Datasheet

LTC4089/LTC4089-5
9
40895fc
OUT (Pin 13): Voltage Output. This pin is used to provide
controlled power to a USB device from either USB V
BUS
(IN), an external high voltage supply (HVIN), or the battery
(BAT) when no other supply is present. The high voltage
supply is prioritized over the USB V
BUS
input. OUT should
be bypassed with at least 4.7μF to GND.
CLPROG (Pin 14): Current Limit Program and Input Cur-
rent Monitor. Connecting a resistor, R
CLPROG
, to ground
programs the input to output current limit. The current
limit is programmed as follows:
IA
V
R
CL
CLPROG
()=
1000
In USB applications, the resistor R
CLPROG
should be set
to no less than 2.1k. The voltage on the CLPROG pin is
always proportional to the current fl owing through the
IN to OUT power path. This current can be calculated
as follows:
IA
V
R
IN
CLPROG
CLPROG
() •= 1000
HPWR (Pin 15): High Power Select. This logic input is used
to control the input current limit. A voltage greater than
2.3V on the pin will set the input current limit to 100% of
the current programmed by the CLPROG pin. A voltage
less than 0.3V on the pin will set the input current limit to
20% of the current programmed by the CLPROG pin. A
2μA pull-down current is internally connected to this pin
to ensure it is low at power up when the pin is not being
driven externally.
SUSP (Pin 16): Suspend Mode Input. Pulling this pin
above 2.3V will disable the power path from IN to OUT.
The supply current from IN will be reduced to comply
with the USB specifi cation for suspend mode. Both the
ability to charge the battery from HVIN and the ideal diode
function (from BAT to OUT) will remain active. Suspend
mode will reset the charge timer if V
OUT
is less than V
BAT
while in suspend mode. If V
OUT
is kept greater than V
BAT
,
such as when the high voltage input is present, the charge
timer will not be reset when the part is put in suspend.
A 2μA pull-down current is internally applied to this pin
to ensure it is low at power-up when the pin is not being
driven externally.
TIMER (Pin 17): Timer Capacitor. Placing a capacitor,
C
TIMER
, to GND sets the timer period. The timer period is:
t hours
C R hours
μF k
TIMER
TIMER PROG
()
••
.•
=
3
0 1 100
Charge time is increased if charge current is reduced
due to undervoltage current limit, load current, thermal
regulation and current limit selection (HPWR).
Shorting the TIMER pin to GND disables the battery
charging functions.
SW (Pin 19): The SW pin is the output of the internal high
voltage power switch. Connect this pin to the inductor,
catch diode and boost capacitor.
BOOST (Pin 20): The BOOST pin is used to provide a
drive voltage, higher than the input voltage, to the internal
bipolar NPN power switch.
HVIN (Pin 21): The HVIN pin supplies current to the inter-
nal high voltage regulator and to the internal high voltage
power switch. The presence of a high voltage input takes
priority over the USB V
BUS
input (i.e., when a high volt-
age input supply is detected, the USB IN to OUT path is
disconnected). This pin must be locally bypassed.
HVEN (Pin 22): The HVEN pin is used to disable the high
voltage input path. Tie to ground to disable the high voltage
input or tie to at least 2.3V to enable the high voltage path.
If this feature is not used, tie to the HVIN pin. This pin can
also be used to soft-start the high voltage regulator; see
the Applications Information section.
Exposed Pad (Pin 23): Ground. The exposed package
pad is ground and must be soldered to the PC board for
proper functionality and for maximum heat transfer (use
several vias directly under the LTC4089).
PIN FUNCTIONS