LT1571 Series
Constant-Current/
Constant-Voltage Battery Chargers
with Preset Voltage and Termination Flag
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
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Fast Charging of Li-Ion, NiMH and NiCd Batteries
Simple Charge Current Programming Requires
Only One Low Cost, 1/32W Resistor
High Efficiency Charger with Up to
1.5A Charge Current
Precision 0.6% Internal Voltage Reference
Preset Battery Voltages: 4.1V, 4.2V, 8.2V, 8.4V
500kHz or 200kHz Switching Frequency
Minimizes Charger Size
Low Reverse Battery Drain Current: 5µA
Flag Indicates Li-Ion Charge Completion
5% Typical Charge Current Accuracy
Low Shutdown Current
LT1571-1: 200kHz, Adjustable Voltage
LT1571-2: 200kHz, Fixed 8.2V or 8.4V
LT1571-5: 500kHz, Fixed 4.1V or 4.2V
The LT
®
1571 PWM battery charger is a simple, efficient
solution to fast-charge rechargeable batteries including
lithium-ion (Li-Ion), nickel-metal-hydride (NiMH) and
nickel-cadmium (NiCd) using constant-current and/or
constant-voltage control. The internal switch is capable
of delivering 1.5A DC current (2A peak current). The
onboard current sense resistor (0.1Ω) allows simple
charge current programming to within 5% accuracy
using a low cost external resistor. The constant-voltage
output can be selected for 4.1V or 4.2V per cell with 0.6%
accuracy.
LT1571 can charge batteries ranging from 1V to 20V. A
saturating switch operating at 200kHz (LT1571-1,
LT1571-2) or 500kHz (LT1571-5) gives high efficiency
and small charger size. A logic output (flag) indicates
Li-Ion near full charge when the charge current drops to
20% of the programmed value. The LT1571-1 and
LT1571-2 are in a 28-pin fused lead narrow SSOP power
package. The LT1571-5 is in a 16-pin fused lead narrow
SSOP power package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
Cellular Phones, PDAs, Notebook Computers,
Portable Instruments
Cradle Chargers for Li-Ion, NiCd, NiMH and
Lead-Acid Rechargeable Batteries
TYPICAL APPLICATION
V
IN
8.2V TO 20V
(ADAPTER
OUTPUT)
D3
MBRM120T3
V
CC
C
IN
*
10µF
100k
6.19k
CHARGE
COMPLETE
4.2V
Li-Ion
BATTERY
LT1571-5
PROG
1µF
300Ω
1k
FLAG
BAT
C
OUT
***
22µF
BAT2
0.33µF
V
C
SENSE
CAP
SELECT
GND
0.1µF
BOOST
D2
MMBD914L
SW
C1
0.22µF
L1**
10µH
D1
MBRM120T3
+
+
*TOKIN OR MARCON CERAMIC SURFACE MOUNT
**COILTRONICS TP3-100, 10µH, 2.2mm HEIGHT (0.8A CHARGING CURRENT)
COILTRONICS TP1 SERIES, 10µH, 1.8mm HEIGHT (<0.5A CHARGING CURRENT)
***PANASONIC EEFCD1B220
Figure 1. Compact Li-Ion Cellular Phone Charger (0.8A)
U
1571 F01
U
U
1
LT1571 Series
ABSOLUTE
AXI U
RATI GS
Supply Voltage (V
CC
) .............................................. 28V
BOOST Pin Voltage with Respect to V
CC
................. 20V
FLAG Pin Voltage ..................................................... V
CC
I
BAT
(Average)........................................................ 1.5A
Switch Current (Peak) .............................................. 2A
Storage Temperature Range ................. – 65°C to 150°C
PACKAGE/ORDER I FOR ATIO
**GND
**GND
TOP VIEW
**GND 1
SW 2
BOOST 3
BAT2 4
FLAG 5
SELECT 6
SENSE 7
**GND 8
16 GND**
15 V
CC1
*
14 V
CC2
*
13 CAP
12 PROG
11 V
C
10 BAT
9 GND**
1
2
3
4
5
6
7
8
9
**GND
SW
BOOST
NC
FLAG
NC
V
FB
SENSE 10
**GND 11
**GND 12
**GND 13
**GND 14
GN PACKAGE
16-LEAD NARROW PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 75°C/ W
* V
CC1
AND V
CC2
SHOULD BE CONNECTED
TOGETHER CLOSE TO THE PINS
** FOUR CORNER PINS ARE FUSED TO
INTERNAL DIE ATTACH PADDLE FOR
HEAT SINKING. CONNECT THESE FOUR
PINS TO EXPANDED PC LANDS FOR
PROPER HEAT SINKING
GN PACKAGE
28-LEAD NARROW PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 40°C/ W
* V
CC1
AND V
CC2
SHOULD BE CONNECTED TOGETHER
CLOSE TO THE PINS
** ALL GND PINS ARE FUSED TO INTERNAL DIE ATTACH
PADDLE FOR HEAT SINKING. CONNECT THESE PINS TO
EXPANDED PC LANDS FOR PROPER HEAT SINKING
40°C/W THERMAL RESISTANCE ASSUMES AN INTERNAL
GROUND PLANE DOUBLING AS A HEAT SPREADER
ORDER PART NUMBER
LT1571EGN-5
Consult factory for Industrial and Military grade parts.
ORDER PART NUMBER
LT1571EGN-1
2
U
U
W
W W
U
W
(Note 1)
Operating Ambient
Temperature Range (Note 2) .................. – 40°C to 85°C
Operating Junction
Temperature Range .............................. – 40°C to 125°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
28 GND**
27 GND**
26 GND**
25 GND**
24 V
CC1
*
23 V
CC2
*
22 CAP
21 PROG
20 V
C
19 BAT
18 GND**
17 GND**
16 GND**
15 GND**
**GND
**GND
**GND
SW
BOOST
BAT2
FLAG
NC
SELECT
1
2
3
4
5
6
7
8
9
TOP VIEW
28 GND**
27 GND**
26 GND**
25 GND**
24 V
CC1
*
23 V
CC2
*
22 CAP
21 PROG
20 V
C
19 BAT
18 GND**
17 GND**
16 GND**
15 GND**
SENSE 10
**GND 11
**GND 12
**GND 13
**GND 14
GN PACKAGE
28-LEAD NARROW PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 40°C/ W
* V
CC1
AND V
CC2
SHOULD BE CONNECTED TOGETHER
CLOSE TO THE PINS
** ALL GND PINS ARE FUSED TO INTERNAL DIE ATTACH
PADDLE FOR HEAT SINKING. CONNECT THESE PINS TO
EXPANDED PC LANDS FOR PROPER HEAT SINKING
40°C/W THERMAL RESISTANCE ASSUMES AN INTERNAL
GROUND PLANE DOUBLING AS A HEAT SPREADER
ORDER PART NUMBER
LT1571EGN-2
LT1571 Series
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
V
CC
= 16V (LT1571-1, LT1571-2), V
CC
= 10V (LT1571-5), V
BAT
= 8V (LT1571-1,LT1571-2), V
BAT
= 4V (LT1571-5), no load on any
outputs unless otherwise noted. (Note 6)
PARAMETER
Overall
Supply Current
DC Battery Charging Current, I
BAT
V
PROG
= 2.7V
8V
≤
V
CC
≤
26V, 0V
≤
V
BAT
≤
20V (LT1571-1)
R
PROG
= 4.93k
R
PROG
= 4.93k, T
J
< 0°C
R
PROG
= 3.28k
R
PROG
= 49.3k
R
PROG
= 49.3k, T
J
< 0°C
V
BAT
≤
20V, 0°C
≤
T
J
≤
70°C (LT1571-1)
40
V
C
≤
40mV
R
PROG
= 4.93k. Measured at V
FB
, with VA
Supplying I
PROG
and Switch Off
8V
≤
V
CC
≤
26V, 0°C
≤
T
J
≤
70°C
8V
≤
V
CC
≤
26V, 0°C
≤
T
J
≤
125°C
8V
≤
V
CC
≤
26V, T
J
< 0°C (Note 5)
R
PROG
= 4.93k. Measured at BAT2 Pin
T
J
= 25°C
8V
≤
V
CC
≤
26V, 0°C
≤
T
J
≤
125°C
Absolute Value, Not Matching
V
BAT2
= V
PRESET
– 1V
R
PROG
= 4.93k
R
PROG
= 4.93k, R
CAP
= 65.6k
Low-to-High Threshold
High-to-Low Threshold
V
CAP
= 4.5V, I
FLAG
≤
1mA
V
CAP
= 0.6V, V
CC
= 26V
Output Current from 100µA to 500µA
V
PROG
= V
REF
, V
FB
= V
REF
+ 10mV
At 0.75mA Output Current
Undervoltage Lockout
V
CC
– V
BOOST
≤
20V
20V < V
CC
– V
BOOST
≤
26V
2V
≤
V
BOOST
– V
CC
≤
8V (Switch ON)
8V < V
BOOST
– V
CC
≤
20V (Switch ON) (LT1571-1)
q
q
q
q
q
q
q
CONDITIONS
MIN
TYP
5.2
MAX
7
1.07
1.09
1.65
125
130
15
UNITS
mA
A
A
A
mA
mA
µA
mV
0.93
0.91
1.35
75
70
1.0
1.5
100
Shutdown
Auto Shutdown, Reverse Current from Battery
(When Adapter in Figure 1 Circuit is Removed)
Shutdown Threshold at V
C
Pin
When V
CC
is Connected
Shutdown Supply Current
Reference
Reference Voltage (LT1571-1)
5
80
0.15
0.3
mA
2.446
2.441
2.430
2.465
2.465
2.465
2.480
2.489
2.480
V
V
V
Preset Battery Voltage
LT1571-2: 8.2V/8.4V
LT1571-5: 4.1V/4.2V
Voltage Setting Resistors Tolerance (R4, R5)
BAT2 Pin Input Current (LT1571-2, LT1571-5)
Charge Completion Flag (Comparator E6)
Charge Completion Threshold (Note 8)
Threshold on CAP Pin
FLAG (Open Collector) Output Low
FLAG Pin Leakage Current
Voltage Amplifier VA
Transconductance
Output Source Current
V
FB
Input Bias Current (LT1571-1)
Overall
Minimum Input Operating Voltage
Boost Pin Current
q
q
q
q
q
0.5
–1
–40
1
40
6
0.14
0.05
0.6
0.3
3
0.3
1.3
±3
6.2
7
0.10
0.25
6
8
±15
7.8
20
30
11
14
0.6
2.5
0.20
0.085
4
0.28
0.13
4.5
%
%
%
µA
A
A
V
V
V
µA
mho
mA
nA
V
µA
µA
mA
mA
3
LT1571 Series
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
V
CC
= 16V (LT1571-1, LT1571-2), V
CC
= 10V (LT1571-5), V
BAT
= 8V (LT1571-1,LT1571-2), V
BAT
= 4V (LT1571-5), no load on any
outputs unless otherwise noted. (Note 6)
PARAMETER
Switch
Switch ON Resistance
∆I
BOOST
/∆I
SW
During Switch ON
Switch OFF Leakage Current
Maximum V
BAT
with Switch ON
Minimum I
PROG
for Switch ON
Minimum I
PROG
for Switch OFF
Current Sense Amplifier Inputs (SENSE, BAT)
Sense Resistance (R
S1
)
Total Resistance from SENSE to BAT (Note 3)
BAT Bias Current (Note 4)
V
C
< 0.3V
V
C
> 0.6V
V
C
< 40mV
LT1571-1, LT1571-2
LT1571-5
All Conditions of V
CC
, Temperature,
LT1571-1, LT1571-2
LT1571-1, LT1571-2, T
J
< 0°C
LT1571-5
LT1571-5, T
J
< 0°C
LT1571-1, LT1571-2
LT1571-1, LT1571-2, T
A
= 25°C (Note 7)
LT1571-5
V
C
= 1V, I
VC
=
±1µA
q
q
q
q
q
q
q
CONDITIONS
I
SW
= 1.5A, V
BOOST
– V
SW
≥
2V
I
SW
= 1A, V
BOOST
– V
SW
< 2V (Unboosted)
V
BOOST
= (V
CC
+ 8V), I
SW
≤
1A
V
SW
= 0V, V
CC
≤
20V
V
SW
= 0V, 20V < V
CC
≤
26V
q
q
q
MIN
TYP
0.3
20
2
4
MAX
0.5
2.0
35
100
200
V
CC
– 2
27
UNITS
Ω
Ω
mA/A
µA
µA
V
µA
mA
1
1
4
2.4
0.08
0.2
– 200
700
0.12
0.25
– 375
1300
5
220
550
230
230
575
575
Ω
Ω
µA
µA
µA
kHz
kHz
kHz
kHz
kHz
kHz
%
%
%
Oscillator
Switching Frequency
Switching Frequency Tolerance
180
440
170
160
425
400
87
90
77
125
200
500
200
500
Maximum Duty Cycle
93
81
210
550
0.6
100
3
300
Current Amplifier (CA2)
Transconductance
Maximum V
C
for Switch OFF
I
VC
Current (Out of Pin)
V
C
≥
0.6V
0.2V < V
C
< 0.45V
V
C
< 40mV (Shutdown)
µmho
V
µA
mA
µA
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LT1571 is guaranteed to meet performance specifications
from 0°C to 70°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:
Sense resistor R
S1
and package bond wires.
Note 4:
Current (≈ 700µA) flows into the pins during normal operation and
also when an external shutdown signal on the V
C
pin is greater than 0.3V.
Current decreases to
≈
200µA and flows out of the pins when external
shutdown holds the V
C
pin below 0.3V but above shutdown threshold.
Current drops to near zero when input voltage collapses. See External
Shutdown in Applications Information section.
Note 5:
A linear interpolation can be used for reference voltage
specification between 0°C and – 40°C.
Note 6:
Maximum allowable ambient temperature may be limited by power
dissipation. Parts may not necessarily be operated simultaneously at
maximum power dissipation and maximum ambient temperature.
Temperature rise calculations must be done as shown in the Applications
Information section to ensure that maximum junction temperature does
not exceed the 125°C limit. With high power dissipation, maximum
ambient temperature may be less than 70°C.
Note 7:
91% maximum duty cycle is guaranteed by design if V
BAT
or V
X
(see Figure 8 in Application Information) is kept between 3V and 5V.
Note 8:
See “Lithium-Ion Charging Completion” in the Applications
Information section.
4
LT1571 Series
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency of Figure 4 Circuit
100
98
96
94
EFFICIENCY (%)
REFERENCE VOLTAGE (V)
V
CC
= 15V (EXCLUDING DISSIPATION
ON INPUT DIODE D3)
V
BAT
= 8.4V
2.466
2.464
2.462
2.460
2.458
BOOST CURRENT (mA)
92
90
88
86
84
82
80
0.1
0.3
0.5
0.7 0.9
I
BAT
(A)
1.1
1.3
1.5
Switching Frequency vs
Temperature
510
505
500
FREQUENCY (kHz)
LT1571-5
∆V
OVP
(mV)
∆V
REF
(V)
495
205
LT1571-1, LT1571-2
200
195
190
–20
–0.003
0
20 40 60 80 100 120 140
JUNCTION TEMPERATURE (°C)
1571 G04
Maximum Duty Cycle
98
97
96
LT1571-1, LT1571-2
(V
X
= 5V)
–1.20
–1.08
–0.96
–0.84
–0.60
–0.48
–0.36
–0.24
–0.12
91
90
0
20
120
JUNCTION TEMPERATURE (°C)
40
60
80
100
140
0
0.12
DUTY CYCLE (%)
I
PROG
(mA)
95
I
VC
(mA)
94
93
92
U W
1571 G01
1571 G09
Reference Voltage vs Junction
Temperature
2.470
2.468
Boost Current vs Switch Current
40
35
30
25
20
15
10
5
V
BOOST
= 21V
(V
X
= 5V)
V
CC
= 16V
V
BOOST
= 26V
(V
X
= 10V)
0
125
50
75
100
25
JUNCTION TEMPERATURE (°C)
150
0
0
0.2
0.4 0.6 0.8 1.0 1.2
SWITCH CURRENT (A)
1.4 1.6
1571 G03
1571 G02
V
REF
Line Regulation
0.003
0.002
3
4
∆V
OVP
vs I
VA
(Voltage Amplifier)
0.001
0
ALL TEMPERATURES
2
125°C
1
–0.001
–0.002
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
I
VA
(mA)
1571 G06
25°C
0
5
10
15
V
CC
(V)
20
25
30
1571 G05
V
C
Pin Characteristic
6
PROG Pin Characteristic
125°C
25°C
–0.72
0
–6
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
V
C
(V)
1571 G08
0
1
2
3
V
PROG
(V)
4
5
1571 G09
5
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