RT9535A
High Efficiency Switching Mode Battery Charger
General Description
Features
The RT9535A 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
500kHz Switching Frequency
the adapter during charging. This allows simultaneous
Auto Shutdown with Adapter Removal
operation of the equipment and fast battery charging
Applications
without over loading to the adapter.
Notebook Computers
Portable Instruments
Chargers for Li-lon, NiMH, NiCd and Lead Acid
The RT9535A can charge batteries from 2.5V to 22V
with dropout voltage as low as 0.4V.
The RT9535A is available in the WQFN-16L 4X4
Rechargeable Batteries
package.
Simplified Application Circuit
D4
VIN
C1
R1
R2
HSD
EN
VIN
CIN
C2
RT9535A
D2
D3
To RS3
VHH
V5V
R7
ISET
VC
R3
R4
C3
C6
NTC
C7
R6
RNTC
SS
R5
C5
R8
C4
BOOT
C8
GND
L1
RS1
VBATT
SW
VFB
VFB
PGND
VHH
VHH
RF2
D1
SNSH
RS3
RS2
CBATT
To VFB
RF1
SNSL
BATT
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9535A-03
June 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
RT9535A
Marking Information
Ordering Information
RT9535A
Package Type
QW : WQFN-16L 4x4 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
1Y=YM
DNN
1Y= : Product Code
YMDNN : Date Code
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
Pin Configurations
V5V
VIN
BOOT
HSD
(TOP VIEW)
16
15
14
13
EN
1
12
SW
11
PGND
10
SNSH
9
SNSL
SS
2
ISET
3
VC
4
GND
5
6
7
8
NTC
VFB
VHH
BATT
17
WQFN-16L 4x4
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
is a registered trademark of Richtek Technology Corporation.
DS9535A-03
June 2015
RT9535A
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
EN
Enable Control Input (Active High). It must be connected to a logical voltage or
pulled up to VIN with a 100k resistor.
2
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.
3
ISET
Charge Current Setting and System Loop Compensation Pin. Connect a
resistor from this pin to ground to set the charge current.
4
VC
Control Signal of the Inner Loop of the Current Mode PWM. A capacitor of at
least 0.1F with a serial resistor to GND filters out the current ripple.
5
NTC
Input for an external NTC thermistor for battery temperature monitoring.
6
VFB
Battery Voltage Feedback. Using an external resistor divider to set battery full
charge voltage.
7
VHH
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 1.8V.
8
BATT
Battery Voltage Sensing Input. A 10F or larger X5R ceramic capacitor is
recommended for filtering charge current ripple and stability purpose.
9
SNSL
Negative Terminal for Sensing Charge Current.
10
SNSH
Positive Terminal for Sensing Charge Current.
11
PGND
Power Ground.
12
SW
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.
13
HSD
Drain of Internal High-Side Power N-MOSFET Switch. Connect a low ESR
capacitor of 10F or higher from this pin to ground for good bypass.
14
BOOT
Bootstrap Supply for the High-Side Power Switch Gate Driver and Control
Circuitry. In normal operation, VBOOT ≈ VSW + 5V.
15
VIN
Input Power Supply. Connect a low ESR capacitor of 10F or higher from this
pin to ground for good bypass.
16
V5V
Output of Internal 5V LDO. Connect a 1F ceramic capacitor from this pin to
GND for stability.
17
(Exposed Pad)
GND
Exposed Pad. Connect the exposed pad to PGND.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9535A-03
June 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
3
RT9535A
Function Block Diagram
R1
200k
NTC
VIN
THERMISTOR
REFERENCE
1.4V
C3
EN
0.5uA
5V
SD
UVLO
VIN
V5V
LDO
+
VIN
VREF
2.5V
C2
BATT
0.4V
UVLO
3.9V
ICHG
VHH
SLOP COMP
OSCILLATOR
SNSL
BOOT
R2
SNSH
CA
ICHG
PWM
C1
VREF
2.5V
IVA
VFB
VREF
2.5V
EA
HSD
S
R
SW
VA
1.3V
GND
Soft-Start
COUNTER
ISET
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
4
SS
VC
PGND
is a registered trademark of Richtek Technology Corporation.
DS9535A-03
June 2015
RT9535A
Operation
The RT9535A is a current mode PWM step-down
switching charger controller. The battery DC charge
current is programmed by a resistor R4 at the ISET pin
and the ratio of sense resistor RS2 over RS1 in the
typical application circuit. Amplifier CA converts the
charge current through RS1 to a much lower sampled
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 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 current
mode inner loop. An internal LDO generates a 5V to
power high-side MOSFET gate driver. For batteries like
lithium that require both constant current and constant
voltage charging, the 0.5% 2.5V reference and the
voltage amplifier VA reduce the charge current when
battery voltage reaches the normal charge voltage level.
For NiMH and NiCd, VA can be used for over-voltage
protection.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9535A-03
June 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
RT9535A
Absolute Maximum Ratings
(Note 1)
VHH, BOOT to GND -------------------------------------------------------------------------------------------------- 0.3V to 36V
VIN, EN, SW, HSD to GND ----------------------------------------------------------------------------------------- 0.3V to 30V
ISET, VC, VFB, V5V SS, NTC to GND -------------------------------------------------------------------------- 0.3V to 6V
BATT SNSH, SNSL to GND ---------------------------------------------------------------------------------------- 0.3V to 28V
Power Dissipation, PD @ TA = 25C
WQFN-16L 4x4 -------------------------------------------------------------------------------------------------------- 3.5W
Package Thermal Resistance
(Note 2)
WQFN-16L 4x4, JA -------------------------------------------------------------------------------------------------- 28.5C/W
WQFN-16L 4x4, JC -------------------------------------------------------------------------------------------------- 7C/W
Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------- 260C
Junction Temperature ------------------------------------------------------------------------------------------------ 150C
Storage Temperature Range --------------------------------------------------------------------------------------- 65C to 150C
ESD Susceptibility
HBM (Human Body Model) ----------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ------------------------------------------------------------------------------------------------- 200V
(Note 3)
Recommended Operating Conditions
(Note 4)
Supply Input Voltage ------------------------------------------------------------------------------------------------- 4.5V to 28V
Battery Voltage, VBAT ----------------------------------------------------------------------------------------------- 2.5V to 22V
Ambient Temperature Range--------------------------------------------------------------------------------------- 40C to 85C
Junction Temperature Range -------------------------------------------------------------------------------------- 40C to 125C
Electrical Characteristics
(VIN = VBAT + 3V, VBAT is the full charge voltage, pull-up EN to VIN with 100k resistor, TA = 25C, 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, VEN = 0
VBATT = VSW = VSNSH =
VSNSL = 20V
--
--
10
A
VIN Under-Voltage Lockout
VIN Under-Voltage Lockout
Hysteresis
Reference
VUVLO
3.6
3.8
4.3
V
--
300
--
mV
Reference Voltage
VFB
2.486
2.5
2.514
V
FB Bias current
IFB
--
--
0.1
A
VUVLO_HYS
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
6
VFB = 2.5V
is a registered trademark of Richtek Technology Corporation.
DS9535A-03
June 2015
RT9535A
Parameter
Charge Current
Full-Scale Charge Current
Sense Voltage
Symbol
VICHG
Test Conditions
Min
Typ
Max
Unit
Measure the Voltage
Drop Across RS1
95
100
105
mV
−1
--
--
mA
ISET Output Current
IISET
SNSL Bias Current
ISNSL
No Charge Current
−36
−12
−6
A
SNSH Bias Current
ISNSH
No Charge Current
−36
−12
−6
A
--
--
2
V
Battery Voltage
VHH Minimum Voltage with
Respect to BATT
VIN Minimum Voltage with
Respect to BATT
VHH Input Current
VHH
BATT Bias Current
IBATT
VC Pin Current
IVC
VDROP
(Note 5)
--
0.3
0.4
V
IVHH
VHH = 28V
VEN = 0, VBATT = VSW =
VSNSH = VSNSL = 20V
40
95
150
A
--
--
10
A
VVC = 0V
−25
−15
−1
A
Switch Characteristics
Switching Frequency
High-Side Switch
On-Resistance
High-Side Switch leakage
Current
fOSC
430
500
545
kHz
RON
--
150
--
m
IHSD
VHSD = 28V, VEN = 0V
--
--
10
A
BOOT Leakage Current
IBOOT
VBOOT = 30V, VEN = 0V
(Note 5)
--
1
--
A
VVC = 0V
95
--
--
%
VSW = 28V, VEN = 0V
--
--
10
A
50mA Load at V5V,
VVC = 0V
4
5
6
V
Maximum Duty
SW Leakage Current
ILKGL
Regulator and Logic Characteristics
LDO Output Voltage
EN Input Voltage
VLDO
Logic-High
VENH
2.5
--
--
Logic-Low
VENL
--
--
0.6
--
--
10
A
1.5
3.3
6
A
73.5%
VV5V
31%
VV5V
0.2%
Vv5v
75%
VV5V
32.5%
VV5V
1.7%
Vv5v
76.5%
VV5V
34%
VV5V
3.2%
Vv5v
--
2
10
A
EN Input Current
IEN
Soft-Start Sourcing Current
ISS
0V ≤ VEN ≤ 5V
V
Thermal Comparator and Protection
NTC Threshold, Cold
VCOLD
NTC Threshold, Hot
VHOT
NTC Disable Threshold
VDISNTC
NTC Bias Current
Thermal Shutdown
Temperature
Thermal Shutdown Hysteresis
INTC
June 2015
V
V
V
TSD
(Note 5)
--
160
--
°C
TSD
(Note 5)
--
30
--
°C
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9535A-03
NTC Voltage Rising,
1% Hysteresis
NTC Voltage Rising,
1% Hysteresis
NTC Voltage Rising,
1% Hysteresis
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
7
RT9535A
Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for
stress ratings. 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 for extended
periods may remain possibility to affect device reliability.
Note 2. JA is measured at TA = 25C 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.
Note 5. Guaranteed by design, not subjected to production test.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
8
is a registered trademark of Richtek Technology Corporation.
DS9535A-03
June 2015
RT9535A
Typical Application Circuit
D4
PMEG4020
VIN
C1
10μF
R2
10
R1
100k
1
15
HSD
EN
C3
(Optional)
R4
10k
R5
1k
C4
3.3nF
VIN
3
ISET
4
VC
2 SS
V5V
GND
SW
PGND
VHH
7
VHH
R7
100k
R6
100k
BOOT
6 VFB
D2
16
NTC 5
C5
0.01μF
17 (Exposed Pad)
C9
(Optional)
VFB
C2
10μF x 2
RT9535A
CIN
1μF
R3
(Optional)
13
SNSH
14
12
11
C7
1μF
RNTC
D3
To RS3
VHH
C6
0.1μF
R8
10
C8
0.1μF
D1
PMEG2030
L1
10μH
RS3
402
RS1
0.1
RS2
402
VBATT
CBATT
22μF
10
RF2
390k
To VFB
TVS
RF1
100k
9
SNSL
8
BATT
Note :
(1). For application with removable battery, a TVS with appropriate rating is required as shown above.
(2). VIN = 15V to 28V, 3 – cell, ICHARGE = 1A
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9535A-03
June 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
9
RT9535A
Typical Operating Characteristics
Efficiency vs. Charge Current
100
95
95
Efficiency (%)
Efficiency (%)
Efficiency vs. Supply Voltage
100
90
85
1 Cell : VBATT
2 Cell : VBATT
3 Cell : VBATT
4 Cell : VBATT
5 Cell : VBATT
80
75
= 4V
= 8V
= 12V
= 16V
= 20V
90
85
1 Cell : VIN = 12V, VBATT
2 Cell : VIN = 24V, VBATT
3 Cell : VIN = 24V, VBATT
4 Cell : VIN = 24V, VBATT
5 Cell : VIN = 24V, VBATT
80
75
IBATT = 1A
70
70
0
5
10
15
20
25
0.5
30
1
1.5
2
2.5
Charge Current (A)
Supply Voltage (V)
Charge Current vs. Supply Voltage
Supply Current vs. Temperature
1.20
1.2
1.12
1.08
1.04
= 4V
= 8V
= 12V
= 16V
= 20V
1.0
Supply Current (mA)
1 Cell : VIN = 12V, VBATT
2 Cell : VIN = 24V, VBATT
3 Cell : VIN = 24V, VBATT
4 Cell : VIN = 24V, VBATT
5 Cell : VIN = 24V, VBATT
1.16
Charge Current (A)
= 4V
= 8V
= 12V
= 16V
= 20V
1.00
0.96
0.92
0.88
0.8
0.6
0.4
VIN = 28V
VIN = 12V
0.2
0.84
0.80
0.0
0
10
20
30
-50
-25
Supply Voltage (V)
0
25
50
75
100
125
Temperature (℃)
Shutdown Current vs. Temperature
V5V Voltage vs. Temperature
45
5.00
4.95
35
V5V Voltage (V)
Shutdown Current (A)
40
30
25
20
VIN = 28V
VIN = 12V
15
10
4.90
4.85
4.80
4.75
5
VIN = 12V, IV5V = 40mA
0
4.70
-50
-25
0
25
50
75
100
Temperature (℃)
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
10
125
-50
-25
0
25
50
75
100
125
Temperature (℃)
is a registered trademark of Richtek Technology Corporation.
DS9535A-03
June 2015
RT9535A
VICHG vs. Temperature
VFB Voltage vs. Temperature
110
2.55
108
106
2.53
VFB Voltage (V)
VICHG (mV)
104
102
100
98
96
94
92
90
-50
-25
0
25
50
2.51
2.49
VIN = 4.5V
VIN = 12V
VIN = 28V
2.47
100
2.45
75
125
VIN = 4.5V
VIN = 12V
VIN = 28V
-50
Temperature (°C)
0
25
50
75
100
125
Temperature (°C)
BATT Bias Current vs.Temperature
Switching Frequency vs. Supply Voltage
14
510
12
505
BATT Bias Current (A)
Switching Frequency (kHz)
-25
500
495
490
485
10
8
6
4
2
0
480
0
5
10
15
20
25
30
-50
Charge Enable and Disable
0
25
50
75
100
125
Adapter Insert and Remove
VBATT
(2V/Div)
SW-GND
(10V/Div)
VBATT
(2V/Div)
SW-GND
(10V/Div)
EN
(2V/Div)
VIN
(5V/Div)
IBATT
(500mA/Div)
VIN = 12V, VBATT = 4V, IBATT = 1A
Time (25ms/Div)
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9535A-03
-25
Temperature (℃)
Supply Voltage (V)
June 2015
IBATT
(500mA/Div)
VIN = 12V, VBATT = 4V, IBATT = 1A
Time (25ms/Div)
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
RT9535A
Charge Enable
Charge Disable
VBATT
(2V/Div)
VBATT
(2V/Div)
SW-GND
(10V/Div)
SW-GND
(10V/Div)
EN
(2V/Div)
EN
(2V/Div)
IBATT
(500mA/Div)
VIN = 12V, VBATT = 4V, IBATT = 1A
IBATT
(500mA/Div)
Time (10ms/Div)
Time (10ms/Div)
Switching
VBATT
(5V/Div)
VBATT
(5V/Div)
IL
(500mA/Div)
VIN = 12V, VBATT = 4V, IBATT = 1A
Time (1s/Div)
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
12
BATT to GND Short Response
IIN
(1A/Div)
IBATT
(1A/Div)
IL
(500mA/Div)
SW-GND
(10V/Div)
VIN = 12V, VBATT = 4V, IBATT = 1A
SW-GND
(10V/Div)
VIN = 12V, VBATT = 4V, IBATT = 1A
Time (10ms/Div)
is a registered trademark of Richtek Technology Corporation.
DS9535A-03
June 2015
RT9535A
Application Information
Input and Output Capacitors
and the battery impedance. If the ESR of COUT is 0.2
In the typical application circuit, the input capacitor (C2)
and the battery impedance is raised to 4 with a bead
is assumed to absorb all input switching ripple current
or inductor, only 5% of the ripple current will flow in the
in the converter, so it must have adequate ripple
battery.
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
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
tradeoff is to choose the inductor so that the current
ripple is approximately 30% to 50% of the full-scale
charge current. The inductor value is calculated as :
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 20F capacitance is suggested for
typical of 2A charging current.
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 12H. So
choose L1 to be 10H which is close to 12H.
The output capacitor (CBATT) is also assumed to
Soft-Start and Under-Voltage Lockout
absorb output switching current ripple. The general
The soft-start is controlled by the voltage rise time at
formula for capacitor current is :
SS pin. There are internal soft-start and external
VBATT
VBATT 1VVIN
IRMSCB =
2 3 L1 fosc
soft-start in the RT9535A. With a 0.01F capacitor,
For example, VVIN = 19V, VBATT = 8.4V, L1 = 10H,
value in less than 20ms. The capacitor can be
and f OSC = 500kHz, IRMS = 0.15A.
increased if longer input start-up times are needed.
EMI considerations usually make it desirable to
For the RT9535A, it provides Under-Voltage Lockout
minimize ripple current in the battery leads. Beads or
(UVLO) protection. If 5V5LDO output voltage is lower
inductors may be added to increase battery impedance
than 3.5V, high-side internal power MOSFET. This will
at the 500kHz switching frequency. Switching ripple
protect the adapter from entering a quasi “latch” state
current splits between the battery and the output
where the adapter output stays in a current limited state
capacitor depending on the ESR of the output capacitor
at reduced output voltage.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9535A-03
June 2015
time to reach full charge current is about 20ms and it is
assumed that input voltage to the charger will reach full
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
13
RT9535A
Full-Scale Charge Current Programming
The basic formula for full-scale charge current is (see
RF2
VBATT = 2.5 1+
RF1
Block Diagram) :
where RF2 is connected from VFB to the battery and
VREF
IBATT =
R4
RF1 is connected from VFB to GND.
RS2
RS1
Charging
Where R4 is the total resistance from ISET pin to
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
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.
= 50m. This limits RS1 power to 0.2W. Let R4 = 10k,
Dropout Operation
then :
RS2 = RS3 =
IBATT R4 RS1 2A 10k 0.05
=
= 400Ω
VREF
2.5V
The RT9535A can charge the battery even when VIN
goes as low as 2V above the combined voltages of the
Note that for charge current accuracy and noise
battery and the drops on the sense resistor as well as
immunity, 100mV full scale level across the sense
parasitic wiring. This low VIN sometimes forces 100%
resistor RS1 is required. Consequently, both RS2 and
duty cycle and high-side power switch stays on for
RS3 should be 402. The R4 should be set to between
many switching cycles. While high-side power switch
5k and 15k for the best operation.
stays on, the voltage VBOOT across the capacitor C8
It is critical to have a good Kelvin connection on the
drops down slowly because the current sink at BOOT
current sense resistor RS1 to minimize stray resistive
pin. C8 needs to be recharged before VBOOT drops too
and inductive pickup. RS1 should have low parasitic
low to keep the topside switch on.
inductance (typical 3nH or less). The layout path from
A unique design allows the RT9535A to operate under
RS2 and RS3 to RS1 should be kept away from the fast
these conditions. If SW pin voltage keeps larger than
switching SW node. A 1nF ceramic capacitor can be
1.3V for 32 oscillation periods, high-side power
used across SNSH and SNSL and be kept away from
MOSFET will be turned off and an internal MOSFET
the fast switching SW node.
will be turned on to pull SW pin down. This function
Battery Voltage Regulation
The RT9535A uses high-accuracy voltage bandgap
refreshes VBOOT voltage to a higher value. It is
important to use 0.1F to hold VBOOT up for a sufficient
amount of time.
and regulator for the high charging-voltage accuracy.
The charge voltage is programmed via a resistor
Shutdown
divider from the battery to ground, with the midpoint
When adapter power is removed, VIN will drift down.
tied to the VFB pin. The voltage at the VFB pin is
As soon as VIN goes down to 0.1V above VBATT, the
regulated to 2.5V, giving the following equation for the
RT9535A will go into sleep mode drawing only ~10A
regulation voltage:
from the battery. There are two suggest
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
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
14
is a registered trademark of Richtek Technology Corporation.
DS9535A-03
June 2015
RT9535A
chip. Pulling the VC pin low will only stop switching and
5V5LDO stays active. 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
Note that the RT9535A 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 high-side internal
N-MOSFET. A small diode from the EN pin to VBATT
will shut down switching and protect the charger.
Temperature Qualification
The controller RT9535A continuously monitors battery
temperature by measuring the voltage between the
NTC pin and GND. A negative temperature coefficient
Assuming a 103AT NTC thermistor on the battery pack
as shown in the below, the values of RT1 and RT2 can
be determined by using the following equations :
1
1
VV5V RTHCOLD RTHHOT
V
V
COLD HOT
RT2 =
VV5V
VV5V
RTHHOT
-1 -RTHHOT
-1
V
HOT
VCOLD
VV5V
-1
VCOLD
RT1 =
1
1
+
RT2 RTHCOLD
thermistor (NTC) and an external voltage divider
typically generate this voltage. The controller compares
V5V
this voltage against its internal thresholds to determine
if charging is allowed. To initiate a charge cycle, the
battery temperature must be within the VCOLD. If
RT9535A
RT1
NTC
battery temperature is outside of this range, the
RT2
controller suspends charge and the safety timer and
waits until the battery temperature is within the VCOLD
RTH
103AT
TS Resistor Network
to VHOT range. During the charge cycle, the battery
temperature must be within the VCOLD and VDISNTC
thresholds. If the battery temperature is outside of this
Where RTHCOLD and RTHHOT which have defined in the
spec of the 103AT NTC thermistor.
range, the controller suspends charge and waits until
Thermal Considerations
the battery temperature is within the VCOLD to VHOT
For continuous operation, do not exceed absolute
range. The controller suspends charge by turning off
maximum junction temperature. The maximum power
the PWM charge MOSFETs.
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
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9535A-03
June 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
15
RT9535A
where TJ(MAX) is the maximum junction temperature,
TA is the ambient temperature, and JA is the junction to
ambient thermal resistance.
For recommended operating condition specifications,
the maximum junction temperature is 125C. The
junction to ambient thermal resistance, JA, is layout
dependent. For WQFN-16L 4x4 package, the thermal
resistance, JA, is 28.5C/W on a standard JEDEC
51-7 four-layer thermal test board. The maximum
power dissipation at TA = 25C can be calculated by
the following formula :
PD(MAX) = (125C 25C) / (28.5C/W) = 3.5W for
WQFN-16L 4x4 package
The maximum power dissipation depends on the
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
Maximum Power Dissipation (W)1
temperature on the maximum power dissipation.
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.
www.richtek.com
16
is a registered trademark of Richtek Technology Corporation.
DS9535A-03
June 2015
RT9535A
Layout Consideration
dissipation can go as high as 0.5W. Expanded traces
Switch rise and fall times are under 20ns for maximum
should be used for the diode leads for low thermal
efficiency. To prevent radiation, the SW pin, the rectifier
resistance. Another large heat dissipating device is
Schottky diode D1 and input bypass capacitor leads
probably the inductor. The fast switching high current
should be kept as short as possible. A ground plane
ground path including the MOSFETs, D1 and input
should be used under the switching circuitry to prevent
bypass capacitor C2 should be kept very short. Another
inter-plane coupling and to act as a thermal spreading
smaller input bypass (1F ceramic or larger paralleled
path. Note that the rectifier Schottky diode D1 is
with CIN) should be placed to VIN pin and GND pin as
probably the most heat dissipating device in the
close as possible.
charging system. The voltage drop on a 2A Schottky
diode can be 0.5V. With 50% duty cycle, the power
Input capacitor and C7 must
be placed as close to
the IC as possible.
Place these power components as
close to the SW pin as possible.
Input Power, VIN
D4
GND
C7
SW
C1
CIN
C8
D2
R4
C4
VC
R5
D1
BOOT
2
11
3
GND 17
4
5
6
7
L1
PGND
10 SNSH
RS3
SNSL
RS2
9
8
CBATT
VBATT
RS1
BATT
12 SW
RSL
1
BATT
ISET
R3
14 13
VHH
C3
SS
15
VFB
C5
16
NTC
VIN
EN
RSH
VHH
R1
VIN
V5V
D3
C2
HSD
RB
BOOT
RSH
RSL
C6
Locate the compensation components to
the SS/VC/ISET pin as close as possible.
NTC
C9
R6
R7
GND
RF2
V5V
BATT
RF1
C9 must be placed as close
to the IC as possible.
Locate the compensation components to
the NTC/VFB pin as close as possible.
Figure 2. PCB Layout Guide
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
DS9535A-03
June 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
17
RT9535A
Outline Dimension
Symbol
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
0.250
0.380
0.010
0.015
D
3.950
4.050
0.156
0.159
D2
2.000
2.450
0.079
0.096
E
3.950
4.050
0.156
0.159
E2
2.000
2.450
0.079
0.096
e
L
0.650
0.500
0.026
0.600
0.020
0.024
W-Type 16L 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.
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
18
is a registered trademark of Richtek Technology Corporation.
DS9535A-03
June 2015
工商网监
湘ICP备2023018690号
