STV7801 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
STV7801 Datasheet PDF : 18 Pages
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STV7801S
The diodes for the recirculation current directly im-
pact the device performances. High Voltage di-
odes with recovery time inferior to 50ns are recom-
mended. Shorter recovery times will improve the
power efficiency of the application.
The rise and fall time of the output signal is adjust-
ed by the value of the inductance for a given ca-
pacitive load.
trise (tfall) is calculated by the following formula :
trise= πx LxCload
A 1nF bootstrap capacitor is recommended. The
bootstrap capacitor allows the output signal to
reach the Vpp value. For a given output level, the
power efficiency will be increased.
A 47µF capacitor is recommended. The ripple on
the tank capacitor is reduced by increasing the
tank capacitor value.
Decoupling capacitors on the power supplies will
minimise the overshoots.
The timing of the control signals will be adjusted by
the trimmers of the RC cells. It is recommended to
enable the clamp signals (H-Clmp, L-Clmp) after
the rising (falling) edge of the output signal has
reached its maximum (minimum) value.
14 - RECOVERY FACTOR MEASUREMENT CONDITIONS
An idealised schematic of the Power Recovery application is defined below. The inductance (power sav-
ing mode) and the 2 capacitors (load, floating_supply) are external components for the D.P.S. device.
Figure 4. DPS Device : Functional Diagram
Vpp
S3
Cfloating_supply
S4
A
S1
Inductance
(Power Saving Mode)
Cload
S2
Vssp
The Power Recovery Factor (PRF) in % is given
by the formula :
PRF = 100 x (Pc - Pr) / Pc.
– Pc is the theoretical capacitive power dissipated
in the switches S1, S2 of the Data Power Switch
device when S3, S4 are not activated. Pc is cal-
culated by the formula :
2
PC = Cload × Vpp xF
with F=switching frequency.
Cload = equivalent panel capacitance
– Pr is the power dissipated in the Data Power
Switch device when it is configured in a power re-
covery mode (S1, S2, S3, S4 activated). Pr is
calculated by multiplying the average current giv-
en by the current sensor A and the value of the
supply voltage Vpp.
PRF is affected by the external components of the
DPS device such as the inductance and the de-
coupling capacitors, also the layout of the applica-
tion.
12/18
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