EPC700 EPC [Espros Photonics corp], EPC700 Datasheet - Page 6

• Manufacturer Part Number: EPC700
• Description: 24V/50mA General-Purpose Output-Driver
• Manufacturer: EPC [Espros Photonics corp]

Application Information
epc700 and epc702 have two modes of operation, where the SENS pin is used to define the mode. When SENS is tied to VDD, the chip
operates as a sink driver capable to sink max. 50mA at 30VDC (refer to Figure 6). The load is connected directly between V
If the current through the internal switch exceeds I
If the SENS pin is at low level, the OUT pin is driven by a source driver also capable to drive 50mA into an external power transistor. This
mode is used if the required output current has to be higher than 50mA, e.g. 1A and the output voltage exceeds 30VDC (refer to Figure 7).
The load current is measured by monitoring the voltage drop over a resistor. If the internal switch is used, also the current measurement
resistor is located internally (Figure 6). In the case of using an external power transistor as shown in Figure 7, the current measurement
resistor R
diagrams of the signals can be found in section “Functional Description”.
The IN signal must be low during power-up (t
external active driving is needed during startup.
epc700 or epc702 Using the Internal Switch
Figure 6 shows the epc700/702 in the mode using the internal switch. To enable this
mode, the SENS pin has to be connected to VDD. Note that the VDD of the chip and
V
between 9.6 and 30V.
The factor f
not to damage the chip due to overheating. This factor has to be higher than 1,000. In
the worst case scenario a peak current of approx. 0.5A is flowing from V
the chip with a t
case is smaller then 50ms, the average power dissipation would exceed the safe
operation condition and the device will get damaged.
The diode D
loads are turned off.
R1 is to protect the internal switch in case of a short circuit on the load when a very
low impedance power supply is used.
The voltage V
above the maximum value of 'Supply Voltage' stated in the table Electrical Characte-
ristics.
epc700 or epc702 Using an External Switching Transistor
Figure 7 shows the operation mode using an external switch T
output current/voltage drive capability. In this example, a bipolar transistor is used,
whereas the base current is limited by the resistor R
50mA. In order not to damage the chip, the user has to select the resistor R
chip does not need to drive more than 50mA. Other possible switches are a NPN BJT
or an n-channel MOSFET.
The load is turned on and off by setting the pin IN to high respectively to low level.
When the load is turned on, the load current flows from V
through the transistor T
resulting voltage is applied to pin SENS, which measures the voltage drop. If it
exceeds the threshold of an internal comparator, set to 200mV, the output is turned off
after the given delay time t
If the delay time should be extended to a value above the possible settings of t
to Table 3), an RC network can added, designated as R
additional time delay t
varies according to the current through R
when a large capacitor in the load path needs to be charged. The additional delay in
the over-current detection helps in such a situation.
Note that the VDD of the chip and V
tions. The value of VDD must be between 9.6 and 30V. V
which is appropriate to the external switching transistor.
The diode D
© 2011 ESPROS Photonics Corporation
Characteristics subject to change without notice
L
at the load can have a different value. The values for both VDD and V
S
has to be placed externally. If the voltage drop at R
rt
1
1
is to protect the transistor T
between minimum off-time and delay-time must be maintained in order
L
is to protect the internal switch against voltage surges when inductive
can be higher than VDD in this configuration. However, it must not be
Del
set at 50μs if a short-circuit occurs. If the recovery time t
IN
STATUS
ext
epc700
epc702
1
GND
VDD
GND
VDD
to GND. This current creates a voltage drop over R
can be calculated approx. as R
del
.
SENSE
OUT
L
on the load are different in most of the applica-
1
R1≥50Ω
against voltage surges when inductive loads are turned off.
S
. This design concept is especially useful,
STARTUP
SENS
V
L
D
≤VDD max
L
, the switch is turned off.
) for proper function of the chip. The epc70x has a built in pull down resistor, so not
B
. The maximum base current is
R
L
L
L
through the resistor R
T
T
instead, can be on a level
and C
x C
S
1
exceeds the threshold of 200 mV, the output stage is deactivated. The timing
in order to extend the
T
. However, the time
T
in Figure 7. The
6
L
L
at 30V into
B
need to be
minoff
such that
del
S
in this
. The
(refer
S
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File: Unbenannt
and
In case of a short-circuit in the load the turn-off delay
Figure 6: epc700 or epc702 using the internal switch
This network adds t
Figure 7: epc700 or epc702 operation mode
can be extended by an external RC network.
IN
STATUS
using an external switching transistor.
to drive a load of up to 50mA /30VDC
IN
STATUS
epc700
epc702
GND
VDD
epc700
epc702
VDD
GND
VDD
GND
VDD
GND
SENSE
SENSE
OUT
OUT
ext
Datasheet epc700_702 - V2.2
to the internal delay t
epc700/epc702
Dieter Kägi
R1≥50Ω
R1
C
T
L
R
and the OUT pin.
T
V
D
L
www.espros.ch
≤VDD max
L
D
V
L
T1
L
R
R
L
SENSE
del
.
R
L
25.05.2011
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