Datasheet

MAX4959/MAX4960
High-Voltage OVP with Battery Switchover
7
Maxim Integrated
only if the backup capacitor on V
DD
is large enough to
maintain power for greater than the 10ms blanking time.
The detection that the adapter is unplugged and
plugged in again is implemented by monitoring the V
IN
signal. The adapter is unplugged when V
IN
drops below
V
IN
= ~0.75V, and it is plugged in when V
IN
becomes
greater than V
IN
= ~0.75V. To ensure the monitoring of
this lower threshold, an external storage capacitor at the
V
DD
pin is necessary. When the input voltage V
IN
drops
below 4V, power for some internal V
IN
monitoring circuit-
ry is supplied by the external capacitor at the V
DD
pin.
This capacitor is supplied by V
IN
through a diode and is
internally limited to 5.5V.
Adapter Not Present (V
IN
< V
UVLO
)
When the input voltage V
IN
drops below 4.4V, P1 is
turned off automatically and P1 does not turn on again
until the adapter is unplugged (V
IN
< ~0.75V) and
plugged in again. When the adapter is not present, P1 is
kept off with the gate-source resistor (which is internal for
the MAX4960 and external for the MAX4959), and the
CB pin controls the battery switchover pFET P2.
MAX4960
+
-
+
-
+
-
+
-
GATE2
CB
GND
UVS
OVS
V
DD
N2
N1
GATE1SOURCE1
N
IN
V
SG
+
-
+
-
LOGIC
DIGITAL
SUPPLY
ANALOG
SUPPLY
BANDGAP
UVLO
OVLO
UVLOINT
POWER
ON
V
DD
UVLO
VREF1 = 2V
VREF2 = 0.7V
POWER-ON
RESET AND
OFF STORAGE
Functional Diagram for the MAX4960
Functional Diagrams (continued)