LTC3556
6
3556f
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
BUS
= 5V, V
IN1
= V
IN2
= V
IN3
= V
OUT3
= 3.8V, BAT = 3.8V, DV
CC
= 3.3V,
R
PROG
= 1k, R
CLPROG
= 3.01k, unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
FB2
V
FB2
Servo Voltage (Note 7)
l
0.780 0.800 0.820 V
R
P2
PMOS R
DS(ON)
0.6
R
N2
NMOS R
DS(ON)
0.7
R
LDO_CL2
LDO Mode Closed-Loop R
OUT
0.25
R
LDO_OL2
LDO Mode Open-Loop R
OUT
(Note 8) 2.5
I
FB2
FB2 Input Current V
FB2
= 0.85V –50 50 nA
D2 Maximum Duty Cycle
l
100 %
R
SW2
SW2 Pull-Down in Shutdown 10 k
Switching Regulator 3 (Buck-Boost)
I
VIN3
Input Current PWM Mode, I
OUT3
= 0µA
Burst Mode Operation, I
OUT3
= 0µA
Shutdown
220
13
0
400
20
1
µA
µA
µA
V
OUT3(LOW)
Minimum Regulated Output Voltage For Burst Mode Operation or Synchronous
PWM Operation
2.65 2.75 V
V
OUT3(HIGH)
Maximum Regulated Output Voltage 5.50 5.60 V
I
LIMF3
Forward Current Limit (Switch A) PWM Mode
l
2 2.5 3 A
I
PEAK3(BURST)
Forward Burst Current Limit (Switch A) Burst Mode Operation
l
200 275 350 mA
I
ZERO3(BURST)
Reverse Burst Current Limit (Switch D) Burst Mode Operation
l
–30 0 30 mA
I
MAX3(BURST)
Maximum Deliverable Output Current
in Burst Mode Operation
2.7V ≤ V
IN3
≤ 5.5V, 2.75V ≤ V
OUT3
≤ 5.5V
(Note 9)
50 mA
V
FBHIGH3
Maximum Servo Voltage Full Scale (1, 1, 1, 1)
l
0.780 0.800 0.820 V
V
FBLOW3
Minimum Servo Voltage Zero Scale (0, 0, 0, 0)
l
0.405 0.425 0.445 V
V
LSB3
V
FB3
Servo Voltage Step Size 25 mV
I
FB3
FB3 Input Current V
FB3
= 0.8V –50 50 nA
R
DS(ON)P
PMOS R
DS(ON)
Switches A, D 0.22
R
DS(ON)N
NMOS R
DS(ON)
Switches B, C 0.17
I
LEAK(P)
PMOS Switch Leakage Switches A, D –1 1 µA
I
LEAK(N)
NMOS Switch Leakage Switches B, C –1 1 µA
R
VOUT3
V
OUT3
Pull-Down in Shutdown 10 k
D
BUCK(MAX)
Maximum Buck Duty Cycle PWM Mode
l
100 %
D
BOOST(MAX)
Maximum Boost Duty Cycle PWM Mode 75 %
t
SS3
Soft-Start Time 0.5 ms
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC3556E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3: The LTC3556E includes overtemperature protection that is
intended to protect the device during momentary overload conditions.
Junction temperature will exceed 125°C when overtemperature protection
is active. Continuous operation above the specified maximum operating
junction temperature may impair device reliability.
Note 4: Total input current is the sum of quiescent current, I
VBUSQ
, and
measured current given by:
V
CLPROG
/R
CLPROG
• (h
CLPROG
+1)
Note 5: h
C/10
is expressed as a fraction of measured full charge current
with indicated PROG resistor.
Note 6: FBx above regulation such that regulator is in sleep. Specifi cation
does not include resistive divider current refl ected back to V
INx
.
Note 7: Applies to Pulse Skip, Burst Mode operation and Forced Burst
Mode operation only.
Note 8: Inductor series resistance adds to open-loop R
OUT
.
Note 9: Guaranteed by design.
