Datasheet

 
SLUS544E − SEPTEMBER 2003 − REVISED MARCH 2009
7
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Terminal Functions
TERMINAL
PIN NUMBER
FUNCTION
UCC28220D
UCC28220PW
UCC28221D UCC28221PW
NAME I/O
FUNCTION
1 1 2 LINEOV I Input for line over voltage comparator
2 2 3 LINEHYS I Sets line comparator hysteresis
3 3 4 VDD I Device supply input
4 4 5 CS1 I Channel 1 current sense input
5 5 6 SLOPE I Sets slope compensation
6 6 7 CS2 I Channel 2 current sense input
7 7 8 SS I Soft-start input
8 8 9 CTRL I Feedback control input
9 9 12 DISCHG I Sets oscillator discharge current
10 10 13 CHG I Sets oscillator charge current
11 11 14 GND − Device ground
12 12 15 OUT2 O PWM output from channel 2
13 13 16 OUT1 O PWM output from channel 1
14 14 17 REF O Reference voltage output
15 15 18 LINEUV I Input for line under voltage comparator
− 16 20 VIN I High voltage start-up input
16 − 1, 10, 11, 19 N/C − No connection
PIN DESCRIPTIONS
VDD: This is used to supply power to the device, monitoring this pin is a the UVLO circuit. This is used to insure
glitch-free startup operation. Until VDD reaches its UVLO threshold, it remains in a low power mode, drawing
approximately 150 µA of current and forcing pins, SS, CS1, CS2, OUT1, and OUT2 to logic 0 states. If the VDD
falls below 8 V after reaching turn-on, it will go back into this low power state. In the case of the UCC28221, the
UVLO threshold is 13 V. It is 10 V for the UCC28220. Both versions have a turn-off threshold of 8 V.
VIN (UCC28221 only): This pin has an internal high voltage JFET used for startup. The drain is connected to
VIN, while its’ source is connected to VDD. During startup, this JFET delivers 12 mA typically with a minimum
of 4 mA to VDD, which in turn, charges up the VDD bypass capacitor. When VDD gets to 13 V, the JFET is turned
off.
CS1 and CS2: These 2 pins are the current sense inputs to the device. The signals are internally level shifted
by 0.5 V before the signal gets to the PWM comparator. Internally the slope compensation ramp is added to this
signal. The linear operating range on this input is 0 to 1.5 V. Also, this pin gets pulled to ground each time its
respective output goes low. (ie: OUT1 and OUT2).
SLOPE: This pin sets up a current used for the slope compensation ramp. A resistor to ground sets up a current,
which is internally divided by 25 and then applied to an internal 10-pF capacitor. Under normal operation th dc
voltage on this pin is 2.5 V..
SS: A capacitor to ground sets up the soft-start time for the open loop soft-start function. The source and sink
current from this pin is equal to 3/7th of the oscillator charge current set by the resistor on the CHG pin. The
soft start capacitor is held low during UVLO and during a Line OV or UV condition. Once an OV or UV fault
occurs, the soft-start capacitor is discharged by a current equal to its charging current. The capacitor does NOT
quickly discharge during faults. In this way, the controller has the ability to recover quickly from very short line
transients. This pin can also be used as an Enable/Disable function.