Datasheet

LTC4064
14
sn4064 4064fs
PROG pin. With no additional capacitance on the PROG
pin, stability is acceptable with program resistor values as
high as 50k. However, additional capacitance on this node
reduces the maximum allowed program resistor. The pole
frequency at the PROG pin should be kept above 500kHz.
Therefore, if the PROG pin is loaded with a capacitance, C,
the following equation should be used to calculate the
maximum resistance value for R
PROG
:
R
PROG
< 1/(6.283 • 5 × 10
5
• C)
5
7
R
PROG
C
FILTER
CHARGE
CURRENT
MONITOR
CIRCUITRY
10k
LTC4064
4064 F05
GND
PROG
Figure 5. Isolating Capacitive Load on PROG Pin and Filtering
APPLICATIO S I FOR ATIO
WUUU
Average, rather than instantaneous, battery current may
be of interest to the user. For example, if a switching power
supply operating in low-current mode is connected in
parallel with the battery the average current being pulled
out of the BAT pin is typically of more interest than the
instantaneous current pulses. In such a case, a simple RC
filter can be used on the PROG pin to measure the average
battery current as shown in Figure 5. A 10k resistor is
added between the PROG pin and the filter capacitor and
monitoring circuit to ensure stability.