Application Note: SY6953
High Efficiency, 2-4 cell Buck Li-Ion Battery Charger
Advanced Design Specification
General Description
Features
SY6953 is a wide input, high integrated and high
efficiency Buck mode battery charger. It accepts 428V input and supports 2-4 cells Li-ion and Lipolymer battery. The charge current up to 2A can be
programmed by using the external resistor for
different portable applications. It also has a
programmable charge timeout and adaptive input
power limit for safety battery charge operation. It
consists of 30V rating reverse blocking FET and
power switching FETs with low ON resistance to
achieve high charge efficiency and simple peripheral
circuit design.
SY6953 along with small QFN3x3-18 footprint
provides small PCB area application.
Ordering Information
SY6953 □(□□)□
Temperature Code
Package Code
Optional Spec Code
Ordering Number
SY6953QIC
Package type
QFN3×3-18
Wide Input Voltage Range: 4V to 28V
Constant Voltage Selectable: 4.1V/4.2V/4.35V
per Cell
Charge Current up to 2A for 2 Cells Battery
Charge Current up to 1.6A for 3 Cells Battery
Charge Current up to 1.5A for 4 Cells Battery
Programmable VDPM
Programmable Input Current Limit
Programmable Charge Timer
Trickle Current / Constant Current / Constant
Voltage Charging Mode
Thermal Regulation
Input Voltage UVLO and OVP Protection
BAT OVP and Short Protection
Over Temperature Protection
Charging Status Indication
NTC JEITA Compliance
Package QFN3x3-18
Applications
Note
Floor Cleaning Robot
Window & Door Automation
Smart Speaker
Electrical Tools
Application Circuit
INPUT
CIN
RUP
CPMID
IN
PMID
VSEN
RDOWN
RSTAT DSTAT
IN
CBST
BST
VDD
Li-Ion
Battery
RS
STAT
BAT
VDD
CVDD
RS
LX
SY6953
EN
L
CBAT
TIM
CTIM
RNTC
GND
RILIM
ILIM
NTC
CV
CELL
High/Low/Floating
Figure1. Schematic Diagram
AN_SY6953 Rev. 0.0A
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AN_SY6953
Pinout (top view)
VSEN EN STAT TIM CELL
18
17
16
15
14
ILIM
1
13
RS
IN
2
12
BAT
PMID
3
11
CV
LX
4
10
NTC
5
6
7
8
9
PGND PGND BST VDD SGND
(QFN3x3-18)
Top Mark: CNWxyz, (Device code: CNW, x=year code, y=week code, z= lot number code)
Pin Name
Pin No
ILIM
1
IN
2
PMID
3
LX
PGND
BST
VDD
SGND
NTC
4
5,6
7
8
9
10
CV
11
BAT
RS
12
13
CELL
14
TIM
15
STAT
16
EN
17
VSEN
18
AN_SY6953 Rev. 0.0A
© 2019 Silergy Corp.
Description
Input current limit program pin. Connect a resistor from this pin to GND to program input
current limit. The mirror current about 1/3000 of the blocking FET current will dump into
the external resistor through ILIM pin and compared to the internal reverence 1V. So IINLIM
= (1V/RILIM) ×3000
Analog power input pin. Connect a MLCC from this pin to ground to decouple high
harmonic noise. This pin has OVP and UVLO function to make the charger operate within
safe input voltage area. Suggest 1uF at least on this pin to ground.
Connected to the drain of the reverse blocking NFET and HSFET. Suggest 10uF at least on
this pin to ground.
Switch node pin. Connect to external inductor.
Power ground pin.
Boot strap for high HSFET driver.
Internal LDO output. Connect this pin with 1uF capacitor to ground.
Signal ground pin.
Thermal protection pin. It will meet JEITA spec and refer to description section.
Battery CV voltage selection pin. Pull low for 4.2V/cell, pull high for 4.35V/cell and float
this pin for 4.1V/cell.
Battery positive pin.
Charge current sense resistor positive pin.
Battery cell selection pin. Different cell numbers can be selected by this pin. Float for 2
cells, pull low for 3 cells, pull high for 4 cells.
Charge time limit pin. Connect this pin with a capacitor to ground. Internal current source
charges the capacitor for TC mode and fast charge (CV&CC) mode’s charge time limit. TC
charge time limit is about 1/9 of fast charge time limit.
Charge status indication pin. It is open drain output and pulled high to IN thru a LED to
indicate the charge in process. When the charge is done, LED is off. When some fault
happens during charging, LED will flash with 2Hz frequency.
IC enable pin. Pull high to enable the IC and low to shut down the IC. Floating this pin will
also shut down the IC.
Input voltage sense pin. If the voltage drops to internal 1.2V reference voltage, the input
voltage will be clamped to the setting value.
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AN_SY6953
Block Diagram
BKFET
PMID
IN
Charge
Pump
NTC
Protection
VDD
VDD
LDO
BST
OVP/UVLO
VDD
STAT
PWM
Control
Charge Status
Judge
VSEN
HSFET
LX
LSFET
VDPM Loop
RS
Ichg
40 Times
CV Ref
Select
CV
Charge Control &
Protection Logic
Current Source
BAT
Ichg
ChargeTermination
& Recharge
TIM
CC/TC/SC
Judge
Timeout
Count
BATOVP
Thermal
Shutdown
CELL
CV Ratio
Select
BKFET IMIRROR
IN
CMP
ILIM
1/3000
JEITA
Spec
EN
GND
NTC
Figure2. Block Diagram
Absolute Maximum Ratings (Note 1)
IN, PMID, LX, BAT, VSEN, STAT, CV, CELL, EN --------------------------------------------------------- -0.3V to 33V
TIM, VDD, NTC, ILIM ----------------------------------------------------------------------------------------------- -0.3V to 4V
RS-BAT ------------------------------------------------------------------------------------------------------- ----- -0.3V to +0.3V
BST-LX ----------------------------------------------------------------------------------------------------------------- -0.3V to 4V
LX Pin Current Continuous ------------------------------------------------------------------------------------------------ 2A
Power Dissipation, PD @ TA = 25°C, QFN3x3-18 ------------------------------------------------------------------------- 1.6W
Package Thermal Resistance (Note 2)
θ JA ---------------------------------------------------------------------------------------------------------- ---------- 75°C/W
θ JC ------------------------------------------------------------------------------------------------------------------- 20°C/W
Junction Temperature Range ----------------------------------------------------------------------------- -40°C to +125°C
Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------------------- 260°C
Storage Temperature Range ------------------------------------------------------------------------------------ -65°C to 150°C
Recommended Operating Conditions (Note 3)
IN -------------------------------------------------------------------------------------------------------------------------- 4V to 28V
PMID, LX, BAT, VSEN, STAT, CV, CELL, EN ----------------------------------------------------------------- 0V to 28V
TIM, ILIM, NTC -------------------------------------------------------------------------------------------------------- 0V to 3.3V
RS-BAT ----------------------------------------------------------------------------------------------------- ---- -0.25V to +0.25V
Junction Temperature Range ------------------------------------------------------------------------------------ -40°C to 100°C
Ambient Temperature Range ------------------------------------------------------------------------------------- -40°C to 85°C
AN_SY6953 Rev. 0.0A
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AN_SY6953
Electrical Characteristics
TA=25°C, VIN=20V, GND=0V, CIN=1uF, CPMID=10uF, L=4.7uH, RS=25mΩ, CTIM=330nF, unless otherwise
specified.
Parameter
Bias Supply (VIN)
Supply Voltage Operation
Range
Input Voltage Lockout
Threshold
Input Voltage Lockout
Hysteresis
Input Over Voltage
Protection
Input Over Voltage
Protection Hysteresis
Quiescent Current
Battery Discharge Current
Input Quiescent Current
Input Shutdown Current
Oscillator and PWM
Switching Frequency
Main NFET Minimum On
Time
Main N-FET Minimum Off
Time
Power MOSFET
RDS(ON) of Main N-FET
RDS(ON) of Rectified N-FET
RDS(ON) of Blocking N-FET
Voltage Regulation
Symbol
Conditions
VIN
Min
Typ
Max
Unit
4
28
V
3.5
3.9
V
VUVLO
VIN rising and measured from
IN to PGND
∆VUVLO
Measured from IN to PGND
0.2
V
VIN_OVP
VIN rising and measured from
IN to PGND
29
V
∆VIN_OVP
Measured from IN to PGND
0.5
V
IBAT
IIN
ISD
Input absent, VBAT=17.4V
VIN=28V, EN=1, No switching
VIN=28V, EN=0
15
0.8
60
25
1.1
fSW
500
kHz
tON_MIN
100
ns
tOFF_MIN
100
ns
RHSFET
RLSFET
RBKFET
120
180
150
mΩ
mΩ
mΩ
2-cell, CV is floating
2-cell, VCV1.5V
3-cell, CV is floating
3-cell, VCV1.5V
4-cell, CV is floating
4-cell, VCV1.5V
2-cell battery
3-cell battery
4-cell battery
2-cell battery
3-cell battery
4-cell battery
8.2
8.4
8.7
12.3
12.6
13.05
16.4
16.8
17.4
200
300
400
5.6
8.4
11.2
Battery Charge Voltage
VBAT_REG
Recharge Threshold refer
to VBAT_REG
ΔVRCH
Trickle Charge Rising
Edge Threshold
VTRK
Charge Current
Charge Current Accuracy
for Constant Current Mode
ICC
ICC=30mV/RS
-4%
4%
Charge Current Accuracy
for Trickle Current Mode
ITC
ITC=3mV/RS
-25%
25%
Termination Current
ITERM
ITERM=3mV/RS
-25%
25%
AN_SY6953 Rev. 0.0A
© 2019 Silergy Corp.
uA
mA
uA
V
mV
V
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AN_SY6953
Input Current Limit
Input Current Limit Accuracy
IINLIM
IINLIM=500mA
BAT Voltage OVP
BAT OVP Threshold
VBAT_OVP
VBAT rising
BAT OVP Threshold Hysteresis ∆VBAT_OVP
VDPM Reference
Reference for VDPM
VVSEN_DPM
VDD Regulation
VDD LDO Voltage
VVDD
VIN>4V, EN=1
VDD Current Capacity
IVDD
VVDD=3V
VDD Current Limit
IVDD_LIMIT
VDD short to ground
Timer
Trickle Current Charge Timeout tTC
CTIM=330nF
Constant Current Charge
tCC
Timeout
Charge Mode Change Delay
tMC
Time
Termination Delay Time
tTERM
Recharge Time Delay
tRCHG
Cycle-by-Cycle Peak Current Limit
Power FET Current Limit
IPEAK
VBAT> VSHORT
BAT Short Protection
BAT Short Protection
VSHORT
VBAT falling
Threshold
Auto Shut Down
VIN falling, measured from
Auto Shutdown Voltage
VASD
Threshold
IN to BAT
Auto Shutdown Voltage
VIN rising hysteresis,
VASD_HYS
Threshold Hysteresis
measured from IN to BAT
Logic Control
High Level Logic for EN
VEN_H
Low Level Logic for EN
VEN_L
High Level Logic for CV,CELL VLOGIC_H
Low Level Logic for CV,CELL VLOGIC_L
NTC Thermal Protection JEITA Spec
VNTC_TI
VNTC rising
T1(0 ºC) Threshold
V
T1(0 ºC) Threshold Hysteresis
NTC_TI_HYS
VNTC_T2
VNTC rising
T2(10 ºC) Threshold
T2(10 ºC) Threshold Hysteresis VNTC_T2_HYS
VNTC_T3
VNTC falling
T3(45 ºC) Threshold
T3(45 ºC) Threshold Hysteresis VNTC_T3_HYS
VNTC_T5
VNTC falling
T5(60 ºC) Threshold
T5(60 ºC) Threshold Hysteresis VNTC_T5_HYS
Thermal Regulation and Thermal Shutdown
Junction Thermal Regulation
TJ_REG
Accuracy
Thermal Shutdown Threshold
TSD
Thermal Shutdown Threshold
TSD_HYS
Falling Edge
Hysteresis
AN_SY6953 Rev. 0.0A
© 2019 Silergy Corp.
-5%
5%
104
2
% VBAT_REG
% VBAT_REG
1.2
V
3.3
V
mA
mA
20
50
0.5
hour
4.5
hour
30
ms
30
30
ms
ms
3
A
2.00
V
200
mV
80
1.5
0.4
3
0.5
V
V
V
V
73.25
1.25
68.25
1.25
44.75
1.2
34.375
1.2
%VVDD
120
ºC
150
ºC
20
ºC
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AN_SY6953
Note 1: Stresses beyond the “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only. Functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specification is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability.
Note 2: JA is measured in the natural convection at T A = 25°C on a low effective four-layer thermal conductivity
test board of JEDEC 51-3 thermal measurement standard.
Note 3: The device is not guaranteed to function outside its operating conditions
AN_SY6953 Rev. 0.0A
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AN_SY6953
Typical Performance Characteristics
(TA=25°C, VIN=20V, CIN=1uF, CPMID=10uF, L=4.7uH, RS=25mΩ, unless otherwise specified)
Efficiency vs. Charge Current (CV Mode)
96
96
94
95
92
94
Efficiency (%)
Efficiency (%)
Efficiency vs. Charge Current (CV Mode)
90
88
2cell
3cell
86
93
92
91
Vin=12V 2cell
4cell
84
90
82
89
Vin=15V 3cell
Vin=20V 4cell
0
0.5
1
1.5
2
2.5
0
0.5
1
1.5
Charge Current (A)
Charge Current (A)
Efficiency vs. Battery Voltage (CC Mode)
Startup from EN
2
2.5
95
Efficiency (%)
94
93
VEN
92
VLX
91
VSTAT
90
2cell Icc=1.2A
3cell Icc=1.2A
4cell Icc=1.2A
2cell Icc=0.6A
3cell Icc=0.6A
4cell Icc=0.6A
89
88
87
IL
20V/div
20V/div
10V/div
1A/div
86
5
7
9
11
13
15
17
Time (20ms/div)
Battery Voltage(V)
Steady Waveform at CV Mode
Shutdown from EN
(VBAT=12.6V, ICHG=0.6A)
VEN
20V/div
VBAT
10V/div
VLX
20V/div
VLX
20V/div
VSTAT
10V/div
VSTAT
IL
10V/div
1A/div
IL
Time (20ms/div)
AN_SY6953 Rev. 0.0A
© 2019 Silergy Corp.
1A/div
Time (1µs/div)
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AN_SY6953
Steady Waveform at CC Mode
Steady Waveforms at TC Mode
(VBAT=10V, ICHG=1.2A)
(VBAT=5V)
VBAT
10V/div
VLX
20V/div
VBAT
5V/div
VSTAT
10V/div
IL
VSTAT
IL
0.5A/div
10V/div
1A/div
VLX
20V/div
Time (1µs/div)
Time (1µs/div)
Insert and Remove Adapter
Insert and Remove Battery
(CC Mode, VBAT=10V)
(CC Mode, VBAT=10V)
VIN
VLX
VSTAT
IL
20V/div
VBAT
10V/div
VNTC
2V/div
VSTAT
50V/div
IL
2A/div
20V/div
20V/div
1A/div
Time (400ms/div)
Time (1s/div)
NTC JEITA Function
NTC JEITA Function
(CV Mode, ICHG=0.6A)
(CC Mode, VBAT=10V)
VNTC
VNTC
VBAT(12V offset)
0.5V/div
1V/div
VBAT
10V/div
VSTAT
20V/div
VSTAT
50V/div
ICHG
0.5A/div
ICHG
1A/div
Time (400ms/div)
AN_SY6953 Rev. 0.0A
© 2019 Silergy Corp.
2V/div
Time (1s/div)
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AN_SY6953
Input Power Limit Principle
General Function Description
SY6953 is a 4-28V input, 2-4 cells Li-Ion
synchronous Buck charger. The charge current up to
2A can be programmed by using the external resistor
for different portable applications. It also has a
programmable charge timeout and adaptive input
power limit for safety battery charge operation. It
consists of 30V rating reverse blocking FET and
power switching FETs with low ON resistance to
achieve high charge efficiency and simple peripheral
circuit design.
SY6953 along with small QFN3x3-18 footprint
provides small PCB area application.
Switching Mode Control Strategy
SY6953 utilizes quasi-fixed frequency control to
simplify the internal close-loop compensation design.
The quasi-fixed frequency settled at 500 kHz is easy
for the size minimization of peripheral circuit design.
Operation Principle
SY6953 works as a synchronous Buck mode battery
charger when the adapter is present. It utilizes 500
kHz switching frequency to minimize the PCB design.
The charger will operate in battery short mode,
trickle charge mode, constant current charge mode
and constant voltage charge mode according to the
battery voltage. The charge current in every mode is
showed in following charge curve. In constant
voltage mode, if charge current is lower than
termination current, the charger will stop charging
until battery voltage drops to recharge voltage.
VBAT
Battery
Voltage
VTRK
t
ICHG
ICC
Charging Status Indication Description
STAT is an open drain pin and a pull up resistor is
needed for charging status indication. Connect a LED
from IN to STAT pin, LED ON means Charge-inProcess, LED OFF means Charge Done, LED
Flashing with 2Hz means Fault Mode.
1. Charge-In-Process – Pull and keep STAT pin to
Low;
2.
Charge Done – Pull and keep STAT pin to High;
3.
Fault Mode – Output high and low voltage
alternatively with 2Hz frequency. The faults
include input OVP, BAT OVP, BAT short, NTC
JEITA UTP/OTP (below T1 or above T5), Timeout and Thermal shutdown.
Full Charger Protections Description
In charge mode, SY6953 has full protections to
protect the IC and the battery.
Input Over Voltage Protection – SY6953 has IN over
voltage protection. It will stop charge when input
OVP occurs. IC will auto recover normal operation
when this fault removes.
BAT Over Voltage Protection – SY6953 will stop
charge when BAT OVP occurs. IC will auto recover
normal operation when this fault removes.
JEITA NTC Thermal Protection – When NTC
voltage is lower than VNTC_T5 threshold or higher than
VNTC_T1 threshold, the converter will stop charge. IC
will auto recover when this fault removes.
Thermal Shutdown Protection – The IC will stop
operation when the junction temperature is higher
than 150°C. It will auto recover normal when this
fault removes.
Charge
Current
ITC
ISC
0
It will automatically decrease charge current when
input current exceeds setting value or VSEN voltage
drops to internal 1.2V reference.
Timeout Protection – The charger can detect a bad
battery. It will stop charge and latch off when the
charger works over safety time which is set by CTIM.
Only recycling the input or EN signal can release this
fault.
VBAT_REG
VSHORT
0
For prevent input source overloading, SY6953 has
IDPM and VDPM loop to limit the input power.
t
Constant current
Trickle
BAT short
charge
current charge
Constant voltage
charge
Figure3. Charge Curve
AN_SY6953 Rev. 0.0A
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AN_SY6953
Charge JEITA Guideline Compliance
Cold
-20
-10
0.5ICC
Cool
T1
Normal
T2
20
30
Warm
T3
Hot
T5
70℃
Battery Temperature
VBAT_REG
VBAT_REG-150mV*cells
Charging Voltage
SY6953 can meet the JEITA requirement. The
voltage setting at warm temperature (T 3–T5) can be
150mV*cells lower than VBAT_REG. The current
setting at cool temperature (T1–T2) can be reduced to
50% of fast charge current ICC.
ICC
Charging Current
To improve the safety of charging Li-ion batteries,
JEITA recommend the voltage on NTC pin must be
within the VNTC_T1 to VNTC_T5 thresholds. If NTC
voltage exceeds the VNTC_T1–VNTC_T5 range, the
controller suspends charging and waits until the
battery temperature is within the T 1 to T5 range. At
cool temperature (T1–T2), JEITA recommends the
charge current to be reduced to at least half of the
constant charge current or lower. At warm
temperature (T3–T5), JEITA recommends charge
voltage less than 4.1V (for 4.2V CV voltage).
Cold
-20
-10
Cool
T1
Normal
T2
20
30
Warm
T3
Hot
T5
70℃
Battery Temperature
Figure4. JEITA Guideline
AN_SY6953 Rev. 0.0A
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AN_SY6953
Application Information
Because of the high integration of SY6953, the
application circuit based on this regulator IC is rather
simple. Only input capacitor CPMID, output capacitor
CBAT, inductor L, NTC resistors R1, R2, charge
current sense resistor RS and timer capacitor CTIM
need to be selected for the targeted application
specification.
NTC Resistor
SY6953 monitors battery temperature by measuring
the VDD voltage and NTC voltage. It will trigger
JEITA protection when the ratio K (K= VNTC/VVDD)
reaches the related threshold.
The temperature sensing network is showed as below.
The input voltage sense network is shown below,
choose RUP, RDOWN to set the input voltage threshold
VINT:
IN
SY6953
RUP
VSEN
RDOWN
Figure6. Input Voltage Sense Network
VINT
VVSEN_DPM (RDOWN RUP )
VVSEN_DPM
RDOWN
is 1.2V.
Unit: V
Charge Current Sense Resistor Rs
VDD
SY6953
The charging current sense resistor RS is calculated as
below:
R1
NTC
R2
RNTC
10kΩ at 25oC
Figure5. NTC Resistors
For JEITA standard, T1=0ºC, T2=10oC, T3=45oC,
T5=60oC.
NTC resistors should be chosen at R1=5.24kΩ,
R2=30.28kΩ.
Input Voltage Threshold for Input Power Limit
SY6953 will monitor input voltage by measuring the
VSEN voltage, when VSEN drops below the internal
1.2V reference, SY6953 will decrease the duty cycle
to reduce the charge current.
AN_SY6953 Rev. 0.0A
© 2019 Silergy Corp.
RS =
30mV ,
I CC
Unit: mΩ
where the ICC is the battery constant charge current,
unit is ampere.
Timer Capacitor CTIM
The charger also provides a programmable charge
timer. The charge time is programmed by the
capacitor connected between the TIM pin and GND.
The capacitance is given by the formula:
CTIM=2×10-11S×tCC
Unit: F
tCC is the permitted fast charge time, unit is second.
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AN_SY6953
Input Capacitor CPMID
The main input capacitor is connected between PMID
pin to PGND. It can absorb input ripple current from
the Buck stage, which is given by below equation.
I RMS I CHG
VBAT (VIN VBAT )
VIN
The maximum value of this RMS ripple current in the
application must be smaller than the rated RMS
current in the chosen capacitor datasheet. Care should
be taken to minimize the loop area formed by CPMID,
and PMID and PGND pins.
To minimize the potential noise problem, IN should
be decoupled to PGND with typical 1μF
capacitance, X7R or a better grade ceramic capacitor.
Output Capacitor CBAT
The output capacitor in parallel with the battery is
used for absorbing the high frequency switching
ripple current and smoothing the output voltage. The
RMS value of the output ripple current IRMS is
calculated as follow.
I RMS
VIN D (1 D)
12 L f SW
Where the duty cycle D is the ratio of the output
voltage (battery voltage) over the input voltage for
CCM mode which is typical operation for the battery
charger. During the battery charge period, battery
voltage varies from its initial battery voltage to the
rated voltage. The maximum value of this RMS
ripple current in the application must be smaller than
the rated RMS current in the chosen capacitor
datasheet. A typical 20μF ceramic capacitor is
recommended to absorb this current and also has
small size.
Output Inductor L
There are several considerations in choosing the
inductor.
1) Choose the inductance to provide the desired
ripple current. It is suggested to choose the ripple
current to be about 20%-40% of the maximum
charge current ICC. The inductance is calculated
as:
L
VBAT _ REG (1 VBAT _ REG /VIN )
f SW I CC (20%~40%)
AN_SY6953 Rev. 0.0A
© 2019 Silergy Corp.
where fSW is the switching frequency and VIN is
the input voltage in the application
SY6953 is quite tolerant of different ripple
current amplitude. Consequently, the final choice
of inductance can be slightly off the calculation
value without significantly impacting the
performance.
2) The saturation current rating of the inductor must
be selected to be greater than the maximum peak
inductor current under all the range of battery
voltage and full load conditions.
ISAT ICC
VBAT _ REG (1 VBAT _ REG /VIN )
2 f SW L
The maximum peak inductor current happens
when battery voltage is equivalent with half of
input voltage.
3) The DCR of the inductor and the core loss at the
switching frequency must be low enough to
achieve the desired efficiency requirement. It is
desirable to choose an inductor with
DCR
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