SRK2000 STMicroelectronics, SRK2000 Datasheet - Page 8

• Manufacturer Part Number: SRK2000
• Description: SYNCHRONOUS RECTIFIER SMART DRIVER FOR LLC RESONANT CONVERTER
• Manufacturer: STMicroelectronics

Application information
5
5.1
5.1.1
8/17
Application information
EN pin: pin function and usage
This pin can perform three different functions: it sets the threshold V
to-source voltage of either synchronous rectifier (SR) Power MOSFET to determine their
turn-off in each conduction cycle; it allows the user to program the UVLO thresholds of the
gate drivers and can be used as Enable (remote on/off control).
Pull-up resistor configuration
At startup, an internal 10 µA current sink (I
Vcc is below the startup threshold V
voltage V
of both synchronous rectifiers during their cycle-by-cycle operation: if V
V) the threshold is set at -25 mV, otherwise at -12 mV. Once the decision is made, the
setting is frozen as long as Vcc is greater than the turn-off level V
A simple pull-up resistor R
voltage on the EN pin as the device turns on is given by:
Then, considering worst-case scenarios, we have:
Some additional margin (equal to the resistor's tolerance) needs to be considered;
assuming 5% tolerance, the use of the standard values R
= 270 kΩ in the second case, is suggested.
Figure 5.
As Vcc exceeds V
is activated. The voltage on the pin is then compared to an internal reference V
EN
on the EN pin determines the turn-off threshold V
EN pin biased with a pull-up resistor (for logic-level MOSFET driving)
CCOn
, the internal current sink I
R
R
1
1
1
to Vcc can be used to set V
>
<
Doc ID 17811 Rev 2
633
296
k
k
V
CCOn
Ω
Ω
EN
=
→
→
. The moment Vcc equals V
V
EN
CCOn
) is active as long as the device supply voltage
V
V
DVS
DVS
−
EN
1
1
I
2 ,
2 ,
EN
_
_
is switched off and the enable function
Off
Off
R
1
DVS1,2_Off
=
=
1
−
−
= 680 kΩ in the first case and R
25
12
DVS1,2_Off
mV
mV
CCOff
turn-off threshold. The
DVS1,2_Off
CCOn
EN
(4.25 V typ.).
for the drain voltage
< V
(4.5 V typ.), the
EN_Th
for the drain-
EN_On
SRK2000
(= 0.36
set at
1