RT9534 - Richtek

RT9534
High Efficiency Switching Mode Battery Charger
General Description
Features
The RT9534 is a PWM switch mode battery charger

Fast Charging for Li-Ion, NiMH and NiCd Batteries
controller to fast charge single or multiple Li-Ion, NiMH

Adjustable Battery Voltages from 2.5V to 22V
and NiCd batteries, using constant current or constant

High Efficiency : Up to 95%
voltage control. Maximum current can be easily

Charging Current Programmed by Resistor
programmed by external resistor. The constant voltage

Precision 0.5% Charging Voltage Accuracy
output can support up to 22V with 0.5% accuracy.

Provide 5% Charging Current Accuracy
A third control loop limits the input current drawing from

Input Current Limit Maximizes Charging Rate
the adapter during charging. This allows simultaneous

Synchronous Converter with 400kHz Switching
operation of the equipment and fast battery charging
Frequency
without over loading to the adapter.

Flag Indicates Li-Ion Charge Completion
The RT9534 can charge batteries from 2.5V to 22V

Auto Shutdown with Adapter Removal
with dropout voltage as low as 0.4V. A diode is not
required in series with the battery because the charger
automatically enters a 10μA sleep mode when the
Applications

Notebook Computers

Portable Instruments

Chargers for Li-lon, NiMH, NiCd and Lead Acid
adapter is unplugged. A logic output indicates Li-Ion full
charge when current drops to 20% of the full-scale
Rechargeable Batteries
programmed charge current.
The RT9534 is available in WQFN-24L 4x4 Package.
Simplified Application Circuit
M1
SI4435
VIN
RS4
CIN
R2
C2
D2
MMSD4148T1G
C1
R1
V5V
ACN
To VHH Pin
C7
EN
M2
SI4412
R6
RT9534
R5
M3
SI4412
BG
MODE
S2
FBR
C3
C4
RS3
RS2


BATT
RF2
CBATT
SGND
C5
RS1
RF2
RF1+200 
PGND
VC
R4
L1
SW
ISET
R3
VBATT = 2.5   1+
C8
TG
ACDRV
VIN


BOOT
ACP
S1
D3
MMSD4148T1G
SGND
V5V
RF1
NTC
VFB
R9
STATUS
C6
August 2015
Css
C9
R 10
SNS
RNTC
C11
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9534-00
SNSH
SNSL
VHH
200
BATT
SS
is a registered trademark of Richtek Technology Corporation.
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1
RT9534
Ordering Information
Pin Configurations
RT9534
(TOP VIEW)
Note :
Richtek products are :

RoHS compliant and compatible with the current
requirements of IPC/JEDEC J-STD-020.

Suitable for use in SnPb or Pb-free soldering processes.
24 23 22 21 20 19
EN
NTC
VC
ISET
FBR
VFB
1
18
2
17
3
SGND
4
25
5
6
16
15
14
13
7
8
BOOT
TG
SW
PGND
BG
VIN
9 10 11 12
BATT
SNSL
SNSH
SNS
VHH
V5V
Lead Plating System
G : Green (Halogen Free and Pb Free)
ACDRV
ACP
ACN
SS
STATUS
MODE
Package Type
QW : WQFN-24L 4x4 (W-Type)
(Exposed Pad-Option 1)
Marking Information
1B= : Product Code
1B=YM
DNN
YMDNN : Date Code
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WQFN-24L 4x4
is a registered trademark of Richtek Technology Corporation.
DS9534-00
August 2015
RT9534
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
EN
2
NTC
3
VC
4
ISET
5
FBR
6
VFB
7
BATT
8
SNSL
Enable Control Input (Active High). It must be connected to a logical voltage or
pulled up to VIN with a 100k resistor.
Input for an external NTC thermistor for battery temperature monitoring.
Control Signal of the Inner Loop of the Current Mode PWM. A capacitor of at
least 0.1F with a serial resistor to GND filters out the current ripple.
Charge Current Setting and System Loop Compensation Pin. Connect a
resistor from this pin to ground to set the charge current.
Negative Terminal of External Resistor Divider for Battery Voltage Feedback. A
200 resistor connect from FBR to GND.
Battery Voltage Feedback. Using an external resistor divider to set battery full
charge voltage.
Battery Voltage Sensing Input. A 10F or larger X5R ceramic capacitor is
recommended for filtering charge current ripple and stability purpose.
Negative Terminal for Sensing Charge Current.
9
SNSH
Positive Terminal for Sensing Charge Current.
10
SNS
Input terminal for reversal current comparator.
11
VHH
12
V5V
13
VIN
14
BG
Output of low side driver.
15
PGND
16
SW
Power Ground.
Switch Node. This pin switches between ground and VIN with high dv/dt rates.
Care needs to be taken in the PCB layout to keep this node from coupling to other
sensitive nodes.
17
TG
Output of High-Side Driver with BOOT and SW as Floating Power and Return.
18
BOOT
Bootstrap Supply for the High-Side Gate Driver and Control Circuitry. In normal
operation, VBOOT ≈ VSW + 5V.
19
MODE
Input control pin for CCM of DCM mode selection. Tying MODE pin to V5V for
CCM mode selection and GND for DCM.
20
STATUS
Flag to Indicate Charge Completion. It turns to logical high when the charge
current drops blew 20% of the setting charge current. A 0.1F capacitor from
STATUS to ground is needed to filter the sampled charge current ripple.
21
SS
Soft-Start Control Input. SS controls the soft-start time. Connect a capacitor
from SS pin to GND to set the soft-start time.
22
ACN
Negative Terminal to Sense Input Current. A filter is needed to filter out the
500kHz switching noise.
23
ACP
Positive Terminal to Sense Input Current.
24
ACDRV
Drive Signal for the Gate of Input Power PFET.
25
(Exposed Pad)
SGND
Signal Ground. The exposed pad must be soldered to a large PCB and
connected to GND for maximum thermal dissipation.
To supply the current sense amplifier CA for very low dropout condition. It must
be connected as shown in the typical application circuit or connected to VIN if
VIN is always larger than BATT by at least 3.6V.
Output of Internal 5V LDO. Connect a 1F ceramic capacitor from this pin to
GND for stability.
Input Power Supply. Connect a low ESR capacitor of 10F or higher from this
pin to ground for good bypass.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9534-00
August 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
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RT9534
Function Block Diagram
VIN
ACDRV
NTC
ACN
R1
200k
5V
1.4V
THERMAL
CMP
C3
EN
DRIVER
0.5uA
5V
VREF
2.5V
REFERENCE
SD
VIN
UVLO
V5V
LDO
+
VIN
BATT
C2
0.4V
UVLO
SGND
3.9V
IVA
ICHG
VHH
STATUS
SLOP COMP
ICHG
5
OSCILLATOR
R2
SNSH
CA
SNSL
ICHG
BOOT
PWM
S
C1
VFB
VREF
2.5V
FBR
VA
VREF
2.5V
IVA
TG
R
EA
SW
200
SD
1.3V
100mV
+
ACP
ICL
Soft-Start
V5V
CL
ACN
LOGIC
BG
SNS
BATT
PGND
REV
ISET
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
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SS
VC
MODE
is a registered trademark of Richtek Technology Corporation.
DS9534-00
August 2015
RT9534
Operation
The RT9534 is a current mode PWM step-down
CL Amplifier
switching charger controller. The battery DC charge
The amplifier CL monitors and limits the input current,
current is programmed by a resistor R4 at the ISET pin
normally from the AC adapter, to a preset level (100mV
and the ratio of sense resistor RS2 over RS1 in the
/ RS4). At input current limit, CL will supply the
typical application circuit. Amplifier CA converts the
programming current at ISET pin, thus reducing battery
charge current through RS1 to a much lower sampled
charging current.
current ICHG (ICHG = IBATT x RS1 / RS2) fed into the
ISET pin. Amplifier EA compares the output of CA with
2.5V reference voltage and drives the PWM loop to
force them to be equal. Note that ICHG has both AC
and DC components. High DC accuracy is achieved
Charge STATUS
When the charger is in voltage mode and the charge
current level is reduced to 20%, STATUS pin will turn to
logic high. This charge completion signal can be used
to start a timer for charge termination. A 0.1F
with averaging filter R3 and C3 at ISET pin. ICHG is
mirrored to go through R4 and generates a ramp signal
that is fed to the PWM control comparator, forming the
capacitor from STATUS to ground is needed to filter the
sampled charging current ripple.
current mode inner loop. An internal LDO generates a
ACDRV Driver
5V to power topside FET gate driver. For batteries like
The ACDRV pin drives an external P-MOSFET to avoid
lithium that require both constant current and constant
reverse current from battery to input supply. When
voltage charging, the 0.5% 2.5V reference and the
input supply is removed, the RT9534 goes into a low
voltage amplifier VA reduce the charge current when
current, 10A maximum, sleep mode as VIN drops
battery voltage reaches the normal charge voltage level.
below the battery voltage.
For NiMH and NiCd, VA can be used for over voltage
protection.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9534-00
August 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
RT9534
Absolute Maximum Ratings
(Note 1)

VIN, SW, EN, ACN, VHH to GND --------------------------------------------------------- 0.3V to 30V

ACDRV ------------------------------------------------------------------------------------------- (ACN 6V) to (ACN  0.3V)

ACP ------------------------------------------------------------------------------------------------ (ACN 0.3V) to (ACN  0.6V)

BATT to GND------------------------------------------------------------------------------------ 0.3V to 28V

ISET, VC, VFB, V5V, BG to GND ---------------------------------------------------------- 0.3V to 6V

SNSL ---------------------------------------------------------------------------------------------- (BATT  0.3V) to (BATT  0.3V)

SNSH---------------------------------------------------------------------------------------------- (SNSL  0.3V) to (SNSL  0.3V)

BOOT --------------------------------------------------------------------------------------------- (SW  0.3V) to (SW  6V)

TG -------------------------------------------------------------------------------------------------- (SW 0.3V) to (BOOT + 0.3V)

Power Dissipation, PD @ TA = 25C
WQFN-24L 4x4 --------------------------------------------------------------------------------- 3.57W

Package Thermal Resistance
(Note 2)
WQFN-24L 4x4, JA --------------------------------------------------------------------------- 28C/W
WQFN-24L 4x4, JC --------------------------------------------------------------------------- 7C/W

Lead Temperature (Soldering, 10 sec.) --------------------------------------------------- 260C

Junction Temperature ------------------------------------------------------------------------- 150C

Storage Temperature Range ---------------------------------------------------------------- 65C to 150C

ESD Susceptibility
(Note 3)
HBM (Human Body Model) ------------------------------------------------------------------ 2kV
MM (Machine Model) -------------------------------------------------------------------------- 200V
Recommended Operating Conditions
(Note 4)

Supply Input Voltage -------------------------------------------------------------------------- 4.5V to 28V

Battery Voltage, VBAT ------------------------------------------------------------------------ 2.5V to 22V

Ambient Temperature Range---------------------------------------------------------------- 40C to 85C

Junction Temperature Range --------------------------------------------------------------- 40C to 125C
Electrical Characteristics
(VIN = VBAT + 3V, VBAT is the full charge voltage, pull-up EN to VIN with 100k resistor, TA = 25C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
0.5
1.3
2
mA
Overall
Supply Quiescent Current
IQ
No Charge Current
Supply Shutdown Current
ISD
VEN = 0
--
--
12
A
Reverse Current from Battery
IREV
VIN Floating
--
--
10
A
VIN Under-Voltage Lockout
VUVLO
3.6
3.8
4.3
V
VIN Under-Voltage Lockout
Hysteresis
VUVLO_HYS
--
300
--
mV
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
DS9534-00
August 2015
RT9534
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
2.488
2.5
2.512
V
--
--
0.1
A
Reference
Reference Voltage
VFB
FB Bias current
IFB
VFB = 2.5V
FBR to GND Resistance
RFBR
SD = 2V
160
200
220

SD = 0V
--
--
1
A
R4 = 10k, RS2 = RS3
= 402, Measure the
Voltage Drop Across
RS1
95
100
105
mV
--
--
−0.5
mA
FBR leakage Current
Charge Current
Full-Scale Charge Current
Sense Voltage
VICHG
ISET Output Current
IISET
Termination current Set Factor
VITM
SNSL Bias Current
ISNSH
1/5-Scale Charge
Current when STATUS
from Low to High
No Charge Current
SNSH Bias Current
ISNSH
No Charge Current
--
20
27
%
−36
−12
−6
A
−36
−12
−6
A
--
--
3.6
V
--
0.3
0.4
V
Battery Voltage
VHH Minimum Voltage with
Respect to BATT
VIN Minimum Voltage with
Respect to BATT
VHH Input Current
VHH
VDROP

IVHH
VIN = 28V
150
180
210
A
BATT Bias Current
IBATT
VBATT = 25V
0.8
2
8
A
VC Pin Current
IVC
VVC = 0V
−25
−15
−1
A
SNS Bias Current
ISNS
−36
−12
−6
A
Input Current Limit
Input Current Limit Sense
Voltage
VILMT
Measure the Voltage
Drop Across RS4
95
100
105
mV
ACN Input Current
IACN
VACP − VACN = 0.1V
5
16
37
A
ACP Input Current
IACP
VACP − VACN = 0.1V
25
50
80
A
ACDRV ON Voltage
VACON
4
5.4
6
V
ACDRV OFF Voltage
VACOFF
--
--
0.1
V
ARDRV Pull-Down Current
IACPD
5
10
40
A
ARDRV Pull-Up Current
IACPU
−10
−5
−2
A
350
400
450
kHz
--
25
75
ns
Measure the Voltage
(VACN − VACDRV)
Measure the Voltage
(VACN − VACDRV), VEN =
0V
VACN − VACDRV = 3.8V
VACN − VACDRV = 0.5V,
VEN = 0V
Switch Characteristics
Switching Frequency
fOSC
TG Rise Time
TR
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9534-00
August 2015
VBOOT − VSW = 5V, 1nF
Load at TG Pin
is a registered trademark of Richtek Technology Corporation.
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7
RT9534
Parameter
Symbol
Test Conditions
VBOOT − VSW = 5V, 1nF
Min
Typ
Max
Unit
--
25
75
ns
TG Fall Time
TF
BG Rise Time
BR
CBG =1nF
--
25
75
ns
BG Fall Time
BF
CBG =1nF
--
25
75
ns
Maximum Duty
95
--
--
%
Dead Time
--
20
--
ns
Load at TG Pin
TG ON Voltage
VTG
VTG – VSW
--
4.2
--
V
BG ON Voltage
VTG
VBG
--
4.2
--
V
BOOT Leakage Current
IBOOT
VBOOT = 28V, VEN = 0V
--
1
--
A
VVC = 0V
95
--
--
%
VSW = 28V, VEN = 0V
--
--
10
A
4
5.2
6
V
--
5
--
V
Maximum Duty
SW Leakage Current
ILKGL
Regulator and Logic Characteristics
LDO Output Voltage
VLDO
STATUS High Voltage
EN Input Voltage
50mA Load at V5V, VVC
= 0V
STATUS Cap = 1F
Logic-High
VENH
2.5
--
--
Logic-Low
VENL
--
--
0.6
--
--
10
A
0V ≤ VEN ≤ 5V
V
EN Input Current
IEN
Soft-Start Sourcing Current
ISS
1.5
3.3
6
A
MODE Pin Threshold ON
VMODE
0.8
--
3.5
V
Thermal Comparator and Protection
NTC Voltage Rising, 1% 73.5%  75% 
Hysteresis
VV5V
VV5V
NTC Voltage Rising, 1% 31%  32.5%
Hysteresis
VV5V
 VV5V
---
NTC Threshold, Cold
VCOLD
NTC Threshold, Hot
VHOT
NTC Bias Current
INTC
Thermal Shutdown Temperature
TSD
--
Thermal Shutdown Hysteresis
TSD
--
76.5%
 VV5V
34% 
VV5V
0.1
A
160
--
°C
30
--
°C
V
V
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect
device reliability.
Note 2. JA is measured at TA = 25C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. JC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
DS9534-00
August 2015
RT9534
Typical Application Circuit
M1
SI4435
VIN
RS4
50 mohm
R2
56
CIN
10μF
C1
33nF
R1
100k
C2
10μFx2
22
23
24
S1
R3
(Optional)
1
C3
(Optional)
R5
1k
C5
(Optional)
EN
VIN
6
TG
ACDRV
ISET
25
BOOT
ACP
4
5
C4
1μF
ACN
13
3
R4
10k
V5V
SW
BG
PGND
VC
MODE
FBR
NTC
VFB
STATUS
11
C6
0.1μF
8
17
M2
SI4412
R6
10
C8
0.1μF
L1
6.8μH


VBATT = 2.5   1+
RS1
50 mohm
RF2


RF1+200 
BATT
9
14
M3
SI4412
RS3
402
15
RS2
402
TVS
1430k
19
S2
SGND
V5V
CBATT
10μF
R7
250k
2
R9
500k
20
21
Css
0.1μF
C9
0.1μF
R10
500k
SNS
SNSH
BATT
7
SNSL
VHH
SS
200
To VHH Pin
C7
1μF
18
16
D3
MMSD4148T1G
R8
RT9534
SGND
D2
MMSD4148T1G
12
10
C11
0.1μF
Note :
(1). For application with removable battery, a TVS with appropriate rating is required as shown above.
(2). VIN = 18V to 28V, 4 cell, ICHARGE = 2A
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9534-00
August 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
9
RT9534
Typical Operating Characteristics
Efficiency vs. Charge Current
100
95
95
90
90
Efficiency (%)
Efficiency (%)
Efficiency vs. Supply Voltage
100
85
1 Cell : VBATT
2 Cell : VBATT
3 Cell : VBATT
4 Cell : VBATT
5 Cell : VBATT
80
75
= 4V
= 8V
= 12V
= 16V
= 20V
85
1 Cell : VIN = 10V, VBATT
2 Cell : VIN = 12V, VBATT
3 Cell : VIN = 16V, VBATT
4 Cell : VIN = 20V, VBATT
5 Cell : VIN = 28V, VBATT
80
75
IBATT = 2A
70
70
0
5
10
15
20
25
1
30
2
4
5
Quiescent Current vs. Temperature
Charge Current vs. Supply Voltage
0.9
2.20
2.12
2.08
2.04
= 4V
= 8V
= 12V
= 16V
= 20V
0.8
Quiescent Current(mA)
1 Cell : VBATT
2 Cell : VBATT
3 Cell : VBATT
4 Cell : VBATT
5 Cell : VBATT
2.16
Charge Current (A)
3
Charge Current (A)
Supply Voltage (V)
2.00
1.96
1.92
1.88
0.7
0.6
0.5
0.4
0.3
0.2
VIN = 28V
VIN = 12V
0.1
1.84
0
1.80
0
5
10
15
20
25
-50
30
-25
25
50
75
100
125
V5V Voltage vs. Temperature
Shutdown Current vs. Temperature
5.00
25
4.95
V5V Voltage (V)
30
20
15
VIN = 28V
VIN = 12V
10
0
Temperature(℃)
Supply Voltage (V)
Shutdown Current(μA)
= 4V
= 8V
= 12V
= 16V
= 22V
4.90
4.85
4.80
5
4.75
0
4.70
VIN = 12V, IV5V = 40mA
-50
-25
0
25
50
75
100
Temperature (℃)
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10
125
-50
-25
0
25
50
75
100
125
Temperature (℃)
is a registered trademark of Richtek Technology Corporation.
DS9534-00
August 2015
RT9534
VICHG vs. Temperature
Feedback Voltage vs. Temperature
110
2.6
108
106
Feedback Voltage (V)
2.55
VICHG (mV)
104
102
100
98
96
VIN = 4.5V
VIN = 12V
VIN = 28V
94
92
-25
0
25
50
75
100
2.45
2.4
2.3
125
-50
Temperature (°C)
25
50
75
100
125
BATT Bias Current vs.Temperature
12
395
BATT Bias Current (A)
Switching Frequency (kHz)
0
14
400
390
385
380
375
10
8
6
4
2
370
0
3
6
9
12
15
18
21
24
27
30
-50
-25
0
25
50
75
Input Voltage (V)
Temperature (℃)
Charge Enable
Charge Enable
100
125
EN
(2V/Div)
VBATT
(5V/Div)
VBATT
(5V/Div)
SW-GND
(10V/Div)
SW-GND
(10V/Div)
VIN = 16V, VBATT = 12V, IBATT = 2A
Time (2.5ms/Div)
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9534-00
-25
Temperature (°C)
Switching Frequency vs. Input Voltage
EN
(2V/Div)
IBATT
(1A/Div)
VIN = 4.5V
VIN = 12V
VIN = 28V
2.35
90
-50
2.5
August 2015
IBATT
(1A/Div)
VIN = 16V
VBATT = 12V
IBATT = 2A
Time (2.5ms/Div)
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RT9534
Adapter Insert
Adapter Remove
SW-GND
(10V/Div)
SW-GND
(10V/Div)
VBATT
(2V/Div)
VIN
(5V/Div)
IBATT
(1A/Div)
VBATT
(2V/Div)
VIN
(5V/Div)
VIN = 16V, VBATT = 12V, IBATT = 2A
IBATT
(1A/Div)
Time (25ms/Div)
Time (25ms/Div)
CCM Switching
DCM Switching
TG
(20V/Div)
VBATT
(5V/Div)
TG
(20V/Div)
VBATT
(5V/Div)
BG
(5V/Div)
BG
(5V/Div)
IL
(500mA/Div)
IL
(500mA/Div)
VIN = 16V, VBATT = 12V, IBATT = 100mA
Time (1s/Div)
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12
VIN = 16V, VBATT = 12V
IBATT = 2A
VIN = 16V, VBATT = 12V, IBATT = 100mA
Time (1s/Div)
is a registered trademark of Richtek Technology Corporation.
DS9534-00
August 2015
RT9534
Application Information
Input and Output Capacitors
and the battery impedance is raised to 4 with a bead
In the typical application circuit, the input capacitor (C2)
or inductor, only 5% of the ripple current will flow in the
is assumed to absorb all input switching ripple current
battery.
in the converter, so it must have adequate ripple
current rating. Typically, at high charging currents, the
converter will operate in continuous conduction mode.
In this case, the RMS current IRMSIN of the input
capacitor C2 can be estimated by the equation:
IRMSIN = IBATT  D  D2
Inductor
The inductor value will be changed for more or less
current ripple. The higher the inductance, the lower the
current ripple will be. As the physical size is kept the
same, typically, higher inductance will result in higher
series resistance and lower saturation current. A good
tradeoff is to choose the inductor so that the current
Where IBATT is the battery charge current and D is the
duty cycle. In worst case, the RMS ripple current will be
equal to one half of output charging current at 50% duty
cycle. For example, IBATT = 2A, the maximum RMS
current will be 1A. A low-ESR ceramic capacitor such
as X7R or X5R is preferred for the input-decoupling
capacitor and should be placed to the drain of the
high-side MOSFET and source of the low-side
MOSFET as close as possible. The voltage rating of
the capacitor must be higher than the normal input
voltage level. Above 20F capacitance is suggested for
ripple is approximately 30% to 50% of the full-scale
charge current. The inductor value is calculated as :
L1 =
VBATT   VVIN  VBATT 
VVIN  fOSC  ΔIL
Where IL is the inductor current ripple. For example,
VVIN = 19V, choose the inductor current ripple to be
40% of the full-scale charge current in the typical
application circuit for 2A, 2-cell battery charger, IL =
0.8A, VBATT = 8.4V, calculate L1 to be 12H. So
choose L1 to be 10H which is close to 12H.
typical of 2A charging current.
Soft-Start and Under-Voltage Lockout
The output capacitor (CBATT) is also assumed to
The soft-start is controlled by the voltage rise time at
absorb output switching current ripple. The general
VC pin. There are internal soft-start and external
formula for capacitor current is :
soft-start in the RT9534. With a 1F capacitor, time to
IRMSCB
 VBATT 
VBATT   1

VVIN 

=
2  3  L1 fosc
reach full charge current is about 60ms and it is
assumed that input voltage to the charger will reach full
value in less than 60ms. The capacitor can be
For example, VVIN = 19V, VBATT = 8.4V, L1 = 10H,
increased if longer input start-up times are needed.
and f OSC = 400kHz, IRMS = 0.15A.
For the RT9534, it provides Under-Voltage Lockout
EMI considerations usually make it desirable to
(UVLO) protection. If LDO output voltage is lower than
minimize ripple current in the battery leads. Beads or
3.9V, the internal top side power FET and input power
inductors may be added to increase battery impedance
FET M1 will be cut off. This will protect the adapter from
at the 400kHz switching frequency. Switching ripple
entering a quasi “latch” state where the adapter output
current splits between the battery and the output
stays in a current limited state at reduced output
capacitor depending on the ESR of the output capacitor
voltage.
and the battery impedance. If the ESR of COUT is 0.2
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9534-00
August 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
13
RT9534
Adapter Current Limiting
5.5k to 60k range.
An important feature of RT9534 is the ability to
For for 40C to 85C application temperature range,
automatically adjust charge current to a level which
the value for R4 must be within 6k to 30k range.
avoids overloading the wall adapter. This allows the
product to operate, and at the same time batteries are
being charged without complex load management
algorithms. Additionally, batteries will automatically be
charged at the maximum possible rate of which the
adapter is capable. This is accomplished by sensing
total adapter output current and adjusting charge
current downward if a preset adapter current limit is
It is critical to have a good Kelvin connection on the
current sense resistor RS1 to minimize stray resistive
and inductive pickup. RS1 should have low parasitic
inductance (typical 3nH or less). The layout path from
RS2 and RS3 to RS1 should be kept away from the fast
switching SW node. A 1nF ceramic capacitor can be
used across SNSH and SNSL and be kept away from
the fast switching SW node.
exceeded. Amplifier CL in typical application circuit
senses the voltage across RS4, connected between
Battery Voltage Regulation
the ACP and ACN pins. When this voltage exceeds
The RT9534 uses high-accuracy voltage bandgap and
100mV, the amplifier will override programmed charge
regulator for the high charging-voltage accuracy. The
current to limit adapter current to 100mV/RS4. A low
charge voltage is programmed via a resistor divider
pass filter formed by 56 and 33nF is required to
from the battery to ground, with the midpoint tied to the
eliminate switching noise.
VFB pin. The voltage at the VFB pin is regulated to
2.5V, giving the following equation for the regulation
Full-Scale Charge Current Programming
The basic formula for full-scale charge current is (see
Block Diagram) :
voltage :
RF2 

VBATT = 2.5  1 +
RF1+200 

 VREF   RS2 
IBATT = 


 R4   RS1 
where RF2 is connected from VFB to the battery and
Where R4 is the total resistance from ISET pin to
RF1 is connected from VFB to GND.
ground. For the sense amplifier CA biasing purpose,
RS3 should have the same value as RS2 with 1%
accuracy. For example, 2A full-scale charging current is
needed. For low power dissipation on RS1 and enough
signal to drive the amplifier CA, let RS1 = 100mV / 2A =
50m. This limits RS1 power to 0.2W. Let R4 = 10k,
then :
IBATT  R4  RS1 2A 10k  0.05
RS2 = RS3 =
=
= 400Ω
VREF
2.5V
Charging
The 2A Battery Charger (typical application circuit)
charges lithium-ion batteries at a constant 2A until
battery voltage reaches the setting value. The charger
will then automatically go into a constant voltage mode
with current decreasing to near zero over time as the
battery reaches full charge.
Charging Completion
Note that for charge current accuracy and noise
Some battery manufacturers recommend termination of
immunity, 100mV full scale level across the sense
constant voltage float mode after charge current has
resistor RS1 is required. Consequently, both RS2 and
dropped below a specified level (typically around 20%
RS3 should be 399. For for 0C to 85C application
of the full-scale charge current) and a further time-out
temperature range, the value for R4 must be within
period of 30 minutes to 90 minutes has elapsed. Check
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14
is a registered trademark of Richtek Technology Corporation.
DS9534-00
August 2015
RT9534
with manufacturers for details. The RT9534 provides a
VACN. In sleep mode, when VIN is removed, ACDRV
signal at the STATUS pin when charging is in voltage
will clamp M1 VSG to less than 0.1V.
mode and charge current is reduced to 20% of
full-scale charge current, assuming full-scale charge
current is programmed to have 100mV across the
current sense resistor (VRS1).
The charge current sample ICHG is compared with the
output current IVA of voltage amplifier VA. When the
charge current drops to 20% of full-scale charge
current, IVA will be equal to 20% of ICHG and the
STATUS pin voltage will go logic high and can be used
to start an external timer. When this feature is used, a
capacitor of at least 0.1F is required at the STATUS
pin to filter out the switching noise. If this feature is not
used, the capacitor is not needed.
Dropout Operation
The RT9534 can charge the battery even when VIN
goes as low as 2V above the combined voltages of the
battery and the drops on the sense resistor as well as
parasitic wiring. This low VIN sometimes forces 100%
duty cycle and TG stays on for many switching cycles.
While TG stays on, the voltage VBOOT across the
capacitor C8 drops down slowly because the current
sink at BOOT pin. C8 needs to be recharged before
VBOOT drops too low to keep the topside switch on.
A unique design allows the RT9534 to operate under
these conditions. If SW pin voltage keeps larger than
1.3V for 32 oscillation periods, topside power FET will
be turned off and an internal FET will be turned on to
Shutdown
When adapter power is removed, VIN will drift down.
As soon as VIN goes down to 0.1V above VBATT, the
RT9534 will go into sleep mode drawing only ~10μA
from the battery. There are two ways to stop switching:
pulling the EN pin low or pulling the VC pin low. Pulling
the EN pin low will shut down the whole chip. Pulling
the VC pin low will only stop switching and LDO stays
work. Make sure there is a pull-up resistor on the EN
pin even if the EN pin is not used, otherwise internal
pull-down current will keep the EN pin low to shut down
mode when power turns on.
Charger Protection
If the VIN connector of typical application circuit can be
instantaneously shorted to ground, the P-MOSFET M1
must be quickly turned off, otherwise, high reverse
surge current might damage M1. An internal transient
enhancement circuit is designed to quickly charge
ACDRV pin voltage to ACN pin voltage.
Note that the RT9534 will operate even when VBATT is
grounded. If VBATT of typical application circuit charger
gets shorted to ground very quickly from a high battery
voltage, slow loop response may allow charge current
to build up and damage the topside N-MOSFET M2. A
small diode from the EN pin to VBATT will shut down
switching and protect the charger.
pull SW pin down. This function refreshes VBOOT
Temperature Qualification
voltage to a higher value. It is important to use 0.1F to
The controller RT9534 continuously monitors battery
hold VBOOT up for a sufficient amount of time. The
temperature by measuring the voltage between the
P-MOSFET M1 is optional and can be replaced with a
NTC pin and GND. A negative temperature coefficient
diode if VIN is at least 2.5V higher than VBATT. The
thermistor (NTC) and an external voltage divider
gate control pin ACDRV turns on M1 when V5V gets up
typically develop this voltage. The controller compares
above the under-voltage lockout level and is clamped
this voltage against its internal thresholds to determine
internally to 5V below VACN. In sleep mode, when VIN
if charging is allowed. To initiate a charge cycle, the
is removed, ACDRV will clamped internally to 5V below
battery temperature must be within the VCOLD. If
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9534-00
August 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
15
RT9534
battery temperature is outside of this range, the
ambient thermal resistance.
controller suspends charge and the safety timer and
For recommended operating condition specifications,
waits until the battery temperature is within the VCOLD
the maximum junction temperature is 125C. The
to VHOT range. If the battery temperature is outside of
junction to ambient thermal resistance, JA, is layout
this range, the controller suspends charge and waits
dependent. For WQFN-24L 4x4 package, the thermal
until the battery temperature is within the VCOLD to
resistance, JA, is 28C/W on a standard JEDEC 51-7
VHOT range. The controller suspends charge by
four-layer thermal test board. The maximum power
turning off the PWM charge FETs.
dissipation at TA = 25C can be calculated by the
Assuming a 103AT NTC thermistor on the battery pack
following formula :
as shown in the below, the values of RT1 and RT2 can
PD(MAX) = (125C  25C) / (28C/W) = 3.57W for
be determined by using the following equations:
WQFN-24L 4x4 package
1 
 1
VV5V  RTHCOLD  RTHHOT  


V
V
HOT 
 COLD
RT2 =
 VV5V

 VV5V

RTHHOT  
 1  RTHCOLD  
 1
V
V
 HOT

 COLD

The maximum power dissipation depends on the
VV5V
1
VCOLD
RT1 =
1
1

RT2 RTHCOLD
temperature on the maximum power dissipation.
operating ambient temperature for fixed TJ(MAX) and
thermal resistance, JA. The derating curve in Figure 1
allows the designer to see the effect of rising ambient
V5V
RT9534
RT1
NTC
RT2
RTH
103AT
TS Resistor Network
Where RTHCOLD and RTHHOT which have defined in the
spec of the 103AT NTC thermistor.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature.
The maximum power dissipation can be calculated by
the following formula :
PD(MAX) = (TJ(MAX)  TA) / JA
where TJ(MAX) is the maximum junction temperature,
TA is the ambient temperature, and JA is the junction to
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is a registered trademark of Richtek Technology Corporation.
DS9534-00
August 2015
Maximum Power Dissipation (W)1
RT9534
5.0
Four-Layer PCB
4.0
3.0
2.0
1.0
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 1. Derating Curve of Maximum Power
Dissipation
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9534-00
August 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
17
RT9534
Outline Dimension
Symbol
D2
E2
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
0.700
0.800
0.028
0.031
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.180
0.300
0.007
0.012
D
3.950
4.050
0.156
0.159
Option 1
2.400
2.500
0.094
0.098
Option 2
2.650
2.750
0.104
0.108
E
3.950
4.050
0.156
0.159
Option 1
2.400
2.500
0.094
0.098
Option 2
2.650
2.750
0.104
0.108
e
L
0.500
0.350
0.020
0.450
0.014
0.018
W-Type 24L QFN 4x4 Package
Richtek Technology Corporation
14F, No. 8, Tai Yuen 1st Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume
responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and
reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may
result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.
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18
is a registered trademark of Richtek Technology Corporation.
DS9534-00
August 2015