Rainbow Electronics MAX1844 User Manual
Page 3
MAX1844
High-Speed Step-Down Controller with
Accurate Current Limit for Notebook Computers
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V+ = 15V, V
CC
= V
DD
= 5V, SKIP = GND,
T
A
= 0
°
C to +85
°
C
, unless otherwise noted. Typical values are at
T
A
= +25
°
C.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
REF Sink Current
REF in regulation
10
µA
REF Fault Lockout Voltage
Falling edge, hysteresis = 40mV
1.6
V
Overvoltage Trip Threshold
(Fixed-Threshold Mode)
With respect to error comparator threshold, no load
OVP = GND, rising edge, hysteresis = 1%
12
14.5
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,
rising edge, hysteresis = 1%
-3.5
+3.5
%
OVP Input Leakage Current
1V < V
OVP
< 1.8V
-100
0
+100
nA
Overvoltage Fault
Propagation Delay
FB forced 2% above trip threshold
1.5
µs
Output Undervoltage Protection
Trip Threshold (Fixed-Threshold
Mode)
With respect to error comparator threshold, UVP = V
CC
65
70
75
%
External feedback, measured at FB with respect to
V
UVP
,
0.4V < V
UVP
< 1V
-40
+40
mV
Output Undervoltage Protection
Trip Threshold (Adjustable-
Threshold Mode)
Internal feedback, measured at OUT with respect to the
nominal OUT regulation voltage, 0.4V < V
UVP
< 1V
-5
+5
%
UVP Input Leakage Current
0.4V < V
UVP
< 1V
-100
<1
+100
nA
Output Undervoltage Protection
Blanking Time
From rising edge of SHDN
10
30
ms
PGOOD Trip Threshold (Lower)
With respect to error comparator threshold, no load
-12.5
-10
-8
%
PGOOD Trip Threshold (Upper)
With respect to error comparator threshold, no load
8
10
12.5
%
PGOOD Propagation Delay
FB forced 2% beyond PGOOD trip threshold, falling
10
µs
PGOOD Output Low Voltage
I
SINK
= 1mA
0.4
V
PGOOD Leakage Current
High state, forced to 5.5V
1
µA
ILIM Adjustment Range
0.25
3
V
Current-Limit Threshold (Fixed)
GND - V
CS
, ILIM = V
CC
90
100
110
mV
V
ILIM
= 0.5V
40
50
60
Current-Limit Threshold
(Adjustable)
GND - V
CS
V
ILIM
= 2V
170
200
230
mV
Current-Limit Threshold
(Negative Direction)
GND - V
CS
, SKIP = V
CC
, ILIM = V
CC
,T
A
= +25°C
-140
-117
-95
mV
Current-Limit Threshold
(Zero Crossing)
GND - V
CS,
SKIP = GND
3
mV
Thermal Shutdown Threshold
Hysteresis = 10°C
150
°C
V
CC
Undervoltage
Lockout Threshold
Rising edge, hysteresis = 20mV,
PWM disabled below this level
4.1
4.4
V