LTC2920-2CMS8#TR Linear Technology, LTC2920-2CMS8#TR Datasheet - Page 14

• Manufacturer Part Number: LTC2920-2CMS8#TR
• Description: IC SNGL/DUAL PWR SUP CTRLR 8MSOP
• Manufacturer: Linear Technology

Specifications of LTC2920-2CMS8#TR

• Applications: Single/Dual Power Supply Controller
• Voltage - Supply: 2.3 V ~ 6 V
• Current - Supply: 230µA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Voltage - Input: -

LTC2920-1/LTC2920-2
APPLICATIO S I FOR ATIO
voltage. The value of the R
lated by:
With C
additional filtering is necessary, the value of C
increased. In this example, if C
to 1μF, the pole would now be at 287Hz.
Controlling I
Designers of power supply voltage margining circuits
often need to ensure that power supply voltages do not
overshoot or undershoot (the desired margining voltage)
when the margining current is enabled or disabled. The
LTC2920 I
pin(s) is reasonably well behaved (see the Typical Perfor-
mance Characteristics curves). The differences in speed
between the various curves is caused by the relative
impedance differences within the LTC2920.
If slower turn on and turn off times are desired, a resistor-
capacitor network can be used at the I
14
R
BYP
BYP
0.1μF
= V
C
BYP
R
SET
MARGIN
= 0.1μF, this will provide a pole at 2870Hz. If
RB
MARGIN
Figure 18. Diode Connected to V
/I
Figure 19. V
CCMAX
R
LTC2920
S
GND
V
CC
current sourced or sinked at the I
I
U
M
POWER SUPPLY 1
POWER SUPPLY 2
Turn On and Turn Off Times
FB
FB
I
I
M2
M1
I
LTC2920-2
= 0.5V/1.4mA = 360Ω
MARGIN
100μA
CC
U
BYP
OUT
OUT
=
V
360Ω
CC
R
BYP
Power Filtering
BYP
SCHOTTKY
R
R
resistor can then be calcu-
F
G
BAT54C
DIODE
is increased from 0.1μF
–
2920-1/2 F18
W
V
POWER
M
pin(s). Referring
+
+
–
V
CC
PSOUT
V
REF
2920-1/2 F19
= 1.2V
= 3.3V
BYP
U
can be
M
to Figure 20, Slowing Down V
a resistor (R
described in previous applications sections. To choose
R
must be known. Refer to the power supply manufacturer’s
data sheet for this voltage. The voltage at the I
be within specified limits of the LTC2920, including the
voltage drop across R
supply feedback pin voltage is 1.21V, I
and V
the voltage at the I
(V
value for the voltage drop across R
R
Assuming the desired RC time constant is 1ms, C
calculated by:
Note: When C
zero are added to the power supply feedback loop. It is
beyond the scope of this data sheet to predict the behavior
of all power supplies but, in general, as long as the smaller
of the two feedback resistors is no larger than 2 • R
effect on the power supply stability should be minimal. The
larger R
less effect it will have.
Thermal Shutdown
This IC includes overtemperature protection that is in-
tended to protect the device during momentary overload
conditions. Junction temperature will exceed 125°C when
overtemperature protection is active. Continuous opera-
tion above the specified maximum operating junction
temperature may result in device degradation or failure.
S
S
CC
, the voltage at the feedback pin of the power supply
R
C
is then:
S
S
– 1) or 2.3V (in the low current range). A reasonable
CC
= T
= V
S
is 3.3V. To maintain LTC2920 current accuracy,
RC
RS
is with respect to the two feedback resistors, the
/R
/I
S
) have been added to the power supply model
MARGIN
LTC2920
Figure 20. Slowing Down V
S
S
3.3V
GND
V
CC
and R
= 1ms/5k = 0.2μF
I
M
I
M
MARGIN
= 0.5V/100μA = 5k
S
S
C
0.2μF
pin must be between 0.58V and
S
R
5k
. In the example below, the power
are used, an additional pole and a
S
5k
1.5k
MARGIN
–
S
, a capacitor (C
is 0.5V. The value of
MARGIN
+
+
–
2920-1/2 F20
V
1.21V
MARGIN
REF
M
is 100μA
pin must
S
292012fa
S
) and
, the
S
is