Document Number: MC34673
Rev. 1.0, 01/2008
Freescale Semiconductor
Advance Information
* This document contains certain information on a new product.
Specifications and information herein are subject to change without notice.
© Freescale Semiconductor, Inc., 2007-8. All rights reserved.
High Input Voltage 1.2A Charger
for Single-cell Li-Ion Batteries
The MC34673 is a cost-effective fully-integrated battery charger for
Li-Ion or Li-Polymer batteries. The high input voltage, up to 28V,
eliminates the input over-voltage protection circuit required in handheld
devices such as PDAs, cell phones, portable video game players and
digital still cameras.
A typical charge cycle includes trickle, constant-current (CC) and
constant-voltage (CV) charge modes. The CC-mode current is
programmable up to 1.2A with an external resistor. The voltage across
the external resistor is also used to monitor the actual charge current.
The constant voltage is fixed at 4.2V with 0.7% accuracy over a -20°C
to 70°C temperature range. The trickle-mode current is preset to 20%
of the CC-mode current when the battery voltage is lower than the
trickle-mode threshold. The end-of-charge (EOC) current threshold is
preset to 10% of the CC-mode current to save the board space and
cost. A charge current thermal foldback feature limits the charge
current when the IC internal temperature rises to a preset threshold.
The MC34673 also protects the system with its input over-voltage
protection (OVP) feature. In addition, the MC34673 has a 2.6V falling
power-on-reset (POR) threshold, making it perfect to work with current
limited power supplies. Three indication pins (PPR, CHG and FAST)
can be simply interfaced to a microprocessor or LEDs. When no power
supply is connected, or when disabled, the charger draws less than
1.0µA leakage current from the battery.
Features
• No external MOSFET, reverse-blocking diode or current-sense resistor are required
• Guaranteed maximum 1.2A programmable CC-mode current
•±0.7% voltage accuracy over -20°C to 70°C
•±6% current accuracy over -40°C to 85°C
• 28V maximum voltage for the power input with 6.8V over-voltage protection threshold
• 2.6V minimum input operating voltage
• Trickle charge for fully discharged batteries
• Charge current monitor
• Charge current thermal foldback
• Pb-free packaging designated by suffix code EP
Figure 1. 34673 Simplified Application Diagram
POWER MANAGEMENT IC
EP SUFFIX (PB-FREE)
98ASA10774D
8-PIN UDFN
34673
ORDERING INFORMATION
Device Temperature
Range (TA)Package
MC34673AEP/R2 -40°C to 85°C 8-UDFN
VIN
ON
OFF
VIN
GND
CHG
PPR
EN
BAT
ISET
FAST
TO BATTERY
TO MCU
VIO
34673
CIN COUT
RISET
Analog Integrated Circuit Device Data
2Freescale Semiconductor
34673
INTERNAL BLOCK DIAGRAM
INTERNAL BLOCK DIAGRAM
Figure 2. 34673 Simplified Internal Block Diagram
+
–
Logic
+
–+
–
+–
+
–
+
–
Die
Temp
110°C
IEOC
VIN
BAT
VOS IREF
VREF
REF
Internal
VIN
Monitor
Charge
Control
BAT
ISET
FAST
VIN
PPR
CHG
EN
GND
Supply
Control
Analog Integrated Circuit Device Data
Freescale Semiconductor 3
34673
PIN CONNECTIONS
PIN CONNECTIONS
Figure 3. 34673 Pin Connections
Table 1. 34673 Pin Definitions
A functional description of each pin can be found in the Functional Pin Description section beginning on page 11.
Pin Number Pin Name Pin Function Formal Name Definition
1VIN Input Input supply The supply input.
2PPR Output Power present
indicator
Indication of the input power status. Open drain output.
3CHG Output Charge indicator Indication of the charge status. Open drain output.
4EN Input Enable Enable logic input.
5GND Ground Ground Ground.
6FAST Output Fast charge indicator Indication of the fast charge status. Open drain output.
7ISET Output CC-mode current
setting and charge
current monitor
CC-mode current setting and monitoring pin.
8BAT Output Charger output The charger output pin. Connect this pin to the Li-Ion battery.
EPAD EPAD N/A Exposed pad Exposed pad for thermal dissipation enhancement. Must be soldered on
the large ground plane on the PCB to increase the thermal dissipation.
The pad must be connected to GND electrically.
BAT
ISET
FAST
GND
VIN
PPR
CHG
EN
EPAD
1
2
3
4
8
7
6
5
Analog Integrated Circuit Device Data
4Freescale Semiconductor
34673
ELECTRICAL CHARACTERISTICS
MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
MAXIMUM RATINGS
Table 2. Maximum Ratings
All voltages are with respect to ground unless otherwise noted. Exceeding these ratings may cause a malfunction or
permanent damage to the device.
Ratings Symbol Value Unit
ELECTRICAL RATINGS
Input Voltage Range
VIN Pin
PPR and CHG Pins
EN, BAT, ISET, and FAST Pins
VIN
VPPR, VCHG
VEN, VBAT,
VISET, VFAST
-0.3 to 28
-0.3 to 12
-0.3 to 5.5
V
ESD Voltage(1)
Human Body Model (HBM)
Machine Model (MM)
VESD ±2000
±200
V
THERMAL RATINGS
Operating Temperature
Ambient
Junction
TA
TJ
-40 to 85
-40 to 150
°C
Storage Temperature TSTG -65 to +150 °C
Thermal Resistance(2)
Junction-to-Case
Junction-to-Ambient
RθJC
RθJA
10
70
°C/W
Peak Package Reflow Temperature During Reflow(3),(4) TPPRT Note 4 °C
Notes
1. ESD testing is performed in accordance with the Human Body Model (HBM) (CZAP = 100pF, RZAP = 1500Ω), and the Machine Model
(MM) (CZAP = 200pF, RZAP = 0Ω).
2. Device mounted on the Freescale EVB test board per JEDEC DESD51-2.
3. Pin soldering temperature limit is for 10 seconds maximum duration. Not designed for immersion soldering. Exceeding these limits may
cause malfunction or permanent damage to the device.
4. Freescale’s Package Reflow capability meets Pb-free requirements for JEDEC standard J-STD-020C. For Peak Package Reflow
Temperature and Moisture Sensitivity Levels (MSL), Go to www.freescale.com, search by part number [e.g. remove prefixes/suffixes
and enter the core ID to view all orderable parts. (i.e. MC33xxxD enter 33xxx), and review parametrics.
Analog Integrated Circuit Device Data
Freescale Semiconductor 5
34673
ELECTRICAL CHARACTERISTICS
STATIC ELECTRICAL CHARACTERISTICS
STATIC ELECTRICAL CHARACTERISTICS
Table 3. Static Electrical Characteristics
Characteristics noted under conditions VIN = 5.0V, -40°C ≤ TA ≤ 85°C, CIN =1µF, COUT = 2.2µF (see Figure 1), unless otherwise
noted. Typical values noted reflect the approximate parameter means at VIN = 5.0V and TA = 25°C under nominal conditions,
unless otherwise noted.
Characteristic Symbol Min Typ Max Unit
POWER INPUT
Input Voltage Range(5) VIN 2.6 -6.6 V
VIN Pin Supply Current
Charger enabled(6)
Charger disabled
IIN
-
-
1400
-
-
350
µA
Regulated Output Voltage
VIN = 5.0V; IBAT = 10mA; TA = 25°C
VIN = 5.0V; IBAT = 10mA; TA = -20 to 70°C
VIN = 5.0V; IBAT = 10mA; TA = -40 to 85°C
VBAT
4.185
4.170
4.158
4.20
4.20
4.20
4.215
4.230
4.230
V
Power MOSFET On Resistance
VBAT = 4.0V; IBAT = 500mA; ICHG = 600mA
RDS(ON)
-330 475
mΩ
BAT Pin Standby Current
VIN not powered or charger disabled
ISTDBY
- - 1.0
µA
Power On Reset
Rising VIN threshold
Falling VIN threshold
VPOR
3.0
-
-
2.4
3.9
2.6
V
VIN-BAT Offset Voltage
Rising threshold
Falling threshold
VOS
-
1.0
-
-
60
22
mV
Over-voltage Protection Rising Threshold VOVP 6.6 6.8 7.0 V
Over-voltage Protection-Threshold Hysteresis VOVPHYS -400 -mV
CHARGE CURRENT
Constant-current Mode Charge Current Range(7) ICHG 0.05 -1.2 A
ICHG Accuracy
For ICHG between 300mA to 1200mA (Tested at 450mA)
For ICHG between 50mA to 300mA(7)
ICHG
94
90
100
100
106
110
%
Trickle-Mode Charge Current ITRKL 16 20 24 % ICHG
End-of-Charge (EOC) Threshold
When ICHG is set to 450mA
IEOC
35 45 55
mA
ISET Pin Voltage for ICHG Reference(7) VISET -1.0 - V
Notes
5. Refer to the Power-on-Reset parameter for VIN turn on and turn off values.
6. Supply current does not include the current delivered to the battery through the BAT pin.
7. Not tested. Guaranteed by design.
Analog Integrated Circuit Device Data
6Freescale Semiconductor
34673
ELECTRICAL CHARACTERISTICS
STATIC ELECTRICAL CHARACTERISTICS
CHARGE THRESHOLDS
Trickle-Mode Rising Threshold Voltage VTRKL 2.6 2.7 2.8 V
Trickle-Mode Threshold Voltage Hysteresis VTRKLHYS 40 100 150 mV
Recharge Threshold Voltage VRECH 4.060 4.100 4.140 V
Recharge Falling Threshold Voltage Hysteresis VTHRCHG -25 50 mV
LOGIC INPUT AND OUTPUT
EN Input High Threshold Voltage VIH 1.5 - - V
EN Input Low Threshold Voltage VIL - - 0.5 V
EN Input Leakage Current
VEN = 3.0V
IEN
-2.0 7.5
µA
PPR and CHG Sink Current When the Output is Low
VCHG =VPPR = 0.6V
IPCSINKL
12 15 -
mA
PPR and CHG Leakage Current When the Output is High-impedance
VCHG =VPPR = 5.0V
IPCLEAKH
- - 1.0
µA
FAST Sink Current When the Output is Low
VFAST = 0.5.0V
IFSINKL
0.3 - -
mA
FAST Leakage Current When the Output is High-impedance
VFAST = 3.0V
IFLEAKH
- - 1.0
µA
CHARGE CURRENT THERMAL FOLDBACK
Current Foldback Die Temperature Limit TLIMIT 95 110 125 °C
Table 3. Static Electrical Characteristics (continued)
Characteristics noted under conditions VIN = 5.0V, -40°C ≤ TA ≤ 85°C, CIN =1µF, COUT = 2.2µF (see Figure 1), unless otherwise
noted. Typical values noted reflect the approximate parameter means at VIN = 5.0V and TA = 25°C under nominal conditions,
unless otherwise noted.
Characteristic Symbol Min Typ Max Unit
Analog Integrated Circuit Device Data
Freescale Semiconductor 7
34673
ELECTRICAL CHARACTERISTICS
DYNAMIC ELECTRICAL CHARACTERISTICS
DYNAMIC ELECTRICAL CHARACTERISTICS
Table 4. Dynamic Electrical Characteristics
Characteristics noted under conditions VIN = 5.0V, -40°C ≤ TA ≤ 85°C, CIN =1µF, C OUT = 2.2µF (Figure 1), unless otherwise
noted. Typical values noted reflect the approximate parameter means at VIN = 5.0V and TA = 25°C under nominal conditions,
unless otherwise noted.
Characteristic Symbol Min Typ Max Unit
END OF CHARGE
EOC Filter Time tEOC 5.5 8.0 11 ms
OSCILLATOR
Oscillation Frequency fOSC 40.0 50.0 60.0 kHz
Analog Integrated Circuit Device Data
8Freescale Semiconductor
34673
ELECTRICAL CHARACTERISTICS
ELECTRICAL PERFORMANCE CURVES
ELECTRICAL PERFORMANCE CURVES
Figure 4. Complete Charge Cycle
VIN = 5.0V, ICHG=300mA, TA = 25°C
Figure 5. VBAT vs VIN
IBAT = 0mA, TA = 25°C
Figure 6. VIN Pin Supply Current vs VIN
IBAT=0mA, TA = 25°C
Figure 7. Constant Charge Current vs VIN
VBAT = 3.0V, TA = 25°C
Figure 8. Trickle Charge Current vs VIN
VBAT = 2.0V, TA = 25°C
Figure 9. VISET vs VIN
VBAT = 3.9V, TA = 25°C
0 20406080100120
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0
50
100
150
200
250
300
350
Charge Current (mA)
Charge Current
Battery Voltage (V)
Charge Time (min)
Battery Voltage
4.04.55.05.56.06.5
3.6
3.8
4.0
4.2
4.4
VBAT (V)
VIN (V)
2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
500
1000
1500
2000
2500
3000
Charger Enabled
VIN Pin Supply Current (µA)
VIN (V)
Charger Disabled
3.54.04.55.05.56.06.5
300
600
900
1200
1500
RISET=3.23 kΩ
RISET=6.57 kΩ
Constant Charge Current (mA)
VIN (V)
RISET=13.3 kΩ
3.54.04.55.05.56.06.5
0
50
100
150
200
250
RISET=13.3 kΩ
RISET=3.23 kΩ
RISET=6.57 kΩ
Trickle Charge Current (mA)
VIN (V)
4.4 4.8 5.2 5.6 6.0 6.4 6.8
0.0
0.2
0.4
0.6
0.8
1.0
1.2
VISET (V)
VIN (V)
Analog Integrated Circuit Device Data
Freescale Semiconductor 9
34673
ELECTRICAL CHARACTERISTICS
ELECTRICAL PERFORMANCE CURVES
Figure 10. VISET vs Charge Current
VIN = 5.0V, TA = 25°C
Figure 11. Charge Current vs VBAT
VIN = 5.0V, TA = 25°C
Figure 12. VBAT vs Temperature
VIN = 5.0V, IBAT = 0mA
Figure 13. Constant Charge Current vs Temperature
VIN = 5.0V, VBAT = 3.9V
Figure 14. Trickle Charge Current vs Temperature
VIN = 5.0V, VBAT = 2.0V
Figure 15. VISET vs Temperature
VIN = 5.0V
0 200 400 600 800 1000 1200
0.0
0.2
0.4
0.6
0.8
1.0
1.2
RISET=3.23 kΩ
RISET=13.3 kΩRISET=6.57 kΩ
VISET (V)
Charge Current (mA)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
0
300
600
900
1200
1500
RISET=13.3 kΩ
RISET=3.23 kΩ
RISET=6.57 kΩ
Charge Current (mA)
VBAT (V)
-40-200 20406080
4.00
4.05
4.10
4.15
4.20
4.25
4.30
VBAT (V)
Temperature (oC)
-40 -20 0 20 40 60 80
0
200
400
600
800
1000
1200
RISET=3.95 kΩ
RISET=19.36 kΩ
Constant Charge Current (mA)
Temperature (oC)
RISET=6.11 kΩ
-40-20 0 20406080
0
50
100
150
200
250
RISET=19.36 kΩ
RISET=3.95 kΩ
RISET=6.11 kΩ
Trickle Charge Current (mA)
Temperature (oC)
-40 -20 0 20 40 60 80
0.0
0.2
0.4
0.6
0.8
1.0
1.2
VISET (V)
Temperature (oC)
Analog Integrated Circuit Device Data
10 Freescale Semiconductor
34673
ELECTRICAL CHARACTERISTICS
ELECTRICAL PERFORMANCE CURVES
Figure 16. RDS(ON) vs Temperature
VBAT = 4.0V, ICHG=300mA, IBAT= 250mA
Figure 17. Recharge Voltage Threshold vs Temperature
RISET = 25.86kΩ, VIN = 5.0V
Figure 18. BAT Pin Supply Current vs Temperature
VBAT = 5.0V, VIN Not Powered or Charger Disabled
Figure 19. VIN Pin Supply Current vs Temperature
VIN = 5.0V
-40-200 20406080
250
300
350
400
450
RDS(ON) (mΩ)
Temperature (oC)
-40-20 0 20406080
3.90
3.95
4.00
4.05
4.10
4.15
4.20
Recharge Voltage Threshold (V)
Temperature (oC)
-40-20 0 20406080
0.0
0.2
0.4
0.6
0.8
1.0
BAT Pin Supply Current (µA)
Temperature (oC)
-40 -20 0 20 40 60 80
0
250
500
750
1000
1250
1500
1750
2000
Charger Enabled
VIN Pin Supply Current (µA)
Temperature (oC)
Charger Disabled
Analog Integrated Circuit Device Data
Freescale Semiconductor 11
34673
FUNCTIONAL DESCRIPTION
INTRODUCTION
FUNCTIONAL DESCRIPTION
INTRODUCTION
The MC34673 is a fully-integrated Li-Ion and Li-Polymer
battery charger in a tiny package. It uses current, voltage and
temperature control loops to regulate the charge current. It
has up to 28V input voltage rating, which makes the handheld
device safe even when connected to a wrong AC adapter.
The MC34673 requires only two external capacitors and
one resistor to build a fully functional charger for space-
limited applications such as PDAs, cell phones, portable
video game players and digital still cameras. Its ultra high-
accuracy (±0.7%) output voltage and temperature-limited
charging current offer additional battery safety during
charging.
The CC-mode current can be programmed with an
external resistor (RISET). The voltage across this resistor is
proportional to the charge current, so the system can monitor
the charge current during the whole charge cycle. The EOC
current threshold is preset to 10% of the CC-mode current.
For a deeply discharged battery with a voltage lower than
2.7V, the MC34673 charges the battery with a trickle-mode
current, which is 20% of the CC-mode current.
Three indication outputs make it easy to report the input
power status and the charge status to MCUs, or users via
LEDs.
FUNCTIONAL PIN DESCRIPTION
INPUT SUPPLY (VIN)
The supply input. This pin should be bypassed to ground
with a 1.0µF capacitor.
POWER PRESENT INDICATOR (PPR)
Open-drain logic output to indicate the input power status.
The PPR-pin output is only determined by the input voltage,
not other conditions such as the EN pin input. The output is
low if VIN is higher than VPOR. This pin is capable to sink at
least 12.0mA current to drive a LED indicator.
CHARGE INDICATOR (CHG)
Open-drain logic output to indicate the charge status. The
output is low when the MC34673 is charging, until the EOC
conditions are reached. This pin is capable to sink at least
12.0mA current to drive a LED indicator.
ENABLE (EN)
Active-low enable logic Input. This pin is internally pulled
to ground by a weak current source. When left floating, the
charger is enabled. Pulling this pin to high voltage externally
disables the charger.
GROUND (GND)
Ground.
FAST CHARGE INDICATOR (FAST)
When charging, this open-drain logic output indicates
whether or not the battery voltage is higher than the trickle-
mode threshold. This pin is capable to sink more than 0.3mA
current. When the charger is on, this pin outputs a logic low
signal if the battery voltage is higher than the trickle-mode
threshold. When the charger is in the shutdown mode or in
any fault conditions, this pin outputs high-impedance.
CC-MODE CURRENT SETTING AND CHARGE
CURRENT MONITOR (ISET)
The CC-mode current, ICHG, is programmed by connecting
a resistor, RISET, between this pin and the ground. When
charging in the CC-mode, the voltage at this pin is 1.0V. The
voltage reduces proportionally as the charge current reduces
in the CV-mode. During the whole charge cycle, the voltage
at this pin can be used to monitor the charge current using the
following equation:
equ. 1
where IBAT is the actual charge current, ICHG is the
programmed CC-mode current, and VISET is the voltage of
the ISET pin during the whole charge cycle.
CHARGER OUTPUT (BAT)
Charger output pin. Connect this pin to the battery being
charged. Bypass to ground with a 2.2µF or higher capacitor.
EXPOSED PAD (EPAD)
Exposed pad. Must be soldered on the large ground plane
on the PCB to enhance the thermal conductivity. The pad
must be connected to GND electrically.
IBAT VISET
1.0V
--------------- ICHG
⋅=
Analog Integrated Circuit Device Data
12 Freescale Semiconductor
34673
FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
Figure 20. 34673 Functional Internal Block Diagram
INTEGRATED SUPPLY
INTERNAL SUPPLY AND REFERENCE
This block steps down the high input voltage to a lower
voltage to power all the internal blocks. In addition, this block
generates the reference voltage for the charge-control block.
SENSING AND CONTROL
VIN MONITOR
The input voltage monitor block monitors the input voltage
for two thresholds, power-on-reset (POR) and over-voltage
protection (OVP). If the input is lower than the POR or higher
than the OVP threshold, this block outputs a logic signal to
disable the charger.
CHARGE CONTROL
The charge-control block controls the gate voltage of the
power MOSFET to regulate the charge current, the battery
voltage, or the die temperature. It can also completely turn off
the power MOSFET to stop the current flow between the
input and the battery. Also, monitoring of the charge current
and the charger output voltage determines the trickle-charge
mode and the recharge cycle.
CURRENT SETTING AND MONITOR
This block programs the charge current in the constant-
current mode and monitors the actual charge current during
the whole charge cycle.
EOC (END OF CHARGE)
The EOC block monitors the charge current and the
battery voltage for the EOC conditions. Once the EOC
conditions are reached, this block outputs a logic signal to
indicate the end of the charge.
VIN-BAT COMPARATOR
The VIN-BAT comparator monitors the voltage difference
between the input voltage and the battery voltage. The input
voltage has to be higher than the battery voltage for the
charger to be enabled. If the input voltage falls below the
battery voltage, this block outputs a signal to disable the
charger to prevent the leakage current from the battery to the
input.
DIE TEMPERATURE FEEDBACK
The die temperature feedback block monitors the die
temperature. Once the die temperature reaches the
threshold temperature, the charge-control block can reduce
the charge current to prevent further die temperature rise.
MC34673 - Functional Block Diagram
Integrated Supply
Sensin
g
& Contro
l
M
OS
FET
P
ower M
OS
FET
Log
ic
Integrated Supply
Internal Supply & Reference
Sensin
g
& Control
L
o
g
i
c
e
emperature
ee
ac
Current Setting
Cu
rr
e
nt M
o
nit
o
r
S
t
a
t
us
In
d
i
ca
ti
on
V
IN - BAT
C
ompare
V
IN
M
on
i
to
r
C
harge Contro
l
Logic Contro
l
E
nd of Charge
Analog Integrated Circuit Device Data
Freescale Semiconductor 13
34673
FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
LOGIC
LOGIC CONTROL AND STATUS INDICATION
The logic control block determines the on and off of the
charger. It takes the signals from the VIN Monitor, VIN-BAT
Comparator, EOC, and the external enable signal, and
determines the on and off states as well as the charge status
indication outputs of the charger (CHG, PPR, and FAST).
POWER MOSFET
The power MOSFET passes the charging current from the
input to the output.
Analog Integrated Circuit Device Data
14 Freescale Semiconductor
34673
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
CHARGE CYCLE
The MC34673 uses the standard charge profile with
trickle, constant-current (CC), and constant-voltage (CV)
charge modes, as shown in Figure 21. Both the CC and the
CV charge modes are also called fast-charge mode. When
the input voltage rises above an internal power-on-reset
threshold, the PPR pin outputs a low voltage to indicate the
power-supply presence. The charger starts with the trickle-
charge mode until the battery voltage is above 2.7V. The
CHG pin outputs logic low voltage at the beginning of the
trickle-charge mode. If the battery voltage is unable to rise
due to a battery failure, charging will remain in the trickle-
charge mode. When the battery voltage reaches the 2.7V
threshold, the MC34673 softly changes to the CC-mode. The
soft transition minimizes the input-voltage drop and reduces
the requirement of the input decoupling capacitance. In the
fast-charge mode, the FAST pin outputs a low voltage. When
the battery voltage reaches 4.2V, the MC34673 enters the
CV-mode and regulates the output voltage at 4.2V. The
charge current decreases gradually in the CV-mode. When
the current drops to the EOC current threshold, the MC34673
outputs logic high voltage at the CHG pin to indicate that the
charging is completed.
After the charging is completed, the MC34673 continues to
regulate the output to 4.2V, and monitors the output voltage.
If a load is in parallel with the battery, the charger continues
to output the current to the load even the charge is
completed. If the load current exceeds the programmed CC-
mode current, the battery will supply the additional current to
the load and the battery voltage will decline. Once the battery
voltage drops below the recharge voltage threshold, the
MC34673 returns to the fast-charge mode and indicates a
low voltage at the CHG pin.
When one of the following three conditions happens, the
MC34673 is disabled.
1. VIN > VOVP
2. VIN - VBAT < VOS
3. EN pin is high
where VOS is the offset voltage for the comparator that
monitors the input and the battery voltages.
Figure 22 shows the complete charge-cycle state
diagram.
Figure 21. Charge Profile
CHARGE CURRENT SETTING
An external resistor between the ISET pin and the ground
programmes the CC-mode current with the following
equation:
equ. 2
where RISET is the resistor between the ISET pin and the
ground in Ω. In addition, the current out of the ISET pin is
proportional to the charge current. The system may measure
ICHG
Trickle Constant Voltage
ITRKL
IEOC
4.2V
TIME
2.7V
CHG
Charge
Current
Charge
Voltage
TIME
FAST
TIME
ILOAD
>ICHG
100mV
Constant Current
ICHG 4000
RISET 96+
---------------------------
=
Analog Integrated Circuit Device Data
Freescale Semiconductor 15
34673
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
the ISET pin voltage to monitor the actual charge current as
given in equ. 1 during the whole charging cycle.
CHARGE CURRENT LIMITATION
The charge current is limited by multiple factors.
When the voltage difference between the input and the
battery (VIN - VBAT) is low, (VIN - VBAT) / RDS(ON), where
RDS(ON) is the on resistance of the power MOSFET, may be
less than the programmed CC-mode current ICHG. The
charge current is limited by (VIN - VBAT) / RDS(ON) in this case.
When the voltage difference between the input and the
battery is too high, the large power dissipation may lead to
the charge-current thermal-foldback operation due to the die
temperature regulation. The charge current is reduced to
prevent further temperature rise (See Charge Current
Thermal Foldback).
DC INPUT VOLTAGE
The MC34673 accepts up to 28V DC input. When all of the
following conditions are satisfied, the input is in a power-good
range for the charger to start charging. The conditions
include:
1. VIN > VPOR
2. VIN - VBAT > VOS
3. VIN < VOVP
where VOS is the offset voltage for the comparator that
monitors the input and the battery voltages. The VOS is for
preventing the reverse leakage current from the battery when
the power supply is off. VOVP is the over-voltage protection
threshold. When the DC input voltage is above the over-
voltage protection threshold, the charger is disabled
internally. The 28V input voltage rating eliminates the need of
any additional input over-voltage protection circuitry.
CHARGE-ENABLE INPUT
The charge-enable input, EN, has a weak internal pull-
down current. Driving it to a low logic voltage, leaving it
floating, or shorting it to the ground will enable the charger, if
the input voltage is in the power-good range. Whenever the
EN pin is driven to a high logic voltage, the charger is
disabled.
INPUT POWER PRESENCE INDICATOR
When VIN is applied and the voltage is above the power-on-
reset voltage threshold (VPOR), the PPR pin outputs a low
voltage to indicate the input power presence. The PPR out-
put is only controlled by the input voltage. All other functions,
such as the EN pin, the over-voltage protection, and the VIN-
BAT comparator, do not affect the PPR output. The PPR pin
is capable to sink at least 12.0mA current when outputting a
low voltage to drive an external LED.
CHARGE STATUS INDICATORS
The MC34673 has two charge status indicators, CHG and
FAST. CHG outputs a low voltage when the charger is
enabled and the charging is in progress. When the charge
cycle completes, CHG outputs high-impedance. If the
charger is disabled or the input voltage is out of the power-
good range, the CHG pin outputs high-impedance as well.
The CHG pin has at least 12.0mA current-sinking capability
to drive an external LED, same as the PPR pin.
FAST indicates whether the MC34673 is in the fast-charge
mode or not. When the charger is on and the battery voltage
is higher than the trickle-mode threshold, the charger enters
the fast-charge mode and FAST outputs a low voltage. The
open-drain FAST pin requires a pull-up resistor to output the
logic signal. If the charger is in the trickle-charge mode or is
disabled, or when the input voltage is out of the power-good
range, the FAST pin outputs high-impedance.
CHARGE CURRENT THERMAL FOLDBACK
An internal thermal feedback loop begins to reduce the
charge current when the die temperature reaches 110°C to
prevent further temperature rise. This feature protects the
MC34673 from over-temperature failures and allows the user
to push the limits of the power handling capability of a given
circuit board without the risk of damaging the MC34673. The
charge current can be programmed according to the typical
(not the worst-case) ambient temperature with the assurance
that the charger will automatically reduce the current in worst-
case conditions.
Analog Integrated Circuit Device Data
16 Freescale Semiconductor
34673
FUNCTIONAL DEVICE OPERATION
STATE DIAGRAM
STATE DIAGRAM
Figure 22. Charge Cycle State Diagram
TRICKLE
CHARGE
Charger: ON
FAST CHARGE
Charger: ON
CHARGE
COMPLETE
Charger: ON
VIN>VPOR
EN=low
and VIN<VOVP
and VIN>VBAT+VOS
VBAT > 2.7V
VBAT=4.2V
and IBAT < IEOC
VBAT<4.10V
EN=high
or VIN>VOVP
or VIN<VBAT+VOS SHUTDOWN
Charger: OFF
PWR OFF
Charger: OFF
VIN<VPOR
VBAT < 2.7V
VBAT < 2.7V
Analog Integrated Circuit Device Data
Freescale Semiconductor 17
34673
TYPICAL APPLICATIONS
INTRODUCTION
TYPICAL APPLICATIONS
INTRODUCTION
INPUT CAPACITOR
The input capacitor is used to reduce the input voltage
transient that may cause instability. A 1.0µF, X5R, 16V rated
ceramic capacitor is recommended for most applications.
OUTPUT CAPACITOR
For stable operation, an X5R ceramic capacitor with a
minimum 2.2µF nominal value is recommended at the output.
Depending on the load transient current, larger capacitance
may be required.
CC-MODE CURRENT SETTING
The CC-mode current can be programmed by the external
resistor, RISET. A 1% accuracy resistor is recommended to
guarantee 6% current accuracy.
DROPOUT VOLTAGE
If the DC input voltage is too low, it may not maintain the
programmed CC-mode charge current due to the voltage
dropout over the power MOSFET. The worst case of the
RDS(ON) is 475mΩ. The input voltage should be at least
higher than VBAT + ICHG x 475mΩ to guarantee the
programmed CC-mode current.
THERMAL CONSIDERATIONS
The MC34673 is available in a tiny 2x3 thermally-
enhanced UDFN package. A careful thermal design must be
considered. The exposed pad needs to be well soldered to a
large copper ground plane on the component layer. If the
component layer is space limited and does not allow for a
large copper plane, the thermal pad must be connected to
other ground layers through a via array. This allows
MC34673 to charge the battery with the maximum current,
while minimizing the die temperature.
APPLICATIONS
STAND-ALONE CHARGER
The MC34673 can be used in a standalone charger
without MCUs. Figure 23 shows such an application. The
green LED indicates the power presence and the red LED
indicates the charge status. In total, only 7 external
components are required.
Figure 23. Stand Alone Li+ Battery Charger
VIN
GND
ISET
BAT
CHG
PPR FAST
EN
Input
REDGREEN
1µF 2.2µF
Li+
5.23k
470470
MC34673
Analog Integrated Circuit Device Data
18 Freescale Semiconductor
34673
TYPICAL APPLICATIONS
APPLICATIONS
MCU INTERFACED CHARGER
When the charger is used in handheld systems with MCU
control, the MC34673 uses PPR to report the DC input status
to the MCU. After the MCU pulls the EN pin to a logic-low
voltage to start charging, the MC34673 reports the charge
status through CHG and FAST pins to the MCU. The MCU
can also monitor the charge current by measuring the voltage
at the ISET pin. Figure 24 is the typical application circuit.
Figure 24. MCU Interfaced Charger
VIN
GND
ISET
BAT
VIO
CHG
PPR
FAST
EN OFF
ON
Input
MCU
Li+
1µF 2.2µF
5.23k
100kx3
Analog Integrated Circuit Device Data
Freescale Semiconductor 19
34673
TYPICAL APPLICATIONS
PACKAGE DIMENSIONS
PACKAGE DIMENSIONS
For the most current package revision, visit www.freescale.com and perform a keyword search using the “98A” listed below.
EP SUFFIX
8-PIN
98ASA10774D
REVISION 0
Analog Integrated Circuit Device Data
20 Freescale Semiconductor
34673
TYPICAL APPLICATIONS
PACKAGE DIMENSIONS
EP SUFFIX
8-PIN
98ASA10774D
REVISION 0
Analog Integrated Circuit Device Data
Freescale Semiconductor 21
34673
REVISION HISTORY
REVISION HISTORY
REVISION DATE DESCRIPTION OF CHANGES
1.0 1/2008 • Initial Release
MC34673
Rev. 1.0
01/2008
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