Datasheet

1.2 Performance Specification
1.3 WLED U1 Section
1.3.1 Additional WLED Section Options
1.3.2 Modifications to 3.3-V Regulator Section, U2
Introduction www.ti.com
Table 1 provides a summary of the TPS62110EVM-346 performance specifications. All specifications are
given for an ambient temperature of 25 ° C.
Table 1. Performance Specification Summary
Specification Test Conditions Min Typ Max Unit
U1 Input Voltage 5 17 V
U1 WLED Current 450 500 550 mA
U1 Low Battery Output (LBO) 8.5 V
U2 Input Voltage 5 17 V
U2 Output Voltage Iout = 10 mA to 1500 mA 3.267 3.3 3.333 V
U2 Output Current 0 1500 mA
U2 LBO VIN 8.5 V
U2 Power Good (PG) VOUT 3.25 V
The upper EVM section with integrated circuit (IC) U1 is configured as a WLED driver. The TPS62110
regulates the current through the OSRAM Golden DRAGON™ WLED at 500 mA from an input voltage
range of 5 V to 17 V. To reduce power dissipation on the current sense resistor, an external voltage
reference is used to sum a higher voltage into the FB node reducing sense voltage, V
sense
from 1.153 mV
to 255 mV.
This summing network combined with the control topology reduces the current regulator's accuracy. This
can be seen following a load transient as a change in the current regulation point. The EVM with a V
sense
voltage of 255 mV varies approximately 10%. But as V
sense
voltage increases, accuracy improves, 500 mV
will be about 5% and 1 V about 2%.
The TPS62110 can supply a wide range of current from 100 mA to 1500 mA by adjusting the sense
resistor, R10, or the reference voltage network, R1 and R2.
The equations for calculating WLED current appear in Section 3 .
The U1 circuit has the option to drive an external LED through connector J2. Onboard LED D4 must be
disconnected by removing 0- Ω resistor R22.
Driving multiple external series LEDs is possible providing that Vout is less than the Vin stepdown or buck
converter configuration. If this is done, verify that output capacitors C4 and C5 have a high enough voltage
rating. Output capacitor positions C12 and C13 are available for additional capacitors, if needed.
Additional Heat Sinking: If it is necessary to reduce operating temperature of the LED, a heat sink can
be added to the backside of the circuit board. Several types of heat sinks work in this application with the
appropriate double-sided thermal adhesive. One such heat sink is the Fischer Elecktronik SK477 which is
a 23-mm wide, 6-mm tall, and 50-mm long standard extruded heat sink.
Optional LED Lens: To focus the LED in a tighter beam, lens are available that mount on the board, such
as the Titanum-SS from Ledil or OPGD-1-002 from Dialight.
The U2 is configured for evaluation of the adjustable output version. This unit is set to 3.3 V by R18
and R4. Resistors R18 and R4 can be changed to reset the output voltage between 1.2 V and 16 V;
see the TPS62110 data sheet (SLVS585 ) for recommended values. If the output voltage is increased,
verify that the output capacitors C7 and C6 voltage rating is appropriate. Also, two extra output
capacitor positions are available if needed, C14 and C15.
2 TPS62110EVM-346 SLVU254 – September 2008
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