LTC3577 Datasheet, PDF (15/52 Pages) Linear Technology – Highly Integrated 6-Channel Portable PMIC

LTC3577/LTC3577-1
TYPICAL PERFORMANCE CHARACTERISTICS T_A = 25°C unless otherwise specified
DAC Code vs LED Current
70
60dB = 20mA
60
0dB = 20μA
R_{LED_FS} = 20k
50
LED Boost Start-Up Transient
I_LED
10mA/DIV
40
V_BOOST
20V/DIV
30
20
I_L
200mA/DIV
10
0
0 10 20 30 40 50 60 70
DAC CODE
3577 G43
2ms/DIV
3577 G44
LED PWM
vs Constant Current Efficiency
90
80
70
60
MAX PWM
CONSTANT
50
CURRENT
40
30
20
10
0
1.E-06
1.E-05 1.E-04 1.E-03 1.E-02 1.E-01
LED CURRENT (A)
3577 G46
Battery Discharge
vs Temperature
200
175
V_BUS = 5V
150
125
V_BUS = 0V
100
75
50 _{VBAT = 4.1V}
V_NTC < V_{TOO_HOT}
25 _{5x MODE}
I_VOUT = 0mA
0
50 60 70 80
90 100 110 120
TEMPERATURE (°C)
3577 G47
LED Boost Maximum Duty Cycle
vs Temperature
96.6
96.5
96.4
96.3
96.2
96.1
96.0
95.9
95.8
95.7
–50
3V
3.6V
4.2V
5.5V
–25 0 25 50 75
TEMPERATURE (°C)
100 125
3577 G45
Too Hot BAT Discharge
200
180
V_NTC < V_{TOO_HOT}
V_BUS = 0V
160
140
120
100
80
60
40
20
0
3.8
3.9
4.0
4.1
V_BAT (V)
4.2
3577 G48
PIN FUNCTIONS
I_LIM0, I_LIM1 (Pins 1, 2): Input Current Control Pins. I_LIM0
and I_LIM1 control the input current limit. See Table 1 in
“USB PowerPath Controller” section. Both pins are pulled
low by a weak current sink.
LED_FS (Pin 3): A resistor between this pin and ground
sets the full-scale output current of the I_LED pin.
WALL (Pin 4): Wall Adapter Present Input. Pulling this
pin above 4.3V will disconnect the power path from V_BUS
to V_OUT. The ACPR pin will also be pulled low to indicate
that a wall adapter has been detected.
SW3 (Pin 5): Power Transmission (Switch) Pin for Step-
Down Switching Regulator 3 (Buck 3).
V_IN3 (Pin 6): Power Input for Step-Down Switching Regula-
tor 3. This pin should be connected to V_OUT.
FB3 (Pin 7): Feedback Input for Step-Down Switching
Regulator 3 (Buck 3). This pin servos to a fixed voltage
of 0.8V when the control loop is complete.
OVSENSE (Pin 8): Overvoltage Protection Sense Input.
OVSENSE should be connected through a 6.2k resistor
to the input power connector and the drain of an external
3577f
15