Application Notes
PT4210 Series
Using the Remote On/Off Function on the
PT4210 Isolated 7W DC/DC Converters
Applications requiring output voltage On/Off control, the
PT4210 DC/DC converter series incorporates a
“Remote
On/Off”
control (pin 11). This feature can be used when
there is a requirement for the module to be switched off
without removing the applied input source voltage.
The converter functions normally with Pin 11 open-circuit,
providing a regulated output voltage when a valid source
voltage is applied to +V
in
(pin 18), with respect to –V
in
(pin 17). When a low-level
1
ground signal is applied to
pin 11, the converter output will be turned off.
Figure 1 shows an application schematic, which details
the typical use of the
Remote On/Off
function. Note the
discrete transistor (Q1). The control pin has its own
internal pull-up, and must be controlled with an open-
collector or open-drain device (See notes 2 & 3). Table 1
gives the input requirements.
When placed in the “Off” state, the standby current drawn
from the input source is typically reduced to less than 1mA.
Table 1; Remote On/Off Control Requirements
1
Parameter
Disable
Enable
Vo/c [Open-Circuit]
Iin [pin 11 at –Vin]
Min
-0.1V
5.0V 3
—
—
Typ
—
—
—
–100µA
Max
1.0V
Open-Circuit 2
10V
—
Series
PT4210
V
in
Range
38 – 75V
UVLO Threshold
36V ±2V
Figure 1
+ V
in
-V
in
Note 1
18
17
+Vin
+Vout
1
2
+V
o
-V
o
PT4210
-Vin
Remote
On/Off*
11
-Vout
1 =OFF
Q1
BSS138
Note 1
Vdd
R1
10k
U1a
#
D1
1N4148
#
Note 1
or similar low-leakage PIN diode
Notes:
1. The
Remote On/Off
control uses –V
in
(pin 17) as its ground
reference. All voltages specified are with respect to –V
in
.
2. Use an open-collector device (preferably a discrete
transistor) for the
Remote On/Off
input. Do not connect a
pull-up resistor directly to pin 11.
3. The
Remote On/Off
pin may be controlled with devices that have
a totem-pole output providing that a blocking diode is
used (See Figure 1). The blocking diode is required to
prevent current from being injected into On/Off control
pin.
Note: For TTL devices a pull-up may be required on the
cathode side of the blocking diode. This is to guarantee a
minimum enable voltage at pin 11 (See Figure 1).
4. The PT4210 converters incorporate an “Under-Voltage
Lockout” (UVLO). The UVLO will keep the module off
when the input voltage to the converter is low, regardless of
the state of the
Remote On/Off
control. Table 2 gives the
UVLO input voltage thresholds.
Table 2; UVLO Thresholds
4
Turn-On Time:
In the circuit of Figure 1, turning Q
1
on applies a
low-voltage to pin 11 and disables the converter output.
Correspondingly, turning Q
1
off allows pin 11 to be pulled
high by an internal pull-up resistor. The converter produces a
regulated output voltage within 50ms. Although the rise-
time of the output is short (<1ms), the delay time will vary
depending upon the input voltage and the module’s internal
timing. Figure 2 shows shows an example of the output
response for a PT4213 (5.0V), following the turn-off of
Q
1
at time t =0. The waveform was measured with a 48Vdc
input voltage, and 1.2Adc resistive load.
Figure 2
V
O
(2V/Div)
delay time
0
5
10
15
20
25
30
time (milli-secs)
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