UC1846-SP_15 Datasheet, PDF (13/29 Pages) Texas Instruments – Current-Mode PWM Controller

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Feature Description (continued)
UC1846-SP
SLUS871C – JANUARY 2009 – REVISED OCTOBER 2015
Figure 7. Shutdown Latch
Referring to Figure 11, if
V_{REF < 0.8mA}
R1
(2)
the shutdown latch commutates when ISS = 0.8 mA and a restart cycle initiates.
Referring to Figure 12, if
V_{REF > 3mA}
R1
(3)
the device latches off until power is recycled.
7.3.8 Output Section
UC1846-SP incorporates high current dual totem pole output stage capable of sourcing/sinking 1.5 A peak
current for fast switching of power MOSFETs and limited to 0.5 A dc current.
7.3.9 Undervoltage Lockout
Minimum input voltage for converter is 8 V or higher, with typical value being 7.7 V. At input voltages below the
actual UVLO voltage, the devices will not operate.
7.3.10 Soft-Start
Connecting a capacitor from CL/SS pin 1 to ground which is charged by 0.5-mA internal current source will
determine the soft-start time. If over current is also implemented as shown in Figure 6, then SS charge time will
be determined by charging SS capacitor by 0.5-mA current as well as current contributed by R1 resistor in
charging the SS capacitor.
7.4 Device Functional Modes
7.4.1 Operation With V_IN < 8 V (Minimum V_IN)
The devices operate with input voltages above 8 V. The maximum UVLO voltage is 8 V and will operate at input
voltages above 8 V. The typical UVLO voltage is 7.7 V and the devices may operate at input voltages above that
point. The devices also may operate at lower input voltages, the minimum UVLO voltage is not specified. At input
voltages below the actual UVLO voltage, the devices will not operate.
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