Pin Functions - Analog Devices LINEAR LTM 8005 Manual

PIN FUNCTIONS

GND (Bank 1, Pin K1, Pin K8): Tie these GND pins to a
local ground plane below the LTM8005 and the circuit
components. In most applications, the bulk of the heat
flow out of the LTM8005 is through these pads, so the
printed circuit design has a large impact on the thermal
performance of the part. See the PCB Layout and Thermal
Considerations sections for more details. Return the feed-
back divider to this net.
SW (Bank 2): Power Switch Node. This is the drain of the
internal power switching MOSFET. For boost, buck-boost
mode and buck mode topologies, connect this bank to
the inductor and the DA bank. For a SEPIC, connect this
bank to an inductor winding and the positive coupling
capacitor terminal.
DA (Bank 3): Power Diode Anode. For boost, buck-boost
mode and buck mode topologies, connect this bank to
the inductor and the SW bank. For a SEPIC, connect this
bank to an inductor winding and the negative coupling
capacitor terminal.
V (Bank 4): Power Output Pins. Apply the output filter
OUT
capacitor between these pins and the GND pins.
ISN (Bank 5): Output Current Sense Resistor. The
LTM8005 incorporates a sense resistor between V
and ISN to set the output current regulation point and
for output current monitoring. If a larger output current
is required, apply an external resistor between V
ISN. Keep this pin voltage within 0.3V of V
LED (Bank 6): LED Current Output. Connect the anode of
the LED string to this bank.
V (Pin F1): Input Power. The V
IN
the LTM8005's internal regulators and circuitry, and must
be bypassed with a 0.22µF (or larger) capacitor placed
close to the LTM8005.
IVINN (Pin F2): Input Sense Resistor Signal. Apply an
external sense resistor between IVINP and IVINN to set
the maximum input current and for input current moni-
toring. If this function is not required, tie both IVINP and
IVINN to V . Keep this pin voltage within 0.3V of V
IN
EN/UVLO (Pin G1): Enable and Precision UVLO. An accu-
rate 1.22V falling threshold with externally programmable
hysteresis detects when power is OK to enable switching.
OUT
and
OUT
.
OUT
pin supplies current to
IN
.
IN
For more information
Rising hysteresis is generated by the external resistor
divider, an internal 499kΩ resistor between EN/UVLO and
V and an accurate internal 3µA pull-down current. Above
IN
the threshold, EN/UVLO input bias current is sub-µA.
Below the falling threshold, a 3µA pull-down current is
enabled so the user can optimize the hysteresis with the
external resistor selection. An undervoltage condition
resets soft-start. The EN/UVLO pin may be connected
directly to V , but do not drive this pin directly from
IN
another low impedance voltage source. If EN/UVLO must
be driven from a voltage source, do so with at least a 50Ω
series resistor.
IVINP (Pin G2): Input Sense Resistor Signal. Apply an
external sense resistor between IVINP and IVINN to set
the maximum input current and for input current moni-
toring. If this function is not required, tie both IVINP and
IVINN to V . Keep this pin voltage within 0.3V of V
IN
OVLO (Pin H1): Input Overvoltage Lockout Pin. An
accurate 1.25V rising threshold detects when power is
OK to enable switching. If not used, tie this pin to GND.
IVINCOMP (Pin H2): Input Current Sense Amplifier Output
Pin. The voltage at IVINCOMP pin is proportional to I
V = I • R
IVINCOMP IN INSNS
is provided internally at this pin to compensate the input
current loop. Do not load this pin with a current and do not
drive this pin with an external source, although additional
capacitance may be added externally.
SHORTLED (Pin H7): An open-collector pull-down on
SHORTLED asserts when any of the following conditions
happen:
1. FB < 0.3V after SS pin reaches 1.7V at start-up.
2. LED overcurrent (I
LED
To function, the pin requires an external pull-up resistor.
SHORTLED status is only updated during PWM high state
and latched during PWM low state. SHORTLED remains
asserted until the SS pin is discharged below 0.2V. If not
used, leave floating or tie to GND.
OPENLED (Pin H8): Fault Indicator. An open-collector
pull-down on OPENLED asserts if the FB input is above
1.20V (typical), and the LED current is less than 0.16A
(typical). To function, the pin requires an external pull-up
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LTM8005
• 20. A 10nF capacitor to GND
> 2.4A).
.
IN
as
IN
Rev. B
7