NCP1800 ON, NCP1800 Datasheet - Page 12

• Manufacturer Part Number: NCP1800
• Description: Single-Cell Lithium Ion Battery Charge Controller
• Manufacturer: ON

Selecting External Components
External Adaptor Power Supply Voltage Selection
the efficiency is lower. Adapter voltage selection must be
done carefully in order to minimize the heat dissipation. In
general, the power supply input voltage should be around
5.0 to 6.0 V. The minimum input voltage should be chosen
to minimize the heat dissipation in the system. Excessively
high input voltages can cause too much heat dissipation and
will complicate the thermal design in applications like
cellular phones. With the overvoltage protection feature of
the NCP1800, input voltages higher than 7.0 V will activate
the overvoltage protection circuit and disconnect the power
supply input to the battery and other circuitry.
NTGS3441 and MBRM130L):
(assuming NTHD4P01FT1):
 5% output voltage adaptor must be used.
V 1% output voltage adaptor can then be used. It is obvious
that if tighter tolerance adaptors are used, heat dissipation
can be minimized by using lower nominal voltage adaptors.
Pass Element Selection
input-output differential voltage, charging current, current
sense resistor and the type of blocking diode used.
criteria:
Drop across pass element =
V IN(min) u Li- ion regulated voltage
V IN(min) u Li- ion regulated voltage,
V IN(min) * Li- ion regulated voltage * V F * I REG
Since the NCP1800 is using a linear, charging algorithm,
For the application shown in Figure 18 (assuming
Therefore, for the application shown in Figure 17
If the output voltage accuracy is 5%, then a typ. 5.2 V
And for a very good regulated adaptor of accuracy 1%, 5.0
The type and size of the pass transistor is determined by
The selected pass element must satisfy the following
u 4.2 V ) (0.12 A)(130mW) ) 0.43
u 4.2 V ) (0.6 A) (100 mW) ) 0.38 V
) (0.12 A)(2.0 W) + 4.89 V ] 4.9 V
V REG ) (0.6 A)(R DS(ON) )
) V F of Schottky Diode ) voltage drop of R SNS
) (0.6 A) (0.4 W) + 4.88 V ] 4.9 V
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R SNS
NCP1800
12
With:
Dropout across pass element =
0.3 W at 0.6 A.
(0.12)(2.0 W) = 0.13 V.
(0.13 V)/(0.12 A) = 1.08 W at 0.12 A.
External Output Capacitor
the capacitor’s minimum ESR. However, a 10 mF tantalum
capacitor or electrolytic capacitor is recommended at the
output to suppress fast ramping spikes at the V
to ensure stability for 1.0 A at full range. The capacitor
should be mounted with the shortest possible lead or track
length to the VSNS and GND pins.
Current Sense Resistor
sense resistor as in the previous formula. Proper de-rating
is advised when selecting the power dissipation rating of the
resistor. If necessary, R
selection of the R
full-char ge current ranges specified in the electrical
characteristics section. Also notice the effect of RISEL on
the accuracy of pre-charge current and end-of-charge
detection as noted in Figures 10 and 12, respectively.
Maximum R
Dropout across pass element = 5.0 V - 4.2 V - 0.43 V -
Therefore, maximum R
Any good quality output filter can be used, independent of
The charging current can be set by the value of the current
5.0 V * 4.2 V * 0.38 V * (0.6 A) (0.4 W) + 0.18 V
V IN(min) + 5.0 V
V IN(min) + 5.0 V
DS(on)
V REG + 4.2 V
V REG + 4.2 V
R SNS + 0.4 W
R SNS + 2.0 W
I REG + 0.6 A
I REG + 0.12 A
SNS
values. Take note of the recommended
should be less than (0.18 V)/(0.6 A) =
ISEL
can also be changed for proper
DS(on)
should be less than
SNS
input and