = V SUPB = V SUPL = 10V, LDOOUT = FBL, BUF- = BUFOUT, BUF+ = FLTSET = TGND =
PGND = GND, C REF = 0.22µF, C BUF = 1µF, T A = 0°C to +85°C. Typical values are at T A = +25°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAIN STEP-UP CONVERTER
Main Output Voltage Range V MAIN V IN 13 V
Integrator enabled, C INTG = 1000pF 1.234 1.247 1.260
FB Regulation Voltage V FB
Integrator disabled (INTG = REF) 1.220 1.280
V
FB Input Bias Current I FB V FB = 1.25V, INTG = GND -50 +50 nA
MAX1778/MAX1880/MAX1883 0.85 1 1.15 MHz
Operating Frequency f
OSC
MAX1881/MAX1882/MAX1884/MAX1885 425 500 575 kHz
Oscillator Maximum Duty
Cycle
80 85 91 %
Integrator enabled,
C
INTG = 1000pF
0.01
Load Regulation
I LX = 0 to 200mA,
V MAIN = 10V
Integrator disabled
(INTG = REF)
0.2
%
Line Regulation 0.1 %/V
Integrator Transconductance 317 µs
LX Switch On-Resistance R LX(ON) I LX = 100mA 0.35 0.7 Ω
LX Leakage Current I LX V LX = 13V 0.01 20 µA
Phase I = soft-start (1024/f OSC ) 0.275 0.38 0.5
Phase II = soft-start (1024/f OSC ) 0.75
Phase III = soft-start (1024/f OSC ) 1.12
LX Current Limit I LIM
Phase IV = fully-on (after 3072/f OSC ) 1.15 1.5 1.85
A
Maximum RMS LX Current 1 A
Soft-Start Period t SS Power-up to the end of Phase III 3072 / f OSC s
Falling edge, FLTSET = GND 1.07 1.1 1.14
FB Fault Trip Level
Falling edge, FLTSET = 1V 0.955 0.99 1.025
V
POSITIVE CHARGE PUMP (MAX1778/MAX1880/MAX1881/MAX1882 ONLY)
SUPP Input Supply Range V SUPP 2.7 13 V
Operating Frequency f CHP 0.5 x f OSC
Hz
FBP Regulation Voltage V FBP 1.2 1.25 1.3 V
FBP Input Bias Current I FBP V FBP = 1.5V -50 +50 nA
DRVP PCH On-Resistance R PCH(ON) 5 10
Ω
V FBP = 1.2V 2 4
Ω
DRVP NCH On-Resistance R NCH(ON)
V FBP = 1.3V 20 k Ω
Maximum RMS DRVP Current 0.1 A
FBP Power-Ready Trip Level Rising edge 1.09 1.125 1.16 V
Falling edge, FLTSET = GND 1.08 1.11 1.16
FBP Fault Trip Level
Falling edge, FLTSET = 1V 0.955 0.99 1.025
V