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Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357
Control of Lithium Ion Batteries (switching regulator secondary) (two cells)
Monolithic IC MM1357
Outline
This IC is used to control two-cell chargers and the secondary side of switching regulators; it features
enhanced functions for current switching and for overcharge detection and other kinds of protection. The
control output is capable of driving a photocoupler LED. The charging current can be switched between high
and low currents, and each can also be varied externally.
Features
1. Charging voltage : Can be set externally
2. Charging current (switchable between high and low levels, variable) High : 320mV typ.
Low : 145mV typ.
3. Reference voltage : 1.207V typ.
Package
SOP-14B
Applications
1. Switching regulator
2. AC adapter
3. Lithium ion battery charger
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SIP-14B
13 62457
14 11 913 12 10 8
Block Diagram
Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357
Pin Assignment
1 OUT 8 CC OUT
2 CFB 9 S
3 CSR 10 VFB+
4 CC IN 11 V
5 ADJ1 12 REG OUT
6 P
7 ADJ2 14 VFB
-
GND 13 VREF
-
GND
CC
-
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Pin Description
Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357
Pin no. Pin name
Input/output
1 OUT Output
2 CFB Input
3 CSR Input
4 CC IN Input
5 ADJ1 Input
6 P-GND Input
7 ADJ2 Input
8 CC OUT Output
9 S-GND Input
10 VFB+ Input
Function
Output pin for charging control
An external photocoupler is controlled for constant-current, constant-voltage charging control.
Amp inverting input pin for current control
An external capacitor (approx. 0.1 µF) is connected between CFB and OUT, and
phase compensation used to improve oscillation.
Current detection pin
Current is detected via the voltage drop across an external resistance between
CSR and GND (R1), to control the charging current.
Charging current switching signal input pin
CC) is the charging current 0.15V/R1, and L (GND) is the charging current
H (V
0.32V/R1. If for instance R1 is 0.1Ω, then switching is between 1.5A and 3.2A (typ.).
The switching voltage VTH is as follows.
When REG OUT is 2.5V, V
When REG OUT is 4V, V
When REG OUT is 5V, V
Amp non-inverting input pin 1 for current control
The pin voltage is set at 0.15V typ. With CC-IN at H or open, the non-inverting input
pin of the current control amp is at 0.15 V.
By adjusting the pin voltage using an external resistance or by other means, the
charging current can be varied.
Power ground pin
Amp non-inverting input pin 2 for current control
The pin voltage is set at 0.32V typ. With CC-IN at L, the non-inverting input pin of the
current control amp is at 0.32V.
By adjusting the pin voltage using an external resistance or by other means, the
charging current can be varied.
Charging current switching signal output pin
Output is in phase with CC IN. By connecting an external capacitor between CC OUT
and REG OUT, a delay can be added only when the current switching CC IN goes
from H to L. For instance, when REG OUT is 4V, on connecting an 0.1µF capacitor
CC OUT becomes about 50mS (an example is shown in the Timing Chart section).
Signal ground pin
Amp non-inverting input pin for voltage control
The charging voltage is set through the resistances at the VFB + pin and the VFB
TH is 2.05V typ.
TH is 3.0V typ.
TH is 3.7V typ.
-
pin.
11 VCC Input
12 REG OUT Output
13 VREF Input
14 VFB
-
Input
Power supply input pin
Reference voltage circuit output pin
The reference voltage can be set between 2 and 6V. The input current to start the
reference voltage should be set to 1mA or greater.
Reference voltage circuit input pin
The VREF pin voltage is set at 1.2V typ. The REG OUT voltage can be set through the
resistances between REG OUT and VREF, and between VREF and GND.
Amp inverter input pin for voltage control
Amp inverting input pin for voltage control
The charging voltage can be set through the resistances at the VFB + pin and VFB
By connecting an external capacitor (approx. 0.1µF) between VFB and OUT for phase
compensation, oscillation can be improved.
Absolute Maximun Ratings
Item Symbol Ratings Units
Storage temperature T
Operating temperature T
Power supply voltage V
Allowable loss P
STG
OPR
CC max.
D 350 mW
-
40~+125 °C
-
20~+85 °C
-
0.3~+24 V
-
pin.
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8.4V
4V
0.15V
CC IN
Low-current
mode
High-current
mode
CC OUT
V
TH VTH
0.32V
0
V
TH level
0
CC-IN
CC-OUT
CSR
V
TH level
TD
Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357
Recommended Operating Conditions
Item Symbol Ratings Units
Operating temperature T
Operating voltage V
The minimum operating voltage is under constant-current control
*
OPR
OPR +2~+20
-
15~+80 °C
*
V
Electrical Characteristics
(Except where noted otherwise, Ta=25°C, REG OUT=4V, VCC=8.4V)
Item Symbol Measurement conditions Min. Typ. Max. Units
CC minimum input current ICC Excluding REG OUT input current 0.25 0.40 mA
V
Amp input for voltage control
Input offset voltage V
Input bias current VFB+ I
Input bias current VFB
-
Common-mode input voltage range V
IO 15mV
B+ 20 250 nA
IB
-
I
*
20 250 nA
0.7
REG OUT
-
0.7
Amp input for current control
ADJ1 pin input impedance R
ADJ2 pin input impedance R
CFB pin input impedance R
Current limit 1 V
Current limit 2 V
OUT pin input current 1 I
OUT pin input current 2 I
OUT pin leakage current I
CC IN input impedance R
CC switching voltage L (VTR mode) V
CC switching voltage H (CHG mode) V
CC OUT output intake current I
CC OUT output current I
CC OUT output voltage range V
Reference voltage V
REG OUT output voltage variable range
REG OUT maximum input current I
REG OUT minimum input current I
Because there is an internal circuit for protection against shorts of external components, the common-mode
*
input voltage range is 0.7V to REG OUT
there is a short between VBF+ and REG OUT or between VFB
ADJ113kΩ
ADJ213kΩ
CFB 2kΩ
CL1 High-current mode 310 320 330 mV
CL2 Low-current mode 137 145 153 mV
S1 OUT=8.4V (voltage-control amp) 20 mA
S2 OUT=4 V (voltage-control amp) 20 mA
L OUT=24V 2 µA
CI 100 kΩ
CL 2.6 V
CH 3.4 V
CO1
On switching from low to high current mode
CO2
On switching from high to low current mode
CO 0.4 3.6 V
REF 1.195 1.207 1.219 V
6µA
0.5 mA
VREG 2.0 6.0 V
max. 20 mA
min. 1.0 mA
-
0.7V. Values are set such that overvoltages do not occur when
-
and GND.
V
Timing Chart
Timing chart for connection of a timing capacitor CT to CC OUT
With REG OUT at 4V and C
T=0.1µF, TD is approx. 50mS.
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0.35
0.3
0.25
-
25 0 25 50 75 85
Ambient temperature (°C)
Current limit 1 (V)
0.2
0.15
0.1
-
25 0 25 50 75 85
Ambient temperature (°C)
Current limit 2 (V)
Application Circuits
Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357
Note 1 : 1. The REG OUT voltage can be set to 1.2V typ. (R5+R6)/R6. (REG OUT = 2 to 6V)
2. The value of R4 should be set according to the load. (Consider it to be a shunt regulator.)
3. The voltage under constant-voltage charging is equal to (R3/R2) REG OUT. When a highprecision voltage is required, use the knob for adjustment.
4. The current in constant-current charging can be set to either of two values, 0.15V/R1 (when CC-IN
is H), and 0.32V/R1 (when CC-IN is L).
5. R7 is a resistance for current limiting.
6. The capacitors C1 and C5 are to prevent oscillation; C4 is for soft starting of the REG OUT
voltage; and C2 is used to delay current switching (CC-OUT switched from H to L).
Note 2 : This IC incorporates a voltage-controlling amp and protection against shorting to VREF ; when R2,
R3, R5 and R6 are shorted, the voltage is limited to its minimum value. By means of a comparator
within the VFB+, VFB
-
and VREF pin area, upon resistance shorting the OUT pin is forced to L.
Note 3 : The above diagram is an example for reference purposes; in actual use the circuit should be studied
thoroughly prior to use.
Characteristics
Current limit 1 vs temperature
Current limit 2 vs temperature
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3.5
3
2.5
-
25 0 25 50 75 85
Ambient temperature (°C)
CC IN, L H
CC IN, H L
CC switching voltage (V)
5
4
3
2
1
0
23456
REG OUT voltage (V)
CC IN, L H
CC IN, H L
CC switching voltage (V)
5
4
3
2
1
0
-
1
0 20 40 60 10080 120
TIME (mS)
CT=0.1µF
CT=0.047µF
CT=0µF
CC OUT (V)
8
6
10
4
0
2
-
25 0 25 50 75 85
Ambient temperature (°C)
CC OUT intake current (µA)
5
4
3
2
1
0
0.1 1 10 100
REG OUT input current (mA)
REG OUT voltage (V)
1.22
1.21
1.2
-
25 0 25 50 75 85
Ambient temperature (°C)
Reference voltage (V)
4.05
4
3.95
-
25 0 25 50 75 85
Ambient temperature (°C)
REG OUT input current10mA
REG OUT voltage (4V) (V)
Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357
Reference voltage vs temperature
CC switching voltage vs temperature
REG OUT=4V
REG OUT voltage (4V)-temperature
CC switching voltage vs REG OUT voltage
CC OUT-DELAY TIME Ta=25°C REG OUT=4V
(CTis the capacitance between CC OUT and REG OUT)
REG OUT voltage vs REG OUT input current Ta=25
CC OUT intake current vs temperature
°C
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