Datasheet LTC4121, LTC4121-4.2 (Analog Devices) - 8

LTC4121/LTC4121-4.2
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. IN Pin Switching Current IN Pin Sleep Current IN Pin Standby Current vs Input Voltage vs Input Voltage vs Input Voltage
7 140 180 IBAT = 0 SLEEP 130°C 170 6 120 SLEEP 25°C SLEEP –45°C 160 5 FREQ = INTVCC 100 150 (mA) 4 80 140 (µA) (µA) 130 3 I IIN 60 I IIN 120 I IN(SWITCHING) 2 40 110 FREQ = GND 130°C 100 1 25°C 20 STANDBY FREQ HIGH 25°C –45°C 90 STANDBY FREQ LOW 25°C 0 0 80 5 10 15 20 25 30 35 40 5 10 15 20 25 30 35 40 5 10 15 20 25 30 35 40 VIN (V) VIN (V) VIN (V) 4121 G17 4121 G18 4121 G19
PIN FUNCTIONS INTVCC (Pin 1):
Internal Low Drop Out (LDO) Regulator
GND (Pin 5, Exposed Pad Pin 17):
Ground Pin. Connect to Output Pin. This pin is the output of an internal linear Exposed Pad. The Exposed Pad must be soldered to PCB regulator that generates the internal INTVCC supply from GND to provide a low electrical and thermal impedance IN. It also supplies power to the switch gate drivers and connection to ground. the low battery linear charge current ILOWBAT. Connect
MPPT (Pin 6):
Maximum Power Point Tracking Pin. This a 2.2µF low ESR capacitor from INTVCC to GND. Do not pin is used to program an input voltage regulation loop. place any external load on INTVCC other than the NTC bias Connect an external resistive divider from V network. Overloading this pin can disrupt internal operation. IN to MPPT to GND. This divider programs the maximum power point When the RUN pin is above VEN, and INTVCC rises above voltage as percentage of the input open-circuit voltage. the UVLO threshold and IN rises above BAT by ∆VDUVLO For more information on programming the MPPT resis- and its hysteresis, the charger is enabled. tive divider refer to the Application Information section. If
BOOST (Pin 2):
Boosted Supply Pin. Connect a 22nF boost the input voltage regulation feature is not used, connect capacitor from this pin to the SW pin. MPPT to either INTVCC or IN with a minimum 10k resistor.
IN (Pin 3):
Positive Input Power Supply. Decouple to GND Keep parasitic capacitance at the MPPT pin to a minimum with a 10µF or larger low ESR capacitor. The input supply as capacitance at this pin forms a pole that may interfere impedance and the input decoupling capacitor form an RC with switching regulator stability. network that must settle during the MPPT sample pulse
FREQ (Pin 7):
Step-Down Regulator Switching Frequency width of about 36ms. This allows the LTC4121 to sample Select Input Pin. Connect to INTVCC to select a 1.5MHz the open-circuit voltage. switching frequency or GND to select a 750kHz switching
SW (Pin 4):
Switch Pin. The SW pin delivers power from frequency. Do not float. IN to BAT via the step-down switching regulator. An in-
CHGSNS (Pin 8):
Battery Charge Current Sense Pin. An ductor should be connected from SW to CHGSNS. See internal current sense resistor between CHGSNS and BAT the Applications Information section for a discussion of pins monitors battery charge current. An inductor should inductor selection. be connected from SW to CHGSNS. 4121fc 8 For more information www.linear.com/LTC4121 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Applications Examples Package Description Typical Application Related Parts