Datasheet

Analog Integrated Circuit Device Data
12 Freescale Semiconductor
34671
FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
Figure 20. 34671 Functional Internal Block Diagram
INTEGRATED SUPPLY
INTERNAL SUPPLY AND REFERENCE
This block steps down the high input voltage to a lower
voltage to power all the internal blocks. In addition, this block
generates the reference voltage for the charge control block.
SENSING AND CONTROL
VIN MONITOR
The input voltage monitor block monitors the input voltage
for two thresholds, power-on-reset (POR) and over-voltage
protection (OVP). If the input is lower than the POR or higher
than the OVP threshold, this block outputs a logic signal to
disable the charger.
CHARGE CONTROL
The charge-control block controls the gate voltage of the
power MOSFET to regulate the charge current, the battery
voltage, or the die temperature. It can also completely turn off
the power MOSFET to stop the current flow between the
input and the battery. Also, monitoring of the charge current
and the charger output voltage determines the trickle-charge
mode and the recharge cycle.
CURRENT SETTING AND MONITOR
This block programs the charge current in the constant-
current mode and monitors the actual charge current during
the whole charge cycle.
EOC (END OF CHARGE)
The EOC block monitors the charge current and the battery
voltage for the EOC conditions. Once the EOC conditions are
reached, this block outputs a logic signal to indicate the end
of the charge.
VIN-BAT COMPARATOR
The VIN-BAT comparator monitors the voltage difference
between the input voltage and the battery voltage. The input
voltage has to be higher than the battery voltage for the
charger to be enabled. If the input voltage falls below the
battery voltage, this block outputs a signal to disable the
charger to prevent the leakage current from the battery to the
input.
DIE TEMPERATURE FEEDBACK
The die temperature feedback block monitors the die
temperature. Once the die temperature reaches the
threshold temperature, the charge control block can reduce
the charge current to prevent further die temperature rise.
MC34671 - Functional Block Diagram
Integrated Supply
Sensin
g
& Contro
l
M
OS
FET
P
ower M
OS
FET
Log
ic
Integrated Supply
Internal Supply & Reference
Sensin
g
& Control
L
o
g
i
c
Di
e
T
emperature
F
ee
db
ac
k
Current Setting
Cu
rr
e
nt M
o
nit
o
r
S
t
a
t
us
In
d
i
ca
ti
on
V
IN - BAT
C
ompare
V
IN
M
on
i
to
r
C
harge Contro
l
Logic Contro
l
E
nd of Charge