Data Sheet
Austin LynxTM II SMT Non-isolated Power Modules:
August 28, 2009
2.4 – 5.5Vdc input; 0.75Vdc to 3.63Vdc Output; 10A output current
Feature Description
VIN+
MODULE
Remote On/Off
R
pull-up
The Austin LynxTM II SMT power modules feature an
On/Off pin for remote On/Off operation. Two On/Off
logic options are available in the Austin LynxTM II series
modules. Positive Logic On/Off signal, device code
suffix “4”, turns the module ON during a logic High on
the On/Off pin and turns the module OFF during a logic
Low. Negative logic On/Off signal, no device code
suffix, turns the module OFF during logic High on the
On/Off pin and turns the module ON during logic Low.
I
ON/OFF
ON/OFF
+
PWM Enable
V
ON/OFF
R1
R2
Q2
CSS
Q1
GND
_
For positive logic modules, the circuit configuration for
using the On/Off pin is shown in Figure 29. The On/Off
pin is an open collector/drain logic input signal (Von/Off)
that is referenced to ground. During a logic-high
(On/Off pin is pulled high internal to the module) when
the transistor Q1 is in the Off state, the power module is
ON. Maximum allowable leakage current of the
transistor when Von/off = VIN,max is 10µA. Applying a
logic-low when the transistor Q1 is turned-On, the
power module is OFF. During this state VOn/Off must
be less than 0.3V. When not using positive logic On/off
pin, leave the pin unconnected or tie to VIN.
Figure 30. Circuit configuration for using negative
logic On/OFF.
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. The typical average output current during hiccup
is 3.0A.
VIN+
MODULE
R2
Input Undervoltage Lockout
ON/OFF
Q2
+
R1
At input voltages below the input undervoltage lockout
limit, module operation is disabled. The module will
begin to operate at an input voltage above the
undervoltage lockout turn-on threshold.
V
ON/OFF
I
ON/OFF
PWM Enable
R3
R4
Q1
Overtemperature Protection
Q3
CSS
To provide protection in a fault condition, the unit is
equipped with a thermal shutdown circuit. The unit
will shutdown if the thermal reference point Tref,
exceeds 125oC (typical), but the thermal shutdown is
not intended as a guarantee that the unit will survive
temperatures beyond its rating. The module will
automatically restarts after it cools down.
GND
_
Figure 29. Circuit configuration for using positive
logic On/OFF.
Output Voltage Programming
For negative logic On/Off devices, the circuit
The output voltage of the Austin LynxTM II SMT can be
programmed to any voltage from 0.75 Vdc to 3.63 Vdc
by connecting a single resistor (shown as Rtrim in
Figure 31) between the TRIM and GND pins of the
module. Without an external resistor between the TRIM
pin and the ground, the output voltage of the module is
0.7525 Vdc. To calculate the value of the resistor Rtrim
for a particular output voltage Vo, use the following
equation:
configuration is shown is Figure 30. The On/Off pin is
pulled high with an external pull-up resistor (typical Rpull-
up = 5k, +/- 5%). When transistor Q1 is in the Off state,
logic High is applied to the On/Off pin and the power
module is Off. The minimum On/off voltage for logic
High on the On/Off pin is 1.5Vdc. To turn the module
ON, logic Low is applied to the On/Off pin by turning ON
Q1. When not using the negative logic On/Off, leave
the pin unconnected or tie to GND.
21070
⎡
⎤
Rtrim =
−5110 Ω
⎢
⎥
Vo − 0.7525
⎣
⎦
LINEAGE POWER
12
LINEAGEPOWER [ LINEAGE POWER CORPORATION ]
