Connecting to the LM3248 Evaluation Module
7
Connecting to the LM3248 Evaluation Module
NOTE:
All of the control signals (BOOST_GATE (“BG”), MODE, ENABLE (“EN”) and VCON) can be
accessed on the bank of test access points just above connector P1, as shown in
.
The pins next to each of the silkscreened signal names are all grounded, with the exception
of the one labeled “VCON_S.” The pins with silkscreened dots indicate the active signal pins.
1. LM3248 EVM Jumper Settings
•
The LBST, L BUCK & ACB 0.1” center slide-on jumpers located on the back side of the LM3248
Evaluation Board must be installed for proper operation. See
for locations on back side of
EVM.
•
The OUT_BST shunt on the top side of the LM3248 Evaluation Board adjacent to the
BOOST_OUT banana jack is not required for normal operation, but must be in place if this banana
jack is used for monitoring the Boost Output voltage.
2. Connect the EN pin signal source with the signal source set to 0V.
3. Connect the VBATT supply to the red (+) and black (ground) banana connector pins on the left side of
the module.
4. Connect the other control signals (BOOST_GATE, MODE, and VCON) to the evaluation module,
making sure the signal sources are first set to 0V.
NOTE:
BOOST_GATE is a logic level signal (see the
) which represents the TTI
frame interval. A pulse or function generator should be used to drive this pin, but should be
configured to drive a high impedance load so that the level seen on the instrument panel is
the same as that measured into a high-Z load (50
Ω
mode will put out 2X the indicated
voltage when driving a high-Z load). Set the period to 2G=4.616 ms, 3G=10 ms or 4G=1 ms,
and the pulse width to 45 µs, to emulate the corresponding intervals that the boost "bias"
circuits need to run in these respective modes.
5. Connect the load (resistor, electronic load , or PA module) to the BUCK_OUT red (+) and GND_BUCK
black (ground) banana jacks.
8
Turn-on Sequencing
1. After insuring that ENABLE, BOOST_GATE and MODE pins are all at 0V, turn VBATT ON, and then
turn ON the ENABLE, BOOST_GATE and MODE signals (MODE=LOW for 3G/4G, HIGH for 2G). For
best accuracy, measure VBATT across the "PVIN BST" test points on the bottom of the EVM.
2. Turn on and adjust VCON to obtain the desired BUCK OUT voltage level (VCON = VOUT/2.5), which,
for best accuracy, is measured across the "BK OUT" test points on the bottom side of the EVM.
5
SNAA196 – September 2013
LM3248 2.7MHz, 2.5A Boost-Buck DC/DC Converter Evaluation Module
Copyright © 2013, Texas Instruments Incorporated