SC2440TETRT Semtech, SC2440TETRT Datasheet - Page 17

• Manufacturer Part Number: SC2440TETRT
• Description: IC SW REG DUAL 2.5MHZ 16-TSSOP
• Manufacturer: Semtech
• Type: Step-Down (Buck)r

Specifications of SC2440TETRT

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 2
• Current - Output: 2A
• Frequency - Switching: 1.4MHz
• Voltage - Input: 2.8 ~ 20 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP Exposed Pad, 16-eTSSOP, 16-HTSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Power - Output: -
• Other names: SC2440TETR

Overload / Short-Circuit Protection
Each current limit comparator in the SC2440 limits the
peak inductor current to 2.6A. The regulator output
voltage will fall if the load is increased above the current
limit. If overload is detected (the output voltage falls
below 74% of the set voltage), then the regulator will be
shut off. An internal 0.8µA current sink starts to
discharge the soft-start capacitor. As the soft-start
capacitor is discharged below 1V, the discharge current
source turns off and the soft-start capacitor is recharged
with a 1.8µA current source. The regulator undergoes
soft-start. During soft-start (1V < V
shutdown latch in Figure 3 cannot be set. When V
exceeds 2V, the set input of the overload latch is no
longer blanked. If V
regulator will undergo shutdown and restart. The soft-
start process should allow the output voltage to reach
74% of its final value before C
Figures 10(a) and 10(b) show the timing diagrams of
successful and failed start-up waveforms respectively.
The soft-start interval should also be made sufficiently
long so that the output voltage rises monotonically and
it does not overshoot its final voltage by more than 5%.
POWER MANAGEMENT
Applications Information
2005 Semtech Corp.
CONTROL1
CONTROL2
Figure 11. Sequencing the Outputs by (a) Delaying Release of one Channel Relative to
CONTROL1
CONTROL2
FB
is still below 0.74V, then the
the Other and (b) Using the PGOOD of one Channel to Control the Other.
CSS1
CSS2
OFF
OFF
SS
is charged above 2V.
SS
SS1
SS2
T D
ON
< 2V), the overload
SC2440
(a)
ON
PGOOD1
PGOOD2
SS
17
When starting into a shorted output, the SC2440 will
repeatedly start and shut off (“hiccup”). V
will appear as asymmetrical triangular waves [Figure
10(b)].
Power Good Indicators
The PGOOD pins (Pins 11 and 14) are the open-collector
outputs of the power good comparators. These slow
comparators are incorporated with small amount of
hysteresis. The FB low-to-high trip voltage of the power
good comparators is 90% of the final regulation voltage.
A pull-up resistor from each PGOOD pin to the input supply
or the regulator output set the logic high level of the
comparator.
The power good comparator output becomes valid
provided that V
good output is actively pulled low. A power good pull-up
resistor tied to the input will therefore increase current
drain during shutdown. Tying the power good pull-up
resistor to the regulator output is preferred, as this will
minimize the shutdown supply current. In shutdown there
OFF
ON
IN
is above 0.9V. In shutdown the power
CSS1
CSS2
PGOOD1
SS1
SS2
SC2440
PGOOD2
(b)
www.semtech.com
SC2440
SS
and V
COMP