LTC3455EUF#TRPBF Linear Technology, LTC3455EUF#TRPBF Datasheet - Page 7

• Manufacturer Part Number: LTC3455EUF#TRPBF
• Description: IC CONV DC/DC DUAL USBBATT 24QFN
• Manufacturer: Linear Technology

Specifications of LTC3455EUF#TRPBF

• Applications: Handheld/Mobile Devices
• Voltage - Supply: 3 V ~ 6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -

PIN FUNCTIONS
FB1 (Pin 1): Feedback Pin for Switcher 1. Set the output
voltage by connecting feedback resistors to this pin.
PROG (Pin 2): Charge Current Program and Charge Cur-
rent Monitor Pin. Connect a resistor, R
to ground to program battery charge current.
In all modes the voltage on the PROG pin can be used to
measure charge current. PROG has a weak pull-up current
source to turn the charger off if the pin is left open.
TIMER (Pin 3): Timer Capacitor Pin. Connect a capacitor,
C
cycle termination time. The timer starts when USB or wall
power is fi rst present. The timer period is:
Tie TIMER to ground to disable just the internal timer
function. Tie TIMER to V
stant-current-only mode (which disables the timer, voltage
amplifi er and trickle charge function).
CHRG (Pin 4): Open-Drain Charge Status Pin. This pin is
pulled low with an internal N-channel MOSFET whenever
the battery charger is enabled, and is forced into a high
impedance state whenever it is disabled.
USBHP (Pin 5): USB High Power Mode Pin. This pin is
used to select the appropriate USB current limit (either
500mA or 100mA). Pull high to select 500mA (high power
mode); low to select 100mA (low power mode).
SUSPEND (Pin 6): USB Suspend Pin. When this pin is
pulled high, the internal USB power controller is disabled
and the USB pin current reduces to less than 20μA.
SW1 (Pin 7): Switch Pin for Switcher 1. Minimize the length
of the metal trace connected to this pin. Place the inductor
for Switcher 1 as close to this pin as possible.
USB (Pin 8): USB Supply Pin. Input current into this pin
is limited to either 100mA or 500mA based on the state
of the USBHP pin. The charger and Switcher 1 will remain
alive whenever USB power is present (when USB pin is
above 3.9V and SUSPEND is low).
V
capacitor as close to the device as possible.
TIMER
BAT
I
T
BAT
TIMER
(Pin 9): Battery Input Pin. Bypass this pin with a
, between this pin and ground to set the charge
= 1000 • 1.23V / R
(hours) = C
TIMER
MAX
PROG
• (3 hours) / (0.1μF)
to use the charger in a con-
PROG
, from this pin
V
power the two internal step-down DC/DC converters and
is provided externally to power other devices (i.e. LDOs
or Switchers for LCD bias, white LED backlight drive, etc).
When the LTC3455/LTC3455-1 is on and neither USB or
wall power are available, an internal PMOS switch connects
this pin to the V
is present, they provide power to this pin, and the battery
charger draws power from this pin. In shutdown, this pin
is discharged to ground to provide output disconnect.
WALLFB (Pin 11): Wall Power Detection Pin. This pin is the
input to a comparator used to signal the presence of a 5V
wall adapter. A resistor divider taken from the wall adapter
input is connected to this pin to tell the LTC3455/LTC3455-1
when the adapter voltage is high enough to provide power
to the LTC3455/LTC3455-1. When this pin is higher than
1.23V, the battery charger is enabled. The 5V wall adapter
is connected to the V
Tie WALLFB to ground if a wall adapter is not used.
SW2 (Pin 12): Switch Pin for Switcher 2. Minimize the
length of the metal trace connected to this pin. Place the
inductor for Switcher 2 as close to this pin as possible.
HSI (Pin 13): Hot Swap Input Pin. This pin is connected
to the HSO pin through a current-limited PMOS switch.
HSO (Pin 14): Hot Swap Output Pin. This output is used
for memory cards or other devices that would appear as
a short if they were hot-plugged directly to one of the
outputs (typically the 3.3V output). The current out of this
pin is limited to 160mA.
HSON (Pin 15): Hot Swap Enable Pin. This pin turns on
the PMOS that connects the HSI and HSO pins.
AI (Pin 16): Gain Block Input Pin. This pin is the inverting
input to an amplifi er that can be used as a low-battery
detector or as an LDO with the addition of an external
PNP or PMOS. The non-inverting input of the gain block
is connected to the 0.8V internal reference.
AO (Pin 17): Gain Block Output Pin. This pin is an open-
drain output, and is pulled low when the AI pin is less
than 800mV. This output can be used as a low-battery
detector, or as an LDO with the addition of an external
PNP or PMOS. This pin can sink up to 1mA.
MAX
(Pin 10): Max Voltage Pin. This pin is used to
BAT
LTC3455/LTC3455-1
pin. When either USB or wall power
MAX
pin through a Schottky diode.
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