MP2635
The Future of Analog IC Technology
2.0A Single Cell Switch Mode Battery Charger
with Power Path Management (PPM) and
1.5A System Boost Current
DESCRIPTION
FEATURES
The MP2635 is a highly-integrated, flexible,
switch-mode battery charge management and
system power path management device for a
single-cell Li-ion and Li-Polymer battery used in
a wide range of portable applications.
The MP2635 has two operating modes—charge
mode and boost mode—to allow management
of system and battery power based on the state
of the input.
When input power is present, the device
operates in charge mode. It automatically
detects the battery voltage and charges the
battery in the three phases: trickle current,
constant current and constant voltage. Other
features include charge termination and autorecharge. This device also integrates both input
current limit and input voltage regulation in
order to manage input power and meet the
priority of the system power demand.
In the absence of an input source, the MP2635
switches to boost mode through the MODE pin
to power the SYS pins from the battery. The
OLIM pin programs the output current limit in
boost mode. The MP2635 also allows an output
short-circuit thanks to an output disconnect
feature, and can auto-recover when the short
circuit fault is removed.
The MP2635 provides full operating status
indication to distinguish charge mode from
boost mode.
4.5V-to-6V Operating Input Voltage Range
Power Management Function Integrated
Input-Current Limit and Input-Voltage
Regulation
Up to 2A Programmable Charge Current
Trickle-Charge Function
Selectable Charge Voltage with 0.5%
Accuracy: 3.6V/4.2V(MP2635) or
4.35V/4.2V(MP2635B)
Negative Temperature Coefficient Pin for
Battery Temperature Monitoring
Programmable Timer Back-Up Protection
Thermal Regulation and Thermal Shutdown
Internal Battery Reverse Leakage Blocking
Reverse Boost Operation Mode for System
Power
Up to 91% 5V Boost Mode Efficiency @ 1A
Programmable Output Current Limit for
Boost Mode
Integrated Short Circuit Protection for Boost
Mode
APPLICATIONS
Sub-Battery Applications
Power-Bank Applications for Smart-Phone
Tablet and Other Portable Devices
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status, please visit MPS website under Products, Quality Assurance page.
“MPS” and “The Future of Analog IC Technology” are registered trademarks of
Monolithic Power Systems, Inc.
The
MP2635
achieves
low
EMI/EMC
performance with well-controlled switching
edges.
To guarantee safe operation, the MP2635 limits
the die temperature to a preset value 120oC.
Other safety features include input over-voltage
protection, battery over-voltage protection,
thermal
shutdown,
battery
temperature
monitoring, and a programmable timer to
prevent prolonged charging of a dead battery.
The MP2635 has two battery full options.
MP2635: 4.2V/3.6V; MP2635B: 4.35V/4.2V.
MP2635 Rev. 1.08
4/27/2016
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1
MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
TYPICAL APPLICATION
Table 1: Operation Mode
__________
Power Source
ACOK
EN
High
MODE
Charge Mode, Enable Charging
0.8V VBATT_TC
Autorecharge
Figure 8: EN Start-Up Time Flow in Charge Mode
MP2635 Rev. 1.08
4/27/2016
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20
MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
START UP TIME FLOW IN BOOST MODE
Condition: VIN = 0V, Mode = 5V, /Boost is always pulled up to an external constant 5V.
2.5V
2.9V
VBATT
0V
0V
VCC follows
VBATT
VCC follows VSYS
2.2V
VCC
MODE
Band
Gap
5V
BOOST 0V
1.2ms
Boost
SS
VSYS
Down
Mode
0V
VSYS>VBATT+300mV
Figure 9: Battery Power Start-Up Time Flow in Boost Mode
MP2635 Rev. 1.08
4/27/2016
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21
MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
START UP TIME FLOW IN BOOST MODE
Condition: VIN = 0V, /Boost is always pulled up to an external constant 5V.
VBATT
2.9V
VCC follows VSYS
VCC follows VBATT
VCC
2.2V
5V
0V
MODE
5V
Band
Gap
0V
5V
BOOST
0V
1.2ms
Boost
SS
VSYS
Down
Mode
0V
VSYS>VBATT+300mV
Figure 10: Mode Start-Up Time Flow in Boost Mode
MP2635 Rev. 1.08
4/27/2016
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22
MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
OPERATION
INTRODUCTION
CC>>>CV
Threshold
The MP2635 is a highly-integrated, synchronous,
switching charger with bi-directional operation for
a boost function that can step-up the battery
voltage to power the system. Depending on the
VIN value, it operates in one of three modes:
charge mode, boost mode and sleep mode. In
charge mode, the MP2635 supports a precision
Li-ion or Li-polymer charging system for singlecell applications. In boost mode, MP2635 boosts
the battery voltage to VSYS to power highervoltage systems. In sleep mode, the MP2635
stops charging or boosting and operates at a low
current from the input or the battery to reduce
power consumption when the IC isn’t operating.
The MP2635 monitors VIN to allow smooth
transition between different modes of operation.
ChargeCC
In charge mode, the MP2635 has five control
loops to regulate the input current, input voltage,
charge current, charge voltage, and device
junction temperature. It charges the battery in
three phases: trickle current (TC), constant
current (CC), and constant voltage (CV). While
charging, all four loops are active but only one
determines the IC behavior. Figure 11(a) shows
a typical battery charge profile. The charger stays
in TC charge mode until the battery voltage
reaches a TC-to-CC threshold. Otherwise the
charger enters CC charge mode. When the
battery voltage rises to the CV-mode threshold,
the charger operates in constant voltage mode.
Figure 11(b) shows a typical charge profile when
the input-current-limit loop dominates during the
CC charge mode, and in this case the charge
current exceeds the input current, resulting in
faster charging than a traditional linear solution
that is well-suited for USB applications.
MP2635 Rev. 1.08
4/27/2016
VBAT
TC>>>CC
Threshold
Trickle
Charge
Current
Trickle charge
CC charge
CV charge
Charge Full
a) Without input current limit
Constant
Charge
Current
CC>>>CV
Threshold
ICHG
Input
Current
Limit
VBAT
TC>>>CC
Threshold
Trickle
Charge
Current
Trickle charge
CHARGE MODE OPERATION
Charge
Cycle
(Trickle
ChargeCV Charge)
ICHG
Constant
Charge
Current
CC charge
CV charge
Charge Full
b) With input current limit
Figure 11: Typical Battery Charge Profile
Auto-Recharge
Once the battery charge cycle completes, the
charger remains off. During this process, the
system load may consume battery power, or the
battery may self discharge. To ensure the battery
will not go into depletion, a new charge cycle
automatically begins when the battery voltage
falls below the auto-recharge threshold and the
input power is present. The timer resets when the
auto-recharge cycle begins.
During the off state after the battery is fully
charged, if the input power re-starts or the EN
signal refreshes, the charge cycle will start and
the timer will reset no matter what the battery
voltage is.
Battery Over-Voltage Protection
The MP2635 has battery over-voltage protection.
If the battery voltage exceeds the battery overvoltage threshold, (103.3% of the battery-full
voltage), charging is disabled. Under this
condition, an internal current source draws a
current from the BATT pin to decrease the
battery voltage and protect the battery.
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23
MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
Input Over-Current Protection
Timer Operation in Charge Mode
The MP2635 uses an internal timer to terminate
the charging. The timer remains active during the
charging process. An external capacitor between
TMR and GND programs the charge cycle
duration.
If charging remains in TC mode beyond the
trickle-charge time, τTRICKLE_TMR, charging will
terminate. The following determines the length of
the trickle-charge period:
TRICKLE _ TMR 60 min s
CTMR (F)
1A
(1)
0.1F
ICHG ( A )
The maximum total charge time is:
CTMR (F)
1A
(2)
0.1F
ICHG ( A )
Negative Temperature Coefficient (NTC) Input
TOTAL _ TMR 6Hours
for Battery Temperature Monitoring
The MP2635 has a built-in NTC resistance
window comparator, which allows the MP2635 to
monitor the battery temperature via the batteryintegrated thermistor. Connect an appropriate
resistor from VSYS to the NTC pin and connect the
thermistor from the NTC pin to GND. The resistor
divider determines the NTC voltage depending
on the battery temperature. If the NTC voltage
falls outside of the NTC window, the MP2635
stops charging. The charger will then restart if the
temperature goes back into NTC window range.
Input-Current Limiting in Charge Mode
The MP2635 has a dedicated pin that programs
the input-current limit. The current at ILIM is a
fraction of the input current; the voltage at ILIM
indicates the average input current of the
switching regulator as determined by the resistor
value between ILIM and GND. As the input
current approaches the programmed input
current limit, charge current is reduced to allow
priority to system power.
Use the following equation to determine the input
current limit threshold,
IILIM
MP2635 Rev. 1.08
4/27/2016
40.5(k)
(A)
R ILIM (k)
The MP2635 features input over-current
protection (OCP): when the input current
exceeds 3A, Q2 is controlled linearly to regulate
the current. If the current still exceeds 3A after a
120µs blanking time, Q2 will turn off. A fast off
function turns off Q2 quickly when the input
current exceeds 7A to protect both Q1 and Q2.
Input Voltage Regulation in Charge Mode
In charge mode, if the input power source is not
sufficient to support both the charge current and
system load current, the input voltage will
decrease. As the input voltage approaches the
programmed input voltage regulation value,
charge current is reduced to allow priority of
system power and maintain the input voltage
avoid dropping further.
The input voltage can be regulated by a resistor
divider from IN pin to REG pin to AGND
according to the following expression:
R5
(4)
(V)
R3 R5
Where the VREG is the internal voltage reference,
1.2V.
VREG VIN _ R
Setting the Charge Current
The external sense resistors, RS1 and RISET,
program the battery charge current, ICHG. Select
RISET based on RS1:
ICHG (A)=
70(kΩ)
40(mV)
RISET (kΩ) RS1(mΩ)
(5)
Where the 40mV is the charge current limiting
reference.
Battery Short Protection
The MP2635 has two current limit thresholds. CC
and CV modes have a peak current limit
threshold of 3.6A, while TC mode has a current
limit threshold of 1.5A. Therefore, the current limit
threshold decreases to 1.5A when the battery
voltage drops below the TC threshold. Moreover,
the switching frequency also decreases when the
BATT voltage drops to 40% of the charge-full
voltage.
(3)
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24
MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
Thermal Foldback Function
The MP2635 implements thermal protection to
prevent thermal damage to the IC and the
surrounding components. An internal thermal
sense and feedback loop automatically
decreases the programmed charge current when
the die temperature reaches 120°C. This function
is called the charge-current-thermal foldback. Not
only does this function protect against thermal
damage, it can also set the charge current based
on requirements rather than worst-case
conditions while ensuring safe operation.
Furthermore, the part includes thermal shutdown
protection where the ceases charging if the
junction temperature rises to 150°C.
Full-Operation Indication
The MP2635 integrates indicators for
following conditions as shown in Table2.
the
Table 2: Indicator for Each Operation Mode
----------------
Operation
ACOK
In Charging
Charge Mode
MP2635 Rev. 1.08
4/27/2016
End of Charge,
charging disabled
NTC Fault, Timer
Out
------------
CHG
-------------------
BOOST
Low
Low
High
High
Blinking
Boost Mode
High
High
Low
Sleep Mode, VCC absent
High
High
High
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25
MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
BOOST MODE OPERATION
Low-Voltage Start-Up
The minimum battery voltage required to start up
the circuit in boost mode is 2.9V. Initially, when
VSYS < VBATT, the MP2635 works in down mode.
In this mode, the synchronous P-MOSFET stops
switching and its gate connects to VBATT statically.
The P-MOSFET keeps off as long as the voltage
across the parasitic CDS (VSW) is lower than VBATT.
When the voltage across CDS exceeds VBATT, the
synchronous P-MOSFET enters a linear mode
allowing the inductor current to decrease and
flowing into the SYS pin. Once VSYS exceeds
VBATT, the P-MOSFET gate is released and
normal closed-loop PWM operation is initiated. In
boost mode, the battery voltage can drop to as
low as 2.5V without affecting circuit operation.
SYS Disconnect and Inrush Limiting
The MP2635 allows for true output disconnect by
eliminating body diode conduction of the internal
P-MOSFET rectifier. VSYS can go to 0V during
shutdown, drawing no current from the input
source. It also allows for inrush current limiting at
start-up, minimizing surge currents from the input
supply. To optimize the benefits of output
disconnect, avoid connecting an external
Schottky diode between the SW and SYS pins.
Board layout is extremely critical to minimize
voltage overshoot at the SW pin due to stray
inductance. Keep the output filter capacitor as
close as possible to the SYS pin and use very
low ESR/ESL ceramic capacitors tied to a good
ground plane.
Boost Output Voltage
In the boost mode, the MP2635 programs the
output voltage via the external resistor divider at
FB pin, and provides built-in output over-voltage
protection (OVP) to protect the device and other
components against damage when VSYS goes
beyond 6V. Should output over-voltage occur,
the MP2635 turns off the boost converter. Once
VSYS drops to a normal level, the boost converter
restarts again as long as the MODE pin remains
in active status.
MP2635 Rev. 1.08
4/27/2016
Boost Output-Current Limiting
The MP2635 integrates a programmable output
current limit function in boost mode. If the boost
output current exceeds this programmable limit
threshold, the output current will be limited at this
level and the SYS voltage will start to drop down.
The OLIM pin programs the current limit
threshold up to 1.5A as per the following
equation:
70( k ) 40(mV ) 1.6
(6)
ROLIM (k ) RS1(m )
Where the 40mV is the charge current limiting
reference.
IOLIM ( A)
SYS Output Over-Current Protection
The MP2635 integrates three-phase output overcurrent protection.
Phase one (boost mode): when the output
current exceeds the output current limit, the
output constant current loop controls the output
current, the output current remains at its limit of
IOLIM, and VSYS decreases.
Phase two (down mode): when VSYS drops below
VBATT+100mV and the output current loop
remains in control, the boost converter enters
down mode and shutdown after a 120μs blanking
time.
Phase three (short circuit mode): when VSYS
drops below 2V, the boost converter shuts down
immediately once the inductor current hits the
fold-back peak current limit of the low side NMOSFET. The boost converter can also recover
automatically after a 1ms deglitch period.
Thermal Shutdown Protection
The thermal shutdown protection is also active in
boost mode. Once the junction temperature rises
higher than 150°C, the MP2635 enters thermal
shutdown. It will not resume normal operation
until the junction temperature drops below 120°C
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26
MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
VPWIN VIN
APPLICATION INFORMATION
COMPONENT SELECTION
Setting the Charge Current in Charge Mode
In charge mode, both the external sense resistor,
RS1, and the resistor RISET connect to the ISET
pin to set the charge current (ICHG) of the MP2635
(see the Typical Application circuit).
Given ICHG and RS1, the regulation threshold,
VIREF, across this resistor is:
VIREF (mV ) RS1(m ) ICHG ( A )
(7)
70(k )
40(mV )
R ISET (k )
So, the RISET can be calculated as:
70(k )
RISET (k )
40(mV )
VIREF (mV )
(9)
Setting the Input Current Limiting in Charge
Mode
In charge mode, connect a resistor from the ILIM
pin to AGND to program the input current limit.
The relationship between the input current limit
and setting resistor is as following:
40.5
(k)
IIN _ LIM ( A )
If the voltage on PWIN is between 0.8V and
1.15V, the MP2635 works in the charge mode.
While the voltage on the PWIN pin is not in the
range of 0.8V to 1.15V and VIN > 2V, the
MP2635 works in the boost mode (see Table 1)).
For a wide operating range, use a maximum
input voltage of 6V as the upper threshold for a
voltage ratio of:
VPWIN 1.15
R6
(12)
VIN
6
R4 R6
R4
(8)
For example, for ICHG=2A, and RS1=50mΩ, thus:
VIREF=100mV, so RISET=28kΩ.
RILIM
(11)
With the given R6, R4 is then:
RISET sets VIREF as per the following equation:
VIREF (mV )
R6
(V)
R4 R6
(10)
Where RILIM must exceed 15kΩ, so that IIN_LIM is in
the range of 0A to 2.7A.
For most applications, use RILIM = 45kΩ
(IUSB_LIM=900mA) for USB3.0 mode, and use RLIM
= 81kΩ (IUSB_LIM=500mA) for USB2.0 mode.
Setting the Input Voltage Range for Different
Operation Modes
A resistive voltage divider from the input voltage
to PWIN pin determines the operating mode of
MP2635.
VIN VPWIN
R6
VPWIN
(13)
For a typical application, start with R6=5.1kΩ, R4
is 21.5kΩ.
Setting the Input Voltage Regulation in
Charge Mode
In charge mode, connect a resistor divider from
the IN pin to AGND with tapped to REG pin to
program the input voltage regulation.
R3 R5
(14)
VIN _ R VREG
(V)
R5
With the given R5, R3 is:
R3
VIN _ R VREG
(15)
R5( V )
VREG
For a preset input voltage regulation value, say
4.75V, start with R5=5.1kΩ, R3 is 15kΩ.
NTC Function in Charge Mode
Figure 12 shows that an internal resistor divider
sets the low temperature threshold (VTL) and high
temperature threshold (VTH) at 66%·VSYS and
35%·VSYS, respectively. For a given NTC
thermistor, select an appropriate RT1 and RT2 to
set the NTC window.
RT2 //RNTC_Cold
VTL
TL 66% (16)
VSYS RT1 RT2 //RNTC_Cold
RT2 //RNTC_Hot
VTH
TH 35% (17)
VSYS RT1 RT2 //RNTC_Hot
Where RNTC_Hot is the value of the NTC resistor at
the upper bound of its operating temperature
MP2635 Rev. 1.08
4/27/2016
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MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
range, and RNTC_Cold is its lower bound.
The two resistors, RT1 and RT2, independently
determine the upper and lower temperature limits.
This flexibility allows the MP2635 to operate with
most NTC resistors for different temperature
range requirements. Calculate RT1 and RT2 as
follows:
R T1
RT2
RNTC_Hot RNTC_Cold (TL TH)
TH TL (RNTC_Cold RNTC_Hot )
(TL TH) RNTC_Cold RNTC_Hot
(1 TL) TH RNTC_Cold - (1- TH) TL RNTC_Hot
(18)
(19)
For example, the NCP18XH103 thermistor has
the following electrical characteristic:
At 0°C, RNTC_Cold = 27.445kΩ;
At 50°C, RNTC_Hot = 4.1601kΩ.
Based on equation (18) and equation (19),
RT1=6.58kΩ and RT2 = 23.89kΩ are suitable for
an NTC window between 0°C and 50°C. Chose
approximate values: e.g., RT1=6.65kΩ and
RT2=23.7kΩ.
If no external NTC is available, connect RT1 and
RT2 to keep the voltage on the NTC pin within the
valid NTC window: e.g., RT1 = RT2 = 10kΩ.
R1 R2
VSYS 1.2V
(V)
1 .2 V
(21)
For example, for a 5V system voltage, R2 is
10kΩ, and R1 is 31.6kΩ.
Setting the Output Current Limit in Boost
Mode
In boost mode, connect a resistor from the OLIM
pin to AGND to program the output current limit.
The relationship between the output current limit
and setting resistor is as follows:
70(k ) 40(mV ) 1.6
(22)
ROLIM (k )
IOLIM ( A) RS1(m )
Where ROLIM is supposed to be greater than 59kΩ
with RS1=50mΩ, so that IOLIM can be
programmed up to 1.5A.
Selecting the Inductor
Inductor selection trades off between cost, size,
and efficiency. A lower inductance value
corresponds with smaller size, but results in
higher ripple currents, higher magnetic hysteretic
losses, and higher output capacitances. However,
a higher inductance value benefits from lower
ripple current and smaller output filter capacitors,
but results in higher inductor DC resistance (DCR)
loss.
Choose an inductor that does not saturate under
the worst-case load condition.
1. In Charge Mode
When MP2635 works in charge mode (as a
Buck Converter), estimate the required
inductance as:
V VBATT
V
(23)
L IN
BATT
IL _ MAX
VIN fS
Figure 12: NTC Function Block
Setting the System Voltage in Boost Mode
In the boost mode, the system voltage can be
regulated to the value customer required
between 4.2V to 6V by the resistor divider at FB
pin as R1 and R2 in the typical application circuit.
VSYS 1.2V
R1 R2
R2
(20)
Where 1.2V is the voltage reference of SYS. With
a typical value for R2, 10kΩ, R1 can be
determined by:
MP2635 Rev. 1.08
4/27/2016
Where VIN, VBATT, and fS are the typical input
voltage, the CC charge threshold, and the
switching frequency, respectively. ∆IL_MAX is
the maximum inductor ripple current, which is
usually designed at 30% of the CC charge
current.
With a typical 5V input voltage, 30% inductor
current ripple at the corner point between
trickle charge and CC charge (VBATT=3V), the
inductance is 1.67μH (for a 1.2MHz switching
frequency) and 3.33μH (for a 600kHz
switching frequency).
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MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
2. In Boost Mode
1. Charge Mode
When the MP2635 is in Boost mode (as a
Boost converter), the required inductance
value is calculated as:
V
( VSYS VBATT )
(24)
L BATT
VSYS fS IL _ MAX
IL _ MAX (30% 40%) IBATT (MAX )
(25)
V I
(26)
IBATT (MAX ) SYS SYS
VBATT
Where VBATT is the minimum battery voltage,
fSW is the switching frequency, and ∆IL_MAX is
the peak-to-peak inductor ripple current,
which is approximately 30% of the maximum
battery current IBATT(MAX), ISYS(MAX) is the
system current and η is the efficiency.
In the worst case where the battery voltage is
3V, a 30% inductor current ripple, and a
typical system voltage (VSYS=5V), the
inductance is 1.8μH (for the 1.2MHz
switching frequency) and 3.6µH (for the
600kHz switching frequency) when the
efficiency is 90%.
For best results, use an inductor with an
inductance of 1.8μH (for the 1.2MHz
switching frequency) and 3.6µH (for the
600kHz switching frequency) with a DC
current rating that is at least 30% higher than
the maximum charge current for applications.
For higher efficiency, minimize the inductor’s
DC resistance.
The capacitor CSYS acts as the input capacitor
of the buck converter in charge mode. The
input current ripple is:
VTC ( VIN _ MAX VTC )
(27)
IRMS _ MAX ISYS _ MAX
VIN _ MAX
2. Boost Mode
The capacitor, CSYS, is the output capacitor of
boost converter. CSYS keeps the system
voltage ripple small and ensures feedback
loop stability. The system current ripple is
given by:
VTC ( VSYS _ MAX VTC )
(28)
IRMS _ MAX ISYS _ MAX
VSYS _ MAX
Since the input voltage is passes to the system
directly, VIN_MAX=VSYS_MAX, both charge mode and
boost mode have the same system current ripple.
For ICC_MAX=2A, VTC=3V, VIN_MAX=6V, the
maximum ripple current is 1A. Select the system
capacitors base on the ripple-current temperature
rise not exceeding 10°C. For best results, use
ceramic capacitors with X5R or X7R dielectrics
with low ESR and small temperature coefficients.
For most applications, use a 22µF capacitor.
Selecting the Battery Capacitor CBATT
CBATT is in parallel with the battery to absorb the
high-frequency switching ripple current.
Selecting the Input Capacitor CIN
1. Charge Mode
The input capacitor CIN reduces both the surge
current drawn from the input and the switching
noise from the device. The input capacitor
impedance at the switching frequency should be
less than the input source impedance to prevent
high-frequency-switching current from passing to
the input. For best results, use ceramic
capacitors with X5R or X7R dielectrics because
of their low ESR and small temperature
coefficients. For most applications, a 22µF
capacitor will suffice.
The capacitor CBATT is the output capacitor of
the buck converter. The output voltage ripple
is then:
1 VBATT / VSYS
VBATT
(29)
rBATT
2
VBATT
8 C BATT fS L
Selecting the System Capacitor CSYS
Select CSYS based on the demand of the system
current ripple.
MP2635 Rev. 1.08
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MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
2. Boost Mode
The capacitor CBATT is the input capacitor of
the boost converter. The input voltage ripple
is the same as the output voltage ripple from
equation (29)
Both charge mode and boost mode have the
same battery voltage ripple. The capacitor CBATT
can be calculated as:
1 VTC / VSYS _ MAX
(30)
C BATT
2
8 rBATT _ MAX fS L
To guarantee the ±0.5% BATT voltage accuracy,
the maximum BATT voltage ripple must not
exceed 0.5% (e.g. 0.1%). The worst case occurs
at the minimum battery voltage of the CC charge
with the maximum input voltage.
For VSYS_MAX=6V, VCC_MIN=VTC=3V, L=3.9µH,
fS=600kHz or 1.2MHz, rBATT _ MAX 0.1% , CBATT is
board as possible. The exposed pad should
connect to as many GND copper planes in the
board as possible. This improves thermal
performance because the board conducts heat
away from the IC.
3) The PCB should have a ground plane
connected directly to the return of all components
through vias (e.g., two vias per capacitor for
power-stage capacitors, one via per capacitor for
small-signal components). If possible, add vias
inside the exposed pads for the IC. A star ground
design approach is typically used to keep circuit
block currents isolated (power-signal/controlsignal), which reduces noise-coupling and
ground-bounce issues. A single ground plane for
this design gives good results.
4) Place ISET, OLIM and ILIM resistors very
close to their respective IC pins.
22µF (for a 600kHz switching frequency) or 10µF
(for a 1.2MHz switching frequency).
A 22µF ceramic with X5R or X7R dielectrics
capacitor will be OK.
PCB Layout Guide
PCB layout is very important to meet specified
noise, efficiency and stability requirements. The
following design considerations can improve
circuit performance:
Top Layer
1) Route the power stage adjacent to their
grounds. Aim to minimize the high-side switching
node (SW, inductor) trace lengths in the highcurrent paths and the current sense resistor trace.
Keep the switching node short and away from all
small control signals, especially the feedback
network.
Place the input capacitor as close as possible to
the VIN and PGND pins. The local power input
capacitors, connected from the SYS to PGND,
must be placed as close as possible to the IC.
Bottom Layer
Figure 13: PCB Layout Guide
Place the output inductor close to the IC and
connect the output capacitor between the
inductor and PGND of the IC.
2) For high-current applications, the power pads
for IN, SYS, SW, BATT and PGND should be
connected to as many coppers planes on the
MP2635 Rev. 1.08
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30
MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
Design Example
Below is a design example following the
application guidelines for the specifications:
Table 3: Design Example
VIN
VOUT
fSW
5V
3.7V
1200kHz
Figure 14 shows the detailed application
schematic.
The
Typical
Performance
Characteristics section shows the typical
performance and circuit waveforms. For more
possible applications of this device, please refer
to the related Evaluation Board datasheets.
MP2635 Rev. 1.08
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MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
TYPICAL APPLICATION CIRCUITS
31.6k
63.4k
5.1k
5.1k
21.5k
15k
Figure 14: The detailed application circuit of MP2635
MP2635 Rev. 1.08
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MP2635 – 2A SINGLE CELL SWITCH MODE BATTERY CHARGER
PACKAGE INFORMATION
QFN24 (4x4mm)
3.90
4.10
2.50
2.80
19
PIN 1 ID
MARKING
18
3.90
4.10
PIN 1 ID
INDEX AREA
PIN 1 ID
SEE DETAIL A
24
1
0.50
BSC
2.50
2.80
0.18
0.30
6
13
0.35
0.45
TOP VIEW
12
7
BOTTOM VIEW
PIN 1 ID OPTION A
0.30x45º TYP.
PIN 1 ID OPTION B
R0.25 TYP.
0.80
1.00
0.20 REF
0.00
0.05
DETAIL A
SIDE VIEW
3.90
2.70
0.70
0.25
NOTE:
1) ALL DIMENSIONS ARE IN MILLIMETERS.
2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH.
3) LEAD COPLANARITY SHALL BE0.10 MILLIMETER MAX.
4) DRAWING CONFIRMS TO JEDEC MO-220, VARIATION VGGD.
5) DRAWING IS NOT TO SCALE.
0.50
RECOMMENDED LAND PATTERN
NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third
party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not
assume any legal responsibility for any said applications.
MP2635 Rev. 1.08
4/27/2016
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