ISL6292C 查看數據表（PDF） - Renesas Electronics
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ISL6292C Datasheet PDF : 11 Pages
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ISL6292C
Stability With Large Ceramic Output Capacitors
The ISL6292C partially relies on the ESR (equivalent series
resistance) of the output capacitor for the loop stability.
When the system has a large ceramic capacitor or a number
of ceramic capacitors in parallel, the ESR value can be too
low for a stable operation. A low-value resistor should be
inserted between the sensed feedback (VSEN pin) and the
external large-value ceramic capacitor to improve the
stability, as shown in Figure 9.
In applications that have a sense resistor between the VBAT
pin and the VSEN pin, such as the R1 shown in Figure 10,
two small resistors can be used to create an equivalent low
value resistor between the VSEN pin and the large capacitor,
to avoid another more expensive low-value sense resistor.
R2 and R3 in Figure 10 show how the two resistors are
connected. The equivalent low-value resistance is,
Req= R-----2--R---+--3--R-----3- R1
(EQ. 7)
The value of (R2 + R3) should be significantly larger than
that of the sense resistor R1 to minimize the accuracy of the
current sensing. The parallel value of R2 and R3 should be
significantly smaller than 72k (internal resistive divider
value for setting the charger output voltage) to minimize the
impact on the output voltage. Figure 10 shows two 20
resistor. The sum is 40, much higher than the 150m R1.
The parallel value is 10, negligible compared to the 72k
resistive divider. Such a selection is a good trade-off to result
in 75m equivalent low-value resistance between the VSEN
pin and the large capacitor.
To INPUT
ISL6292C
VIN
VBAT
R1 75m To Battery
C1
10F
Ceramic
VSEN
GND
C2
Large
Ceramic
Capacitor
FIGURE 9. INSERTING R1 TO IMPROVE THE STABILITY OF
APPLICATIONS WITH LARGE CERAMIC
CAPACITOR IS USED AT THE OUTPUT
To INPUT
C1
10F
Ceramic
ISL6292C
VIN
VBAT
R1 150m
To Battery
VSEN
GND
R2 20
R3 20
C2
Large
Ceramic
Capacitor
FIGURE 10. THE CIRCUIT TO GENERATE THE EQUIVALENT
LOW-VALUE RESISTOR
Working with Current-Limited Adapter
The ISL6292C can work with a current-limited adapter to
significantly reduce the thermal dissipation during charging.
Refer to the ISL6292 data sheet, which can be found at
http://www.intersil.com, for more details.
Board Layout Recommendations
The ISL6292C internal thermal foldback function limits the
charge current when the internal temperature reaches
approximately 100°C. In order to maximize the current
capability, it is very important that the exposed pad under the
package is properly soldered to the board and is connected
to other layers through thermal vias. More thermal vias and
more copper attached to the exposed pad usually result in
better thermal performance. On the other hand, the number
of vias is limited by the size of the pad. The 3x3 DFN
package allows 8 vias be placed in two rows. Since the pins
on the 3x3 DFN package are on only two sides, as much top
layer copper as possible should be connected to the
exposed pad to minimize the thermal impedance. Refer to
the ISL6292 evaluation boards for layout examples.
© Copyright Intersil Americas LLC 2004-2005. All Rights Reserved.
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For additional products, see www.intersil.com/en/products.html
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in the quality certifications found at www.intersil.com/en/support/qualandreliability.html
Intersil products are sold by description only. Intersil may modify the circuit design and/or specifications of products at any time without notice, provided that such
modification does not, in Intersil's sole judgment, affect the form, fit or function of the product. Accordingly, the reader is cautioned to verify that datasheets are
current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its
subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or
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For information regarding Intersil Corporation and its products, see www.intersil.com
FN9133 Rev.2.00
July 22, 2005
Page 10 of 11
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