Datasheet

UCC28700, UCC28701
UCC28702, UCC28703
www.ti.com SLUSB41 – JULY 2012
Current and Voltage Scaling Terms
• K
AM
: maximum-to-minimum peak primary current ratio (see ELECTRICAL CHARACTERISTICS).
• K
LC
: current-scaling constant (see ELECTRICAL CHARACTERISTICS).
Transformer Terms
• L
P
: transformer primary inductance.
• N
AS
: transformer auxiliary-to-secondary turns ratio.
• N
PA
: transformer primary-to-auxiliary turns ratio.
• N
PS
: transformer primary-to-secondary turns ratio.
Power Terms in Watts
• P
IN
: converter maximum input power.
• P
OUT
: full-load output power of the converter.
• P
RSTR
: VDD start-up resistor power dissipation.
• P
SB
: total stand-by power.
• P
SB_CONV
: P
SB
minus start-up resistor and snubber losses.
Resistance Terms in Ω
• R
CS
: primary current programming resistance.
• R
ESR
: total ESR of the output capacitor(s).
• R
PL
: preload resistance on the output of the converter.
• R
S1
: high-side VS pin resistance.
• R
S2
: low-side VS pin resistance.
• R
STR
: maximum start-up resistance to achieve the turn-on time target.
• R
STR
: V
DD
start-up resistance.
Timing Terms in Seconds
• T
D
: current-sense delay including MOSFET turn-off delay; add 50 ns to MOSFET delay.
• T
DMAG(min)
: minimum secondary rectifier conduction time.
• T
ON(min)
: minimum MOSFET on time.
• T
R
: resonant frequency during the DCM (discontinuous conduction mode) time.
• T
STR
: converter start-up time requirement.
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