MAX1677
Compact, High-Efficiency, Dual-Output
Step-Up and LCD Bias DC-DC Converter
4 _______________________________________________________________________________________
Note 1: The MAX1677 operates in bootstrap mode (operates from the output voltage). Once started, it will operate down to 0.7V
input. If V
IN
exceeds the set V
OUT
, V
OUT
will follow one diode drop below V
IN
.
Note 2: C
REF
= 0.22µF for applications where I
REF
> 10µA.
Note 3: In low-power mode (CLK/SEL = GND), the output voltage regulates 1% higher than in low-noise mode (CLK/SEL = OUT or
synchronized).
Note 4: The device is in a startup mode when V
OUT
is below this value.
Note 5: Specifications to -40°C are guaranteed by design and not production tested.
ELECTRICAL CHARACTERISTICS
(V
OUT
= 3.3V, C
REF
= 0.1µF, POUT = OUT, T
A
= -40°C to +85°C, unless otherwise noted. ) (Note 5)
LBO Output Low Voltage
V
LBO(LO)
Sink current = 1mA
LCDPOL = OUT or GND 300 450
0.1 V
µA
Supply Current
Main DC On, LCD Off
Supply Current All On,
Main DC-DC in PFM Mode
I
PFM
No load, current into OUT 60 µA
VFB Regulation Voltage
µALX Leakage Current
Startup to Normal Mode Transition
Voltage (Note 4)
CONDITIONS
V
LOCKOUT
2.1 2.4 V
I
LX(LEAK)
5
Output Voltage V
OUT
FB = GND, 0 ≤ I
LX
≤ 350mA,
CLK/SEL = OUT (Note 3)
3.17 3.46 V
V
FB(REG)
Adjustable mode, CLK/SEL = OUT (Note 3) 1.22 1.28
µA
Supply Current All On,
Main DC-DC in PWM Mode
Supply Current in Shutdown 5 µA
I
PWM
No load, current into OUT 300
I
LCDOFF
No load, current into OUT 40
LX Current Limit
I
LX(PWM)
N-channel PWM mode 550 900
mA
UNITSMIN MAXSYMBOLPARAMETER
I
LX(PFM)
N-channel PFM mode 250 500
Internal Oscillator f CLK/SEL = OUT 240 360 kHz
External Clock Frequency Range 200 400 kHz
ON Input Threshold
V
ON(LOW)
1.1V < V
OUT
< 5.5V
0.2V
OUT
V
V
ON(HIGH)
0.8V
OUT
LCDON, LCDPOL, CLK/SEL
Input Threshold
V
IL
0.2V
OUT
V
V
IH
0.8V
OUT
LBI Falling Threshold V
LBI(TH)
599 629 mV
LCD BIAS DC-DC
LCDLX Switch Current Limit
LCDPOL connected to OUT or GND
through 50kΩ
150 300
mA
LCDFB Set Point
Positive LCD, LCDPOL = OUT 1.22 1.28 V
-20 +20Negative LCD, LCDPOL = GND mV
GENERAL
MAIN
LCD BIAS DC-DC
LOGIC
