GE Industrial Solutions 12V PicoTLynx 3A - Manual (Page 14)

GE
Data Sheet
12V PicoTLynx TM 3A: Non-Isolated DC-DC Power Modules
4.5Vdc –14Vdc input; 0.59Vdc to 5.5Vdc output; 3A Output Current
May 2, 2013 ©2013 General Electric Company. All rights reserved. Page 14
1.5MEG
Q2
GND
VIN+
ON/OFF
PWM Enable
+
_
ON/OFF
V
I
MODULE
Rpullup1
ON/OFF
22K
Q1
22K
Figure 43. Circuit configuration for using negative On/Off
logic.
Overcurrent Protection
To provide protection in a fault (output overload) condition,
the unit is equipped with internal current-limiting circuitry
and can endure current limiting continuously. At the point of
current-limit inception, the unit enters hiccup mode. The unit
operates normally once the output current is brought back
into its specified range.
Over Temperature Protection
To provide protection in a fault condition, the unit is
equipped with a thermal shutdown circuit. The unit will
shutdown if the overtemperature threshold of 140 o C is
exceeded at the thermal reference point T
ref.
The thermal
shutdown is not intended as a guarantee that the unit will
survive temperatures beyond its rating. Once the unit goes
into thermal shutdown it will then wait to cool before
attempting to restart.
Input Undervoltage Lockout
At input voltages below the input undervoltage lockout limit,
the module operation is disabled. The module will begin to
operate at an input voltage above the undervoltage lockout
turn-on threshold.
Output Voltage Programming
The output voltage of the 12V PicoTLynx TM 3A module can
be programmed to any voltage from 0.59dc to 5.5Vdc by
connecting a resistor between the Trim and GND pins of the
module. Certain restrictions apply on the output voltage set
point depending on the input voltage. These are shown in
the Output Voltage vs. Input Voltage Set Point Area plot in
Fig. 44. The Upper Limit curve shows that for output
voltages of 0.9V and lower, the input voltage must be lower
than the maximum of 14V. The Lower Limit curve shows
that for output voltages of 3.8V and higher, the input voltage
needs to be larger than the minimum of 4.5V.
0
2
4
6
8
10
12
14
16
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
Output Voltage (V)
In
p
u
t V
o
lt
a
g
e
(
v
)
Lower Limit
Upper Limit
Figure 44. Output Voltage vs. Input Voltage Set Point Area
plot showing limits where the output voltage can be set
for different input voltages.
Without an external resistor between Trim and GND pins,
the output of the module will be 0.59Vdc. To calculate the
value of the trim resistor, Rtrim for a desired output voltage,
use the following equation:
( )
Ω






−
= k
Vo
Rtrim
591 . 0
91 . 5
Rtrim is the external resistor in kΩ
Vo is the desired output voltage.
Table 1 provides Rtrim values required for some common
output voltages.
Table 1
V
O, set
(V) Rtrim (KΩ)
0.6 656.7
1.0 14.45
1.2 9.704
1.5 6.502
1.8 4.888
2.5 3.096
3.3 2.182
5.0 1.340
By using a ±0.5% tolerance trim resistor with a TC of
±100ppm, a set point tolerance of ±1.5% can be achieved as
specified in the electrical specification.
Remote Sense
The 12V PicoTLynx TM 3A modules have a Remote Sense
feature to minimize the effects of distribution losses by
regulating the voltage at the SENSE pin. The voltage
between the SENSE pin and VOUT pin must not exceed 0.5V.
Note that the output voltage of the module cannot exceed
the specified maximum value. This includes the voltage drop
between the SENSE and Vout pins. When the Remote Sense
feature is not being used, connect the SENSE pin to the
VOUT pin.