ST STEVAL-L6982CDR, Руководство пользователя

Страница: 3 / 15

1.4 Connectors and test points
• V
IN
- Tp3 : connect to the positive terminal of a supply voltage (from 6 V to 38 V with default 5 V V
OUT
).
Input voltage is filtered (see Section 1.5 ) to decrease the EMI. Supply voltage should be set with a current
limitation compatible with the power board request. Typically,
I
limit
> V
OUT
× I
OUT
/V
IN
.
• GND - Tp4, Tp3 : return of terminal of input and output capacitors.
• V
OUT
- Tp6 : connect to the positive terminal of the active load or to a power resistor between V
OUT
and
GND.
Important:
For all the above connections, short wires are recommended to avoid oscillation between the cable parasitic inductance and
the input capacitor.
• ENABLE : the device starts the switching activity once the Enable pin rises over the wake-up threshold
(1.2 V); thus, defining R4/R5 resistor ratio, it is possible to program the UVLO threshold. By default, the
STEVAL-L6982CDR Enable pin is pulled up to V
IN
with R4 = 10 K and R5 not mounted. Consequently, it is
possible to disable the output voltage regulation driving the Enable test point to GND. Vice versa the system
starts up once the Enable test point is left floating.
For further details, see
L6982 datasheet .
• CLK_IN : using L6982
N
DR (low
noise
mode), it is possible to synchronize with an external clock. For further
details, see L6982 datasheet .
1.5
1.6
1.6.1
Input EMI filter
The STEVAL-L6982CDR is compliant with CISPR16-4-2.
An input filter helps to reduce EMI. The filter consists of a ferrite bead (L3), an inductor (L4) and three ceramic
capacitors (C11, C12 and C14).
An electrolytic capacitor is used for bulk energy storage and input damping.
V
OUT
settings
By default, the STEVAL-L6982CDR is with V
OUT
= 5 V but the output voltage can be managed from 0.85 V to a
higher voltage by selecting the right output partition resistors (R2 and R3):
V
OUT
= R2 + R3 /R3 × V
FB
where V
FB
is the fix to 0.85 V.
Once V
OUT
has been changed, it is possible to increase the system performance in term of bandwidth.
We recommend eDesignSuite to select the compensation value (C8, R2 and R3), inductors and C
OUT
value.
eDesignSuite
The eDesignSuite software tool developed by STMicroelectronics helps you configure ST products for power
conversion applications.
You can use it to customize your board for a specific application. After entering the main specifications for your
design, you can generate an automatic design or follow a sequential process to build a highly customized design.
UM2918
Connectors and test points
UM2918 - Rev 1
page 3/15