Rainbow Electronics MAX1844 - Manual (Page 5)

MAX1844
High-Speed Step-Down Controller with
Accurate Current Limit for Notebook Computers
_______________________________________________________________________________________ 5
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Off-Time (Note 2) 500 ns
Quiescent Supply Current (V CC ) FB forced above the regulation point 800 µA
Quiescent Supply Current (V DD ) FB forced above the regulation point 5 µA
Quiescent Supply Current (V+) Measured at V+ 40 µA
Shutdown Supply Current (V CC ) SHDN = GND 5 µA
Shutdown Supply Current (V DD ) SHDN = GND 5 µA
Shutdown Supply Current (V+) SHDN = GND, V+ = 28V, V
CC = V DD = 0 or 5V 5 µA
Reference Voltage V CC = 4.5V to 5.5V, no external REF load 1.98 2.02 V
Overvoltage Trip Threshold
(Fixed-Threshold Mode)
With respect to error comparator threshold, no load
OVP = GND, rising edge, hysteresis = 1%
12 17 %
External feedback, measured at FB with respect to
V
OVP
, 1V < V
OVP
1.8V, rising edge, hysteresis = 1%
-30 +30 mV
Overvoltage Comparator Offset
(Adjustable-Threshold Mode)
Internal feedback, measured at OUT with respect to the
nominal OUT regulation voltage, 1V < V
OVP < 1.8V
-3.5 +3.5 %
PGOOD Trip Threshold (Lower)
With respect to error comparator threshold, no load
OUT falling edge, hysteresis = 1%
-12.5 -7.5 %
PGOOD Trip Threshold (Upper)
With respect to error comparator threshold, no load
OUT rising edge, hysteresis = 1%
7.5 12.5 %
PGOOD Output Low Voltage I SINK = 1mA 0.4 V
PGOOD Leakage Current High state, forced to 5.5V 1 µA
Current-Limit Threshold (Fixed) GND - V CS , ILIM = V CC 85 115 mV
GND - V CS , V ILIM = 0.5V 35 65 Current-Limit Threshold
(Adjustable)
GND - V CS , V ILIM = 2V 160 240
mV
V CC Undervoltage
Lockout Threshold
Rising edge, hysteresis = 20mV,
PWM disabled below this level
4.1 4.4 V
Logic Input High Voltage LATCH, SHDN, SKIP 2.4 V
Logic Input Low Voltage LATCH, SHDN, SKIP 0.8 V
Logic Input Current LATCH, SHDN, SKIP -1 1 µA
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V+ = 15V, V
CC
= V
DD
= 5V, SKIP = GND, T
A
= -40 ° C to +85 ° C , unless otherwise noted.) (Note 3)
Note 1: When the inductor is in continuous conduction, the output voltage will have a DC regulation level higher than the error com-
parator threshold by 50% of the ripple. In discontinuous conduction (SKIP = GND, light load), the output voltage will have a
DC regulation level higher than the trip level by approximately 1.5% due to slope compensation.
Note 2: On-time and off-time specifications are measured from 50% point to 50% point at the DH pin with LX = GND, V BST = 5V,
and a 250pF capacitor connected from DH to LX. Actual in-circuit times may differ due to MOSFET switching speeds.
Note 3: Specifications to -40°C are guaranteed by design, not production tested.
Note 4: Production testing limitations due to package handling require relaxed maximum on-resistance specifications for the QFN
package. The MAX1844EEP and MAX1844EGP contain the same die and the QFN package imposes no additional resis-
tance in-circuit.