Texas Instruments tps61040EVM-002, Руководство пользователя

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Input/Output Connections
2-2
2.1 Input/Output Connections
The TPS61040EVM−002 PWB has several connections, which are described
in Table 2−1.
Table 2−1. Input/Output Connections
Reference
Designator Name Description
J1 Vin This is the positive connection to the input power supply. Input supply leads (Vin
and GND) should be a twisted pair and kept as short as possible.
J2 GND This is the return connection for the input power supply.
J3 DIM1 Input for dimming adjust of LED current
J3 DIM2 Input for dimming adjust of LED current
J3 GND Ground connection for the dimming adjust signal
J4 LED Anode Output to anode of LED
J5 LED
Cathode Output to cathode of LED
J6 GND Ground connection
JP1 Enable Use this connector to enable and disable the power supply. Connect a jumper
between the ON pin and the center pin to enable the supply. Connect a jumper
between the OFF pin and the center pin to disable the supply. If this pin is left open,
the EVM does not operate correctly. This pin is also used for PWM dimming control
of the LED current.
2.2 EVM Operation
The EVM is configured as a constant current supply. Current regulation is
accomplished by regulating the voltage across a current sense resistor. The
EVM does not operate correctly unless a load is placed between J4 (LED
Anode) and J5 (LED Cathode). With no load, the output voltage increases until
clamped by the 27−V zener diode shown in the schematic.
The EVM provides the user with a place to add up to four LEDs (D2 through
D6). More or fewer than four LEDs may be used, but the connections to the
board must be made such that the load current flows from the LED anode
connection to the LED cathode connection. If a resistive load is being
substituted for LEDs, the load resistance must be small enough so that the
resistance times the programmed load current is less than 27 V.
This EVM is designed to accommodate several LED-dimming techniques.
Because of this flexibility, circuitry may be present on the EVM that is not
needed for the particular dimming method you choose. Depending on the
PWM dimming technique used, component values may need to be changed
to provide the desired LED current level. Before using the EVM, determine the
method of dimming. Descriptions of several dimming techniques follow.
2.2.1 Analog Dimming With Analog Voltage
One method for dimming the LEDs is to inject a voltage through a resistor into
the FB pin of the TPS61040. The injected voltage artificially raises the voltage