Datasheet

MAX1927/MAX1928
Low-Output-Voltage, 800mA, PWM Step-Down
DC-DC Converters
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ELECTRICAL CHARACTERISTICS (continued)
(V
BATT
= 3.6V, SHDN = BATT, C
REF
= 0.1µF, T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER CONDITIONS
MIN TYP MAX
UNITS
N-Channel Synchronous Rectifier Turn-Off
Threshold
20 mA
LX Leakage Current V
BATT
= 5.5V, LX = GND or BATT -20 0.1
+20
µA
Maximum Duty Cycle
100
%
PWM = GND 0
Minimum Duty Cycle
PWM = BATT 15
%
Internal Oscillator Frequency
0.85
1
1.15
MHz
Thermal Shutdown Threshold 15°C hysteresis
160
D eg r ees
POK COMPARATOR
BATT Operating Voltage Range I
POK
= 0.1 mA 1 5.5 V
Output Low Voltage V
FB
= 0.5V, I
POK
= 1mA
0.01
0.1 V
Output High Leakage Current V
POK
= 5.5V 1 µA
MAX1927R
0.650 0.675 0.700
MAX1928-15
1.305 1.350 1.395
MAX1928-18
1.566 1.620 1.674
POK Threshold
MAX1928-25
2.175 2.250 2.325
V
Output Valid to POK Release Delay
POK transitions to high impedance 20ms
after V
FB
> V
POK
15 20 25 ms
LOGIC INPUTS (SHDN, PWM)
Logic Input High 2.6V < V
BATT
< 5.5 V 1.6 V
Logic Input Low 2.6V < V
BATT
< 5.5 V 0.6 V
Logic Input Current V
BATT
= 5.5V 0.1 1 µA
ELECTRICAL CHARACTERISTICS
(V
BATT
= 3.6V, SHDN = BATT, C
REF
= 0.1µF, T
A
= -40°C to +85°C, unless otherwise noted.)
PARAMETER CONDITIONS
MIN MAX
UNITS
BATT Input Voltage 2.6 5.5 V
Undervoltage Lockout Threshold V
BATT
rising or falling (35mV hysteresis)
2.15
2.55
V
Quiescent Current No load, pulse skipping, PWM = GND 240 µA
Quiescent Current in Dropout 340 µA
Shutdown Supply Current SHDN = GND 10 µA
REFERENCE AND ERROR AMP
MAX1927R
0.732 0.768
MAX1928-15
1.47 1.53
MAX1928-18
1.764 1.836
FB Voltage Accuracy
MAX1928-25
2.45 2.55
V
FB Input Current MAX1928 5 15 µA