TPS7H5005-SEP, TPS7H5006-SEP, TPS7H5007-SEP, TPS7H5008-SEP
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SLVSGG1 – FEBRUARY 2022
For different power converter topologies, the primary change to the compensation selection procedure will be the
determination of the power stage transconductance gmPS. The power stage transconductance can be calculated
as shown in Equation 23.
NP × NCSS
gmPS
=
CCSR × RCS × NS × NCSP
(23)
where:
•
•
•
•
•
•
NP is the number of primary turns on the main power transformer (set to 1 if no transformer is used)
NS is the number of secondary turns on the main power transformer (set to 1 if no transformer is used)
NCSP is the number of primary turns on the current sense transformer (set to 1 if no transformer is used)
NCSS is the number of secondary turns of the current sense transformer (set to 1 if no transformer is used)
RCS is the selected value of the current sense resistor
CCSR is the ratio to COMP of CS_ILIM
Note that for the TPS7H500x-SEP, the sensed current waveform is compared to the voltage at COMP divided
down by the factor CCSR at the PWM comparator, which is accounted for in the denominator of the equation.
For buck converters, all turns for the main power transformer can be set equal to 1 and the equation still applies.
8.3.19 Thermal Shutdown
The internal thermal shutdown circuitry forces the device to stop switching if the junction temperature exceeds
175°C (typical). The device reinitiates the power-up sequence when the junction temperature drops below 160°C
(typical).
8.4 Device Functional Modes
The TPS7H500x-SEP series uses fixed frequency, peak current mode control. Each controller regulates the
peak current and duty cycle of the converter. The internal oscillator initiates the turn-on of the primary output
used as the gate driver input for the power switch. The external power switch current is sensed through an
external resistor and compared via internal comparator. The voltage generated at the COMP pin is stepped
down via internal resistors. When the sensed current reaches the stepped down COMP voltage, the power
switch is then turned off.
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