LTC1960CG#TR Linear Technology, LTC1960CG#TR Datasheet - Page 22

• Manufacturer Part Number: LTC1960CG#TR
• Description: IC BATT CHRGR/SELECTR DUAL36SSOP
• Manufacturer: Linear Technology
• Type: Battery Chargerr

Specifications of LTC1960CG#TR

• Function: Charge Management
• Voltage - Supply: 6 V ~ 28 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 36-SSOP (0.200", 5.30mm Width)
• Operating Supply Voltage (min): 6V
• Operating Supply Voltage (max): 28V
• Operating Temp Range: 0C to 70C
• Package Type: SSOP
• Mounting: Surface Mount
• Pin Count: 36
• Operating Temperature Classification: Commercial
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: LTC1960CGTR

V
Capacitor C7 is used to filter the delta-sigma modulation
frequency components to a level which is essentially DC.
Acceptable voltage ripple at I
the period of the delta-sigma switch closure, T
10µs and the internal IDAC resistor, R
ripple voltage can be approximated by:
Then the equation to extract C7 is:
In order to prevent overshoot during start-up transients,
the time constant associated with C7 must be shorter than
the time constant of C5 at the I
to improve ripple rejection, then C5 should be increased
proportionally and charger response time to average cur-
rent variation will degrade.
Capacitor C
sigma modulation frequency components to a level which
is essentially DC. C
C
the pole associated with C
at V
sigma switch closure, T
VDAC resistor, R
approximated by:
Then the equation to extract C
C
present at the charger output. Therefore C
C
LTC1960
APPLICATIONS INFORMATION
22
SET
B1
B2
B2
C7 =
C
∆V
∆V
SET
should be 10× to 20× C
= 0.1µF are good starting values. In order to prevent
is used to provide a zero in the response to cancel
B1
/I
SET
ISET
= 0.8/0.01/18.77k(10µs) @ 0.043µF
VSET
|| C
is about 10mV
∆V
Capacitors
V
B2
=
REF
B1
ISET
=
=
V
R
R
and C
REF
R
SET
• T
VSET
VSET
• R
V
VSET
V
∆ ∑
REF
• T
REF
B2
SET
B2
• C7
, is 7.2kΩ, the ripple voltage can be
(
∆ ∑
C
is the primary filter capacitor and
P-P
∆V
are used to filter the VDAC delta-
• T
∆∑
• T
B1
VSET
. Since the period of the delta-
∆ ∑
, is about 11µs and the internal
∆ ∑
|| C
B2
B1
SET
. Acceptable voltage ripple
B2
B1
to divide the ripple voltage
TH
is about 10mV
)
|| C
pin. If C7 is increased
B2
SET
is:
B1
, is 18.77k, the
= 0.01µF and
∆∑
P-P
, is about
. Since
overshoot during start-up transients the time constant as-
sociated with C
of C5 at the I
rejection, then C5 should be increased proportionally and
charger response time to voltage variation will degrade.
Input and Output Capacitors
In the 4A Lithium Battery Charger (Typical Application
section), the input capacitor (C
input switching ripple current in the converter, so it must
have adequate ripple current rating. Worst-case RMS ripple
current will be equal to one-half of output charging current.
Actual capacitance value is not critical. Solid tantalum,
low ESR capacitors have a high ripple current rating in a
relatively small surface mount package, but caution must
be used when tantalum capacitors are used for input or
output bypass. High input surge currents can be created
when the adapter is hot-plugged to the charger or when a
battery is connected to the charger. Solid tantalum capaci-
tors have a known failure mechanism when subjected to
very high turn-on surge currents. Only Kemet T495 series
of “surge robust” low ESR tantalums are rated for high
surge conditions such as battery to ground.
The relatively high ESR of an aluminum electrolytic for
C15, located at the AC adapter input terminal, is helpful
in reducing ringing during the hot-plug event.
Highest possible voltage rating on the capacitor will
minimize problems. Consult with the manufacturer before
use. Alternatives include new high capacity ceramic (at
least 20µF) from Tokin, United Chemi-Con/Marcon, et al.
Other alternative capacitors include OSCON capacitors
from Sanyo.
The output capacitor (C
output switching current ripple. The general formula for
capacitor current is:
For example:
V
I
RMS
DCIN
I
RMS
= 0.41A.
= 19V, V
=
0.29(V
TH
BAT
B2
pin. If C
must be shorter than the time constant
BAT
= 12.6V, L1 = 10µH, and f = 300kHz,
(L1)(f)
) 1−

 
B2
OUT
is increased to improve ripple
) is also assumed to absorb
V
V
DCIN
IN
BAT
) is assumed to absorb all

 
1960fb