PTB48500_15 Datasheet, PDF (6/17 Pages) Texas Instruments – 48-V INPUT ISOLATED DC/DC CONVERTER

PTB48500 ^{PTB48500A and PTB48502A are Not Recommended for New Designs}
PTB48501
PTB48502
SLTS218C – SEPTEMBER 2003 – REVISED AUGUST 2006
www.ti.com
DEVICE INFORMATION
TERMINAL FUNCTIONS
TERMINAL
NAME
NO.
+V_I ⁽¹⁾
1
–V_I
5
V_O1
10
V_O2
6
COM
7
V_O2 Adjust
9
Enable ⁽²⁾
3
EN Out
4
Sync Out
2
POR ⁽³⁾/COM ⁽⁴⁾
8
DESCRIPTION
The positive input supply for the module with respect to –V_I. When powering the module from a –48 V telecom
central office supply, this input is connected to the primary system ground.
The negative input supply for the module, and the 0 VDC reference for the Enable, EN Out, and Sync Out
signals. When the module is powered from a +48-V supply, this input is connected to the 48-V Return.
The higher regulated power output voltage, which is referenced to the COM node.
The lower regulated power output voltage, which is referenced to the COM node.
The secondary return reference for the module's two regulated output voltages. It is dc isolated from the input
supply pins.
Using a single resistor, this pin allows V_O2 to be adjusted higher or lower than the preset value. If not used,
this pin should be left open circuit.
This is an open-collector (open-drain) positive logic input that enables the module output. This pin is
referenced to –V_I. A logic 0 at this pin disables the module's outputs, and a high impedance enables the
outputs. If not used the pin should be left unconnected.
This open-collector output may be used to enable the output of other DC/DC converters in applications where
the power-up sequence of the related voltages must be precisely controlled. The output is used principally to
control the startup up of a PTB4851xx module when powering ADSL circuits based on the AC7 chipset. The
signal is referenced to –V_I, and is active low. It is initially off (high impedance), and turns on when the output
voltage, V_O1, has risen to its nominal set-point voltage.
The signal generated by this pin is designed to be used exclusively with the PTB48510 in AC7 ADSL
applications. When the Sync Out of this converter is connected directly to the Sync In pin of the PTB48510,
both modules will operate at the same switch conversion frequency.
(POR: Available to PTB48500 and PTB48501 only.) This pin produces an active-low power-on reset signal that
may be used to reset logic circuitry. The output is set low during power up just as the output voltage from V_O1
starts to rise. It remains low for 10 ms after the voltage at V_O1 has reached its nominal set-point voltage. This
signal is referenced to the COM node, and has a 3.3-kΩ internal pull-up resistor to V_O1.
(1) Shaded functions indicate signals that are referenced to –V_I.
(2) Denotes positive logic: Open = Normal operation, –V_I = Outputs Off
(3) Denotes negative logic: High = Normal operation, Low = Reset
(4) This pin is COM on the PTB48502.
6
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