CPC1580P IXYS, CPC1580P Datasheet - Page 7

• Manufacturer Part Number: CPC1580P
• Manufacturer: IXYS

Specifications of CPC1580P

• Lead Free Status / RoHS Status: Supplier Unconfirmed

3.2 Transistor Selection
The CPC1580 charges and discharges an external
MOSFET transistor. The selection of the MOSFET is
determined by the user to meet the specific power
requirements for the load. The CPC1580 output
voltage is listed in the specifications, but as mentioned
earlier, there must be little or no gate leakage.
Another parameter that plays a significant role in the
selection of the transistor is the gate drive voltage
available from the part. The CPC1580 uses
photovoltaic cells to collect the optical energy
generated by the LED; to generate more voltage, the
photovoltaic diodes are stacked. The voltage change
of the photovoltaic stack reduces with increased
temperature. The user must select a transistor that will
maintain the load current at the maximum
temperature, given the V
CPC1580 Table of Electrical Specifications.
The example circuits shown in
use “logic level” MOSFETs for each design to maintain
the load described.
The primary characteristics of the application
switching are t
time of the storage capacitor, t
are dependent on the MOSFET selection and need to
be reviewed in light of the application requirements.
The CPC1580 turns on the MOSFET transistor to the
specified V
delay is the amount of time until the LED is turned off
and the capacitive load discharges to the level in the
CPC1580 specification. For MOSFETs with larger or
smaller required gate charge the t
proportionately faster and slower, but it is not a linear
relationship.
To calculate the nominal rise time of the transistor's
drain voltage, V
To calculate the nominal fall time of the transistor's
drain voltage, V
Where C
(averaged over the switching voltage range) found in
the MOSFET data sheet, I
current of the CPC1580, and I
driving ability. The maximum value of t
R00G
t
3.2.1 Transistor Switching Characteristics
t
RISE,VD
FALL,VD
RSS
GS
~ ~
~ ~
is the MOSFET gate-drain capacitance
after the t
V
ON
V
I
D
D
LOAD
LOAD
G_SOURCE
:
:
, t
I
G_SINK
OFF
• C
• C
, t
RSS
RSS
ON
RISE
GS
G_SINK
delay. Similarly the t
in
, t
CHG
G_SOURCE
Section
FALL
Figure 1
is the gate sinking
ON
. These parameters
, and the recovery
(SECONDS)
(SECONDS)
and t
RISE
1.6, the
and
is the gate
OFF
is limited
Figure 2
will be
OFF
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by the CPC1580 unloaded discharge characteristic
and should be reviewed in light of the final application
component selections if critical.
The value for the charge time, T
component selection. The storage capacitor charge
recovery time (seconds) is computed as:
Which reduces to:
R
elements that are present in the application circuit
diagram (see
The term inside the logarithm reflects the discharge
and recharge voltage on C
component selection, this can be simplified as
described above.
Use this information to calculate the maximum
switching frequency in
t
CHG
OVP
~ ~
Note:
remote power is otherwise unavailable. If the
LED is also powered remotely, care must be
taken to ensure that parasitic transient signals
are reliably filtered from the input control signal.
Large transient currents will mutually couple
energy between cables and a simple R-C
filtering of the CPC1580 input may be sufficient
to suppress false turn-on.
and C
- (400 + R
t
CHG
The CPC1580 is ideal to use where
OVP
Figure
OVP
~ ~
are optional over-voltage protection
) • (C
- (400 + R
ST
2).
Section 6
+ C
OVP
OVP
ST
) • (C
. For practical circuit
) • ln
CHG
ST
(
below.
+ C
(V
, is due to external
LOAD
OVP
) • 3
- V
Q
GATE
FINAL
CPC1580
) • C
ST
)
7