max2003cse Maxim Integrated Products, Inc., max2003cse Datasheet - Page 9

• Manufacturer Part Number: max2003cse
• Description: Nicd/nimh Battery Fast-charge Controllers Integrated Products
• Manufacturer: Maxim Integrated Products, Inc.

Table 2. Device Status on Power-Up if
Battery is Already Present
Before a battery is inserted, the BAT pin is pulled high-
er than the maximum cell voltage (MCV) by the resistor
(R
When the battery is inserted, the voltage per cell at BAT
falls from the default voltage to the battery voltage.
Fast-charge is initiated on a falling edge when the BAT
voltage crosses the voltage on MCV.
There may be some cases where a battery is connect-
ed before power is applied to the MAX2003/
MAX2003A. When power is applied, the device goes
into reset mode for approximately 1.5sec and then
samples the CCMD and DCMD pins. Its charge status
is determined by the voltage at both the CCMD and
DCMD pins. Table 2 summarizes the various conditions
the MAX2003/MAX2003A might see on power-up.
Table 2 shows that the MAX2003/MAX2003A can be
set-up for fast-charge on power-up by making sure
CCMD and DCMD are at the same potential. If fast-
charge on power-up is not desired, make sure CCMD
and DCMD are at different logic levels during power-
up, and use a digital signal to control fast-charge (see
Digital Control section).
The CCMD pin can be used to initiate fast-charge. This is
useful when neither the power supply nor the battery can
be removed from the charger. The CCMD signal needed
to initiate fast-charge depends on the potential at DCMD.
If DCMD is low, a rising edge on CCMD initiates fast-
charge. If DCMD is high, a falling edge on CCMD pro-
vides the fast-charge signal. Table 3 summarizes the
conditions used to start fast-charge.
CCMD
High
High
TR
Low
Low
) and the divider network (R
Applying Power to the MAX2003/MAX2003A
DCMD
High
High
Low
Low
_______________________________________________________________________________________
• Fast-charge is initiated on power-up.
• The device does not enter fast-charge
• Fast-charge is initiated by the falling
• The device does not enter fast-charge
• Fast-charge is initiated by the rising
• Fast-charge is initiated on power-up.
MAX2003/MAX2003A Status when
immediately.
edge of a pulse on CCMD.
immediately.
edge of a pulse on CCMD.
Power is Applied
(battery already present)
Battery Replacement
B1
/R
B2
Digital Control
) (Figure 1).
Fast-Charge Controllers
Table 3. Digital Control of Fast-Charge
(V
The discharge-before-charge function is optional and
can be used to condition old batteries. It is especially
useful in NiCd batteries, since it alleviates the voltage
depression problems associated with partially dis-
charged NiCd cells. The discharge-before-charge
function is initiated by a rising edge into DCMD.
When the digital signal is applied, the DIS pin will be
pulled high, turning on the attached circuit and dis-
charging its battery. The discharge process continues
until the single cell voltage drops below 0.2V
the discharge phase, the CHG pin will be low (LED on)
for 1.375sec and high (LED off) for 0.125sec.
The MAX2003/MAX2003A does not control the current
during discharge-before-charge. If the discharge rate
is too great, the battery could overheat and be dam-
aged. The battery manufacturer will be able to specify
a safe discharge rate, but a rate of C or slower is typi-
cally acceptable. It is also important to choose compo-
nents (Q2, R
discharge rate. Since the gate-source drive for Q2 can
be as low as 4.5V, use a logic-level MOSFET.
The fast-charge current can be generated using two
categories of circuits:
The standard application circuit of Figure 1 uses an
inductor and a switched mode of operation to supply
the current. The charge current is determined by the
sense resistor placed between the negative terminal of
the battery (SNS) and ground (V
The SNS pin is the input to a comparator with hystere-
sis. If the voltage at SNS drops below 0.044V
MOD pin is turned on. If the SNS voltage is above
0.050V
CCMD
CC
• Circuits with a sense resistor (R
• Circuits without sense resistor (SNS tied to V
CC
and battery present)
, MOD is turned off. In the switched mode of
NiCd/NiMH Battery
Discharge-Before-Charge (optional)
DCMD
High
Low
DIS
) that are rated for that particular
• Fast-charge is initiated by a rising
• Fast-charge is initiated by a falling
CCMD Status to Initiate Fast-Charge
edge on CCMD.
edge on CCMD.
Circuits with SNS Resistor
Fast-Charge Current
SS
).
SNS
)
CC
. During
CC
, the
SS
)
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