GE Industrial Solutions 12V MicroTLynx 12A - Manual (Page 15)

GE
Data Sheet
12V MicroTLynx TM 12A: Non-Isolated DC-DC Power Modules
4.5Vdc –14Vdc input; 0.69Vdc to 5.5Vdc output; 12A Output Current
May 2, 2013 ©2013 General Electric Company. All rights reserved. Page 15
Feature Descriptions
Remote Enable
The 12V Micro TLynx TM modules feature an On/Off pin for remote
On/Off operation. Two On/Off logic options are available. In the
Positive Logic On/Off option, (device code suffix “4” see Ordering
Information), the module turns ON during a logic High on the
On/Off pin and turns OFF during a logic Low. With the Negative
Logic On/Off option, (no device code suffix see Ordering
Information), the module turns OFF during logic High and ON
during logic Low. The On/Off signal is always referenced to
ground. For either On/Off logic option, leaving the On/Off pin
disconnected will turn the module ON when input voltage is
present.
For positive logic modules, the circuit configuration for using the
On/Off pin is shown in Figure 42. When the external transistor
Q1 is in the OFF state, the internal PWM Enable signal is pulled
high through an internal 24.9k
Ω resistor and the external pullup
resistor and the module is ON. When transistor Q1 is turned ON,
the On/Off pin is pulled low and the module is OFF. A suggested
value for R
pullup
is 20k Ω.
Figure 42. Circuit configuration for using positive On/Off
logic.
For negative logic On/Off modules, the circuit configuration is
shown in Fig. 43. The On/Off pin should be pulled high with an
external pull-up resistor (suggested value for the 4.5V to 14V
input range is 20Kohms). When transistor Q1 is in the OFF state,
the On/Off pin is pulled high, internal transistor Q2 is turned ON
and the module is OFF. To turn the module ON, Q1 is turned ON
pulling the On/Off pin low, turning transistor Q2 OFF resulting in
the PWM Enable pin going high and the module turning ON.
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.
Figure 43. Circuit configuration for using negative On/Off
logic.
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 133 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 Micro TLynx TM module can be
programmed to any voltage from 0.69dc 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
3.3V and higher, the input voltage needs to be larger than the
minimum of 4.5V.
Without an external resistor between Trim and GND pins, the
output of the module will be 0.69Vdc. To calculate the value of
the trim resistor, Rtrim for a desired output voltage, use the
following equation:
( )
Ω






−
= k
Vo
Rtrim
69 . 0
9 . 6
Rtrim is the external resistor in kΩ, and Vo is the desired output
voltage.
25.5K
Q1
ON/OFF
VIN+
GND _
+
PWM Enable
V
ON/OFF
MODULE
I
Rpullup1
ON/OFF
22K
Q2
23K
11.8K
23K
I
ON/OFF
25.5K
Q1
GND
ON/OFF
VIN+
_
+
PWM Enable
V
ON/OFF
MODULE
Rpullup
22K
Q3
22K
11.8K
Q2
22K