MAX8969
Step-Up Converter for Handheld Applications
General Description
Benefits and Features
The IC transitions to skip mode seamlessly under lightload conditions to improve efficiency. Under these conditions, switching occurs only as needed, reducing switching
frequency and supply current to maintain high efficiency.
●● Integrated Protection Increases System Robustness
• Undervoltage Lockout (UVLO)
• Short-Circuit Protection
• Overtemperature Shutdown
For higher efficiency when input voltage is closer to the
output voltage, two special modes of operation are available: track and automatic track. These modes allow users
to balance quiescent current (IQ) vs. transient response
time into boost mode. In both modes, the p-channel
MOSFET acts as a current-limited switch such that VOUT
follows VIN. However, in track mode, the boost circuits
are disabled and the system controls the boost function with the EN, TREN inputs (IQ = 30µA). In automatic
track mode (ATM), the boost circuits are enabled and the
device automatically transitions into boost mode when
VIN falls to 95% of the target VOUT (IQ = 60µA).
●● High Efficiency and Low Quiescent Current Extends
Battery Life
• Over 90% Efficiency with Internal Synchronous
Rectifier
• 60µA IQ in Automatic Track Mode
• 45µA IQ in Step-Up Mode
• 30µA IQ in Track Mode
• 1µA Shutdown Current
• Skip Mode Under Light Load Condition Improves
Efficiency
• True Shutdown™ Prevents Current Flow from
OUT_ to LX_
• Soft-Start Limits Inrush Current to 480mA
The MAX8969 is a simple 1A step-up converter in a small
package that operates in any single-cell Li-ion application.
This IC provides protection features such as input undervoltage lockout, short circuit, and overtemperature shutdown.
The IC is available in a small, 1.25mm x 1.25mm, 9-bump
WLP (0.4mm pitch) package.
Applications
●●
●●
●●
●●
●●
Cell Phones
Smartphones
Mobile Internet Devices
GPS, PND
eBooks
●● Flexible System Integration
• Up to 1A Output Current
• 2.5V to 5.5V Input Voltage Range
• 3.3V to 5.5V Output Voltage Options
●● Small Package and High Frequency Operation
Reduce Board Space
• 9-Bump 1.25mm x 1.25mm WLP Package
• 3MHz PWM Switching Frequency
• Small External Components
Typical Operating Circuit
L1
1µH
INPUT
2.5V TO 5.5V
CIN
4.7µF
IN
LX_
EN
True Shutdown is a trademark of Maxim Integrated Products, Inc.
19-6038; Rev 7; 4/20
OUTPUT
3.7V, 1A
COUT
22µF
MAX8969
Ordering Information appears at end of data sheet.
OUT_
TREN
GND_
MAX8969
Step-Up Converter for Handheld Applications
Absolute Maximum Ratings
IN, OUT_ to GND_................................................-0.3V to +6.0V
EN, TREN to GND_............ -0.3V to lower of (VIN + 0.3V) or 6V
Total LX_ RMS Current (Note 1)....................................3.2ARMS
OUT_ Short Circuit to GND_......................................Continuous
Continuous Power Dissipation (TA = +70°C)
WLP (derate 12mW/NC above +70°C)........................960mW
Operating Temperature Range.............................-40ºC to +85°C
Junction Temperature.......................................................+150°C
Storage Temperature Range............................. -65°C to +150°C
Soldering Temperature (reflow) (Note 2).......................... +260°C
Note 1: LX_ has internal silicon diodes to GND_ and OUT_. It is normal for these diodes to briefly conduct during LX_ transitions.
Avoid steady state conduction of these diodes.
Note 2: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile that the
device can be exposed to during board level solder attach and rework. This limit permits only the use of the solder profiles recommended in the industry-standard specification JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and Convection
reflow. Preheating is required. Hand or wave soldering is not allowed.
Stresses beyond those listed under “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 for extended periods may affect device reliability.
Package Thermal Characteristics (Note 1)
WLP
Junction-to-Ambient Thermal Resistance (θJA)...........83°C/W
Junction-to-Case Thermal Resistance (θJC)................50°C/W
Note 3: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Electrical Characteristics
(VIN = 2.6V, TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = +25°C.) (Note 4)
PARAMETER
CONDITIONS
MIN
Operating Input Voltage Range
2.5
Minimum Startup Voltage
VIN falling, 75mV hysteresis
Shutdown Supply Current
VEN = VTREN = VOUT = 0V,
VIN = 4.8V
Thermal Shutdown Temperature
TJ rising, 20°C hysteresis
Peak Output Current
Minimum Continuous Output Current
Switching Frequency
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MAX
UNITS
5.5
V
2.3
Undervoltage Lockout Threshold (UVLO)
BOOST MODE
TYP
2.1
TA = +25°C
TA = +85°C
VIN > 2.5V, pulse loading (Note 5)
VIN > 2.5V (Note 5)
(Note 6)
V
2.2
2.3
0.8
5
1
V
µA
+165
°C
1
A
VOUT = 3.3V
0.9
VOUT = 3.7V
0.7
VOUT = 5.0V
0.7
VOUT = 3.5V
0.8
VOUT = 4.25V
0.7
VOUT = 5.3V
0.7
VOUT = 5.5V
0.7
3
A
MHz
Maxim Integrated │ 2
MAX8969
Step-Up Converter for Handheld Applications
Electrical Characteristics (continued)
(VIN = 2.6V, TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = +25°C.) (Note 4)
PARAMETER
Output Voltage Accuracy
Steady-State Output Voltage
CONDITIONS
MIN
TYP
MAX
No load, VOUT_TARGET = 3.3V
3.175
3.30
3.40
No load, VOUT_TARGET = 3.5V
3.40
3.50
3.60
No load, VOUT_TARGET = 3.7V
3.64
3.75
3.85
No load, VOUT_TARGET = 4.25V
4.10
4.25
4.35
No load, VOUT_TARGET = 5V
4.85
5.00
5.10
No load, VOUT_TARGET = 5.3V
5.14
5.3
5.46
No load, VOUT_TARGET = 5.5V
5.39
5.5
5.65
2.5V < VIN < VATMRT, conditions emulating
0 < IOUT < 1A, COUT = 22µF, L = 1µH,
VOUT_TARGET = 3.3V
3.00
3.45
2.5V < VIN < VATMRT, conditions emulating
0 < IOUT < 1A, COUT = 22µF, L = 1µH,
VOUT_TARGET = 3.5V
3.15
3.65
2.5V < VIN < VATMRT, conditions emulating
0 < IOUT < 1A, COUT = 22µF, L = 1µH,
VOUT_TARGET = 3.7V
3.35
3.85
2.5V < VIN < VATMRT, conditions emulating
0 < IOUT < 600mA, COUT = 22µF, L = 1µH,
VOUT_TARGET = 4.25V
3.95
4.35
2.5V < VIN < VATMRT, conditions emulating
0 < IOUT < 500mA, COUT = 22µF, L = 1µH,
VOUT_TARGET = 5V
4.50
5.10
2.5V < VIN < VATMRT, conditions emulating
0 < IOUT < 500mA, COUT = 22µF, L = 1µH,
VOUT_TARGET = 5.3V
4.95
5.51
2.5V < VIN < VATMRT, conditions emulating
0 < IOUT < 400mA, COUT = 22µF, L = 1µH,
VOUT_TARGET = 5.5V
5.00
5.65
TA = +25°C
LX_ Leakage Current
VLX = 0V, 4.8V
Skip-Mode Supply Current
EN = high, IOUT = 0A, 1µH inductor (TREN is
low, not switching)
0.1
TA = +85°C
45
pMOS Turn-Off Current (Zero-Cross Current)
LX_ nMOS Current Limit
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2.6
83
0
V
V
µA
µA
10
2.1
Maximum Duty Cycle
Minimum Duty Cycle
5
0.2
UNITS
mA
3.2
A
%
%
Maxim Integrated │ 3
MAX8969
Step-Up Converter for Handheld Applications
Electrical Characteristics (continued)
(VIN = 2.6V, TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = +25°C.) (Note 4)
PARAMETER
pMOS On-Resistance
nMOS On-Resistance
CONDITIONS
MIN
120
VOUT = 3.5V
115
VOUT = 3.7V
110
VOUT = 4.25V
100
VOUT = 5V
91
VOUT = 5.3V
80
VOUT = 5.5V
79
VOUT = 3.3V
65
VOUT = 3.5V
63
VOUT = 3.7V
60
VOUT = 4.25V
55
VOUT = 5V
51
VOUT = 5.3V
43
VOUT = 5.5V
Minimum P1 Soft-Start Current Limit
VOUT = 5V
Output Voltage Ripple
TRACK MODE
pMOSFET On-Resistance
TYP
VOUT = 3.3V
MAX
UNITS
mΩ
mΩ
43
0.48
A
IOUT = 150mA, circuit of Figure 1
20
mVP-P
IOUT = 500mA, VIN = 2.7V
130
IOUT = 500mA, VIN = 3.2V
110
Track Current Limit
VOUT = 3.6V
Track Mode Quiescent Current
EN = low, TREN = high
1
mΩ
2
A
30
µA
65
µA
AUTOMATIC TRACK MODE (ATM)
ATM Supply Current
ATM VIN Rising Threshold (VATMRT)
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VIN = 5.4V
VOUT_TARGET = 3.3V
3.15
VOUT_TARGET = 3.5V
3.35
VOUT_TARGET = 3.7V
3.55
VOUT_TARGET = 4.25V
4.04
VOUT_TARGET = 5V
4.74
VOUT_TARGET = 5.3V
5.03
VOUT_TARGET = 5.5V
5.28
V
Maxim Integrated │ 4
MAX8969
Step-Up Converter for Handheld Applications
Electrical Characteristics (continued)
(VIN = 2.6V, TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = +25°C.) (Note 4)
PARAMETER
ATM VIN Falling Threshold (VATMFT)
Boost to ATM Transition Time
(tATM_ENTER)
CONDITIONS
MIN
TYP
VOUT_TARGET = 3.3V
3.10
VOUT_TARGET = 3.5V
3.29
VOUT_TARGET = 3.7V
3.5
VOUT_TARGET = 4.25V
3.99
VOUT_TARGET = 5V
4.69
VOUT_TARGET = 5.3V
4.98
VOUT_TARGET = 5.5V
5.23
(Note 6)
ATM to Boost Transition Time
(tATM_EXIT)
MAX
UNITS
V
1
µs
1
µs
LOGIC CONTROL
EN, TREN Logic Input High Voltage
EN, TREN Logic Input Low Voltage
EN, TREN Leakage Current
2.3V < VIN < 5.5V
2.3V < VIN < 5.5V
VEN = VTREN = 0V
1.05
V
0.4
TA = +25°C
TA = +85°C
-1
0.01
0.1
+1
V
µA
Note 4: Specifications are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by
design and characterization.
Note 5: The device supports a peak output current of 1A. Continuous operation with 1A output current at elevated temperature is not
guaranteed. With sustained high current (> 100ms, > 1A), the junction temperature (TJ) rises to the thermal shutdown threshold. The stated Minimum Continuous Output Current values represent what the typical operating circuit can achieve when
considering device and component variations. See the Output Current section for more information.
Note 6: Switching frequency decreases if input voltage is > 83% of the output voltage selected. This allows duty factor to drop to
values necessary to boost output voltage less than 25% without the use of pulse widths less than 60ns.
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Maxim Integrated │ 5
MAX8969
Step-Up Converter for Handheld Applications
Typical Operating Characteristics
(VIN = 3.6V, COUT = 22µF, X5R, 6.3V local and 10µF, X5R, 6.3V, 1µH inductor, circuit of Figure 1, TA = +25°C, unless otherwise noted.)
90
VIN = 2.5V
88
85
VIN = 3.1V
VIN = 2.5V
80
VIN = 3.6V
75
70
65
82
L = TOKO DFE252012 1µH
80
1
10
1
100
OUTPUT VOLTAGE (VOUT = 3.7V)
vs. OUTPUT CURRENT
OUTPUT VOLTAGE (VOUT = 5V)
vs. OUTPUT CURRENT
5.05
MAX8969 toc04
3.6
VIN = 3.6V
4.95
VIN = 4.3V
4.90
4.85
4.80
VIN = 3.2V
4.75
4.70
400
600
800
0
200
OUTPUT CURRENT (mA)
IOUT = 1000mA
3.5
IOUT = 600mA
3.0
5.5
AUTOMATIC
FREQUENCY
ADJUSTMENT
4.5
4.0
1000
IOUT = 10mA I
OUT = 100mA IOUT = 600mA
AUTOMATIC
IOUT = 1000mA FREQUENCY
AUTOMATIC
ADJUSTMENT TRACK MODE
TRANSITION
3.5
2.5
3.0
3.5
INPUT VOLTAGE (V)
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4.0
4.5
2.5
3.0
3.5
4.0
4.5
INPUT VOLTAGE (V)
1000
OUTPUT VOLTAGE (VOUT = 5.5V)
vs. OUTPUT CURRENT
toc06
5.4
VIN = 4.5V
VIN = 4.2V
VIN = 3.7V
VIN = 3.3V
VIN = 3.0V
VIN = 2.7V
5.3
5.2
0.0
0.2
0.4
0.6
0.8
5.0
5.5
OUTPUT VOLTAGE (VOUT = 5.5V)
vs. INPUT VOLTAGE
6.0
1.0
toc09
5.5
5.0
IOUT = 1mA
IOUT = 100mA
IOUT = 500mA
IOUT = 800mA
4.5
AUTOMATIC
TRACK MODE
TRANSITION
4.0
3.5
3.0
2.5
100
OUTPUT CURRENT (A)
5.0
OUTPUT VOLTAGE (V)
IOUT = 10mA
4.0
800
OUTPUT VOLTAGE (VOUT = 5V)
vs. INPUT VOLTAGE
MAX8969 toc07
AUTOMATIC
TRACK MODE
TRANSITION
IOUT = 100mA
4.5
600
10
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (VOUT = 3.7V)
vs. INPUT VOLTAGE
5.0
400
1
5.5
5.0
4.55
1000
VIN = 3.0V
5.1
OUTPUT VOLTAGE (V)
200
VIN = 3.3V
5.6
MAX8969 toc08
0
VIN = 3.7V
70
5.7
VIN = 2.5V
4.60
3.2
VIN = 4.0V
OUTPUT CURRENT (mA)
4.65
VIN = 3.6V
VIN = 4.2V
75
60
OUTPUT VOLTAGE (V)
VIN = 3.2V
3.8
5.00
OUTPUT VOLTAGE (V)
VIN = 4.3V
VIN = 2.5V
VIN = 4.5V
80
1000
LOAD CURRENT (mA)
4.2
3.4
10
LOAD CURRENT (mA)
4.4
4.0
L = TOKO DFE252012 1µH
60
1000
100
85
65
MAX8969 toc05
84
OUTPUT VOLTAGE (V)
90
OUTPUT VOLTAGE (V)
92
toc03
95
90
94
86
OUTPUT VOLTAGE (V)
VIN = 4.3V
95
EFFICIENCY (%)
EFFICIENCY (%)
96
100
MAX8969 toc02
VIN = 3.1V
98
100
MAX8969 toc01
100
EFFICIENCY vs. OUTPUT CURRENT
(VOUT = 5.5V)
EFFICIENCY vs. OUTPUT CURRENT
(VOUT = 5V)
EFFICIENCY vs. OUTPUT CURRENT
(VOUT = 3.7V)
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
Maxim Integrated │ 6
MAX8969
Step-Up Converter for Handheld Applications
Typical Operating Characteristics (continued)
(VIN = 3.6V, COUT = 22µF, X5R, 6.3V local and 10µF, X5R, 6.3V, 1µH inductor, circuit of Figure 1, TA = +25°C, unless otherwise noted.)
3.7V LINE TRANSIENT
5V LINE TRANSIENT
MAX8969 toc11
MAX8969 toc10
3V
VIN
3.7V
2.6V
VIN
AC-COUPLED
100mV/div
VOUT
3.3V
AC-COUPLED
100mV/div
VOUT
TREN = VIN, IOUT = 200mA
TREN = VIN, IOUT = 200mA
100µs/div
100µs/div
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
3.7V LOAD TRANSIENT (0mA-50mA-0mA)
MAX8969 toc13
MAX8969 toc12
MAXIMUM OUTPUT CURRENT (mA)
3000
VOUT, 5V ≥ 4.5V
2500
AC-COUPLED
50mV/div
VOUT
2000
VLX
1500
1000
5V/div
0
50mA
VOUT, 3.7V ≥ 3.35V
IOUT
0
VIN = 2.6V
500
2.5
3.0
3.5
4.0
4.5
5.0
5.5
200µs/div
INPUT VOLTAGE (V)
5V LOAD TRANSIENT (0mA-50mA-0mA)
LIGHT-LOAD RIPPLE
MAX8969 toc15
MAX8969 toc14
AC-COUPLED
50mV/div
VOUT
VLX
5V/div
0
AC-COUPLED
20mV/div
VOUT
2V/div
VLX
50mA
0
IOUT
IOUT = 1mA, VIN = 3.6V
VIN = 3.8V
200µs/div
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0
40µs/div
Maxim Integrated │ 7
MAX8969
Step-Up Converter for Handheld Applications
Typical Operating Characteristics (continued)
(VIN = 3.6V, COUT = 22µF, X5R, 6.3V local and 10µF, X5R, 6.3V, 1µH inductor, circuit of Figure 1, TA = +25°C, unless otherwise noted.)
3.7V LOAD TRANSIENT
(50mA-500mA-50mA)
5V LOAD TRANSIENT
(50mA-500mA-50mA)
MAX8969 toc16
MAX8969 toc17
AC-COUPLED
200mV/div
VOUT
5V/div
0
VLX
AC-COUPLED
100mV/div
VOUT
5V/div
0
VLX
500mA
500mA
IOUT
50mA
50mA
IOUT
VIN = 2.8V
VIN = 3.8V
20µs/div
5.5V LOAD TRANSIENT
(50mA-500mA-50mA)
20µs/div
STARTUP (VOUT = 3.7V)
MAX8969 toc19
toc18
100mV/div
(ACCOUPLED)
VOUT
2V/div
VEN
COUT, TYP = 32µF,
TREN = GND,
IOUT = 10mA,
VIN = 2.6V
0
2V/div
5V/div
IOUT
0
VOUT
VLX
50mA
500mA/div
500mA
2V/div
VLX
0
200µs/div
20µs/div
STARTUP (VOUT = 5V)
STARTUP (VOUT = 5.5V)
MAX8969 toc20
toc21
2V/div
2V/div
VEN
COUT, TYP = 32µF,
TREN = GND,
IOUT = 10mA,
VIN = 3.2V
0
2V/div
VOUT
0
VOUT
5V/div
VLX
COUT = 55µF
TREN = GND
IOUT = 10mA
VIN = 3.3V
2V/div
VLX
0
200µs/div
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2V/div
VEN
IIN
1A/div
200µs/div
Maxim Integrated │ 8
MAX8969
Step-Up Converter for Handheld Applications
Typical Operating Characteristics (continued)
(VIN = 3.6V, COUT = 22µF, X5R, 6.3V local and 10µF, X5R, 6.3V, 1µH inductor, circuit of Figure 1, TA = +25°C, unless otherwise noted.)
HARD-SHORT (VOUT = 3.7V)
HARD-SHORT (VOUT = 5V)
MAX8969 toc22
VOUT
MAX8969 toc23
2V/div
VOUT
2V/div
IOUT
0
2A/div
0
0
2A/div
IOUT
VLX
0
2V/div
VIN = 3.2V, 0.1I LOAD
ILX
2V/div
VLX
0
VIN = 3.2V, 0.1I LOAD
2A/div
2A/div
0
ILX
0
0
40µs/div
20µs/div
SHUTDOWN
MAX8969 toc24
VEN
2V/div
0
VOUT
2V/div
VLX
0
2V/div
0
10I LOAD, TREN = GND
2µs/div
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Maxim Integrated │ 9
MAX8969
Step-Up Converter for Handheld Applications
Pin Configuration
TOP VIEW
(BUMP SIDE DOWN)
MAX8969
1
2
3
A
OUT1
OUT2
IN
B
LX1
LX2
EN
C
GND1
GND2
TREN
+
WLP
(1.25mm × 1.25mm)
Pin Description
PIN
NAME
A1
OUT1
A2
OUT2
A3
IN
B1
LX1
B2
LX2
B3
EN
C1
GND1
C2
GND2
C3
TREN
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FUNCTION
Power Output. Bypass OUT_ to ground with a 22µF rated ceramic capacitor. For optimal
performance place the ceramic capacitor as close as possible to OUT_. OUT1 and OUT2
should be shorted together directly under the IC. In True Shutdown, the output voltage can fall
to 0V, but OUT_ has a diode with its cathode connected to IN. See Figure 3. Connect OUT1 and
OUT2 together directly under the IC.
Input Supply Voltage. Bypass IN to GND_ with a 4.7µF ceramic capacitor. A larger capacitance
may be required to reduce noise.
Converter Switching Node. Connect a 1µH inductor from LX_ to IN. LX_ is high impedance in
shutdown. Connect LX1 and LX2 together directly under the IC. Connect LX1 and LX2 together
directly under the IC.
Enable Input. Drive EN logic-high to enable boost mode, regardless of the logic level of TREN.
Connect EN to ground or drive logic-low to allow TREN to select either True Shutdown or track
mode. See Table 1.
Ground. Connect GND_ to a large ground plane. Connect GND1 and GND2 together directly
under the IC.
Track Enable Input. Drive TREN logic-high to enable track mode. Connect TREN to ground or
drive logic-low to place the IC in True Shutdown. See Table 1.
Maxim Integrated │ 10
MAX8969
Step-Up Converter for Handheld Applications
OUT_
COUT
22µF
MAX8969
IN
REFERENCE
CIN
4.7µF
RAMP
GENERATOR
ATM
COMPARATOR
IN
IN
P1
ATM
0.95 x
TRACK
VOUT_TARGET
CONTROL
LOGIC
PWM
LOGIC
TRUE
SHUTDOWN
N1
ENABLE
TREN
CURRENT
LIMIT
EN
GND_
L1
1µH
LX_
Figure 1. Functional Diagram
Detailed Description
The MAX8969 is a step-up DC-DC switching converter
that utilizes a fixed-frequency PWM architecture with True
Shutdown. With an advanced voltage-positioning control
scheme and high 3MHz switching frequency, the IC is inexpensive to implement and compact, using only a few small
easily obtained external components. Under light-load
conditions, the IC switches only when needed, consuming only 45µA (typ) of quiescent current. The IC is highly
efficient with an internal switch and synchronous rectifier.
Shutdown typically reduces the quiescent current to 1µA
(typ). Low quiescent current and high efficiency make this
device ideal for powering portable equipment.
Internal soft-start limits inrush current to less than 480mA
(typ), while output voltage is less than input voltage. Once
output voltage approaches input voltage approaches
input voltage after a brief delay, output voltage is boosted
to its final value at a rate of approximately 25mV/µs.
During this period, as well as being limited by the voltage,
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ramp rate current is limited by the normal 2.6A boost
mode current limit.
In boost mode, the step-up converter boosts to
VOUT_TARGET from battery input voltages ranging from
2.5V to VOUT_TARGET. When the input voltage ranges
from 0.95 x VOUT_TARGET to 5.5V, the IC enters ATM
and the output voltage approximately follows the input
voltage. During boost mode, the input current limit is set
to 2.6A to guarantee delivery of the rated out current (e.g.,
1A output current when boosting from a 2.5V input supply
to a 3.7V output).
Control Scheme
The step-up converter uses a load/line control scheme.
The load/line control scheme allows the output voltage
to sag under load, but prevents overshoot when the
load is suddenly removed. The load/line control scheme
reduces the total range of voltages reached during transients at the expense of DC output impedance.
Maxim Integrated │ 11
MAX8969
Step-Up Converter for Handheld Applications
UVLO, EXCESSIVE
TEMPERATURE,
OR SHORT CIRCUIT
FROM ANY STATE
TRUE SHUTDOWN
N1 = OFF
P1 = OFF
IQ = 1µA (typ)
EN = 1, OR
TREN = 1
0 = VIN
< VATM
VIN
COMPARATOR
1 = VIN
> VATM
EN = 0,
TREN = 0
EN = 0,
TREN = 0
AUTOMATIC TRACK
MODE (ATM)*
TRACK MODE*
VOUT < VIN,
TREN = 0
N1 = OFF
P1 = CURRENTLIMITED SWITCH
IQ = 30µA (typ)
VOUT < VIN,
TREN = 1
EN = 1,
VOUT > (VIN - 300mV)
BOOST EXIT MODE
N1 = OFF
P1 = OFF
IC WAITS UNTIL
VOUT = VIN
N1 = OFF
P1 = CURRENTLIMITED SWITCH
IQ = 65µA (typ)
BOOST CIRCUITRY ENABLED
EN = 0
BOOST SOFT-START
N1 = SWITCHING
P1 = OFF
EN = 0
VIN
COMPARATOR = 0
(tATM_EXIT)
OUTPUT
BELOW TARGET
[VOUT < (0.72 x
VOUT_TARGET)]
VIN
COMPARATOR = 1
(tATM_ENTER)
SOFT-START
VOLTAGE RAMP
COMPLETE
BOOST MODE
N1 = SWITCHING
P1 = SWITCHING
VOUT = VOUT_TARGET
IQ = 45µA (SKIP MODE)
*EN TAKES PRIORITY OVER TREN. SEE TABLE 1.
Figure 2. State Diagram
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Maxim Integrated │ 12
MAX8969
Step-Up Converter for Handheld Applications
TRUE SHUTDOWN:
P1 BODY DIODE
LX_
OUT_
IN
N1 = OFF
P1 = OFF
TRACK/ATM MODE:
P1 BODY DIODE
LX_
OUT_
IN
N1 = OFF
P1 = CURRENTLIMITED SWITCH
BOOST SOFT-START:
P1 BODY DIODE
LX_
OUT_
IN
N1 = SWITCHING
P1 = OFF
BOOST MODE:
P1 BODY DIODE
LX_
OUT_
IN
N1 = SWITCHING
P1 = SWITCHING
BOOST EXIT MODE:
P1 BODY DIODE
LX_
OUT_
IN
N1 = OFF
P1 = OFF
Figure 3. Modes of Operation
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Maxim Integrated │ 13
MAX8969
Step-Up Converter for Handheld Applications
The IC is designed to operate with the input voltage range
straddling its output voltage set point. Two techniques are
used to accomplish this. The first technique is to activate
ATM if the input voltage exceeds 95% of the output set
point; see the Automatic Track Mode (ATM) section. The
second technique is automatic frequency adjustment.
•
In track and ATM, current is limited to prevent
excessive inrush current during soft-start and to
protect against overload conditions. If the die temperature exceeds +165°C in track/ATM, the switch
turns off until the die temperature has cooled to
+145°C.
Automatic Track Mode (ATM)
•
In boost mode, during each 3MHz switching cycle,
if the inductor current exceeds 2.6A, the n-channel
MOSFET is shut off and the p-channel MOSFET is
switched on. The end result is that LX_ current is
regulated to 2.6A or less. A 2.6A inductor current is a
large enough current to guarantee a 1A output load
current under all intended operating conditions. The
IC can operate indefinitely while regulating the inductor current to 2.6A or less.
ATM is entered when an internal comparator signals that
the input voltage has exceeded the ATM threshold. The
ATM threshold is 95% of the output voltage target. At this
point, the IC enters ATM, with the pMOS switch turned on,
regardless of the status of TREN. Note that EN must be
high to enable ATM mode. This behavior is summarized
in Table 1.
Automatic Frequency Adjustment
Automatic frequency adjustment is used to maintain
stability if the input voltage is above 80% and below
95% of the output set point. Frequency adjustment is
required because the n-channel has a minimum on-time
of approximately 60ns. At 3MHz, this would lead to the
p-channel having a maximum duty factor of 82%. With
an input voltage more than 82% of the output set point,
the p-channel’s duty factor must be increased by reducing operating frequency either through cycle skipping or
adjusting the clock’s frequency. The IC adjusts its clock
frequency rather than simply skipping cycles. This adjustment is done in two steps. The first step occurs if the input
voltage exceeds approximately 83% of the output voltage
and reduces clock speed to approximately 1.6MHz. The
second step occurs if the input voltage is greater than
output voltage less 460mV. If this condition is met, clock
frequency is reduced to approximately 1MHz. Frequency
adjustment allows the converter to operate at a known
frequency under all conditions.
Fault Protection
In track, ATM, and boost modes, the IC has protection
against overload and overheating.
However, if a short circuit or extremely heavy load is
applied to the output, the output voltage decreases since
the inductor current is limited to 2.6A.
If the output voltage decreases to less than 72% of the
regulation voltage target (i.e., 2.8V with VOUT_TARGET
of 3.7V), a short circuit is assumed, and the IC returns to
the shutdown state. The IC then attempts to start up if the
output short is removed. Even if the output short persists
indefinitely, the IC thermal protection ensures that the die
is not damaged.
Applications where the power source can be disconnected from the VIN must ensure that the VOUT is fully
discharged before reconnecting the power source.
True Shutdown
During operation in boost mode, the p-channel MOSFET
prevents current from flowing from OUT_ to LX_. In all
other modes of operation, it is desirable to block current
flowing from LX_ to OUT_. True Shutdown prevents current from flowing from LX_ to OUT_ while the IC is shut
down by reversing the internal body diode of the p-channel
MOSFET. This feature is also active during track/ATM to
allow current limit to function as anticipated.
Table 1. Modes of Operation
VIN COMPARATOR
EN
TREN
X
0
0
True Shutdown
X
0
1
Track
0 = VIN < VATM
1
X
Boost
1
X
ATM
1 = VIN > VATM
MODE OF OPERATION
X = Don't care.
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Maxim Integrated │ 14
MAX8969
Step-Up Converter for Handheld Applications
Upon leaving boost mode, the p-channel MOSFET continues to prevent current from flowing from OUT_ to LX_
until OUT_ and IN are approximately the same voltage.
After this condition has been met, track/ATM and shutdown operate normally.
Thermal Considerations
In most applications, the IC does not dissipate much heat
due to its high efficiency. But in applications where the IC
runs at high ambient temperature with heavy loads, the
heat dissipated may cause the temperature to exceed the
maximum junction temperature of the part. If the junction
temperature reaches approximately +165°C, the thermal
overload protection is activated.
The maximum power dissipation depends on the
thermal resistance of the IC package and circuit board.
The power dissipated (PD) in the device is:
PD = POUT x (1/η - 1)
where η is the efficiency of the converter and POUT is
the output power of the step-up converter. The maximum
allowed power dissipation is:
PMAX = (TJMAX - TA)/θJA
where (TJMAX - TA) is the temperature difference between
the IC’s maximum rated junction temperature and the surrounding air, and θJA is the thermal resistance of the junction through the PCB, copper traces, and other materials
to the surrounding air.
Applications Information
Step-Up Inductor Selection
Due to the small size of the recommended capacitor, the
inductor’s value is limited to approximately 1µH. Inductors
of approximately 1µH guarantee stable operation of the
converter with capacitance as small as 8µF (actual) present
on the converter’s output. If the inductor’s value is reduced
significantly below 1µH, ripple can become excessive.
Output Capacitor Selection
An output capacitor (COUT) is required to keep the
output-voltage ripple small and to ensure regulation loop
stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors
are highly recommended due to their small size and low
www.maximintegrated.com
ESR. Ceramic capacitors with X5R or X7R temperature
characteristics generally perform well. One 22µF (with
a minimum actual capacitance of 6µF under operating
conditions) is recommended. This capacitor along with
an additional 10µF of bypass capacitance, associated
with the load, guarantee proper performance of the IC.
The minimum combined capacitance is required to be
8µF or larger. These capacitors can be found with case
size 0603 or larger.
Input Capacitor Selection
The input capacitor (CIN) reduces the current peaks
drawn from the battery or input power source. The
impedance of CIN at the switching frequency should
be kept very low. Ceramic capacitors with X5R or X7R
temperature characteristics are highly recommended
due to their small size, low ESR, and small temperature
coefficients. Note that some ceramic dielectrics exhibit
large capacitance and ESR variation with temperature
and DC bias. Ceramic capacitors with Z5U or Y5V
temperature characteristics should be avoided. A 4.7µF
input capacitor is recommended for most applications.
This assumes that the input power source has at least
22µF of additional capacitance near the IC. For optimum
noise immunity and low input-voltage ripple, the input
capacitor value can be increased.
Output Current
The device supports a peak output current of 1A.
Continuous operation with 1A output current at elevated
temperature is not guaranteed. With sustained high
current (> 100ms, > 1A), the junction temperature (TJ)
rises to the thermal shutdown threshold. The electrical
characteristics table lists Minimum Continuous Output
Current values that represent what the typical operating
circuit can achieve when considering device and component variations. Note that a typical part on the EV kit can
achieve more current than listed. The listed currents are
calculations that consider normal variation for inductor
DCR, inductance, input and output capacitor ESR, switching frequency, MOSFET RDSON, thermal effects, and
LX_ nMOS. To calculate the Minimum Continuous Output
Currents for a given system, refer to the spreadsheet
calculator.
Maxim Integrated │ 15
MAX8969
Step-Up Converter for Handheld Applications
Recommended PCB Layout and Routing
Poor layout can affect the IC performance, causing electromagnetic interference (EMI) and electromagnetic compatibility (EMC) performance, ground bounce, and voltage
losses. Poor layout can also affect regulation and stability.
A good layout is implemented using the following rules:
•
Place the inductor, input capacitor, and output capacitor close to the IC using short traces. These components carry high switching frequencies and large
traces act like antennas. The output capacitor placement is the most important in the PCB layout and
should be placed directly next to the IC. The inductor
and input capacitor placement are secondary to the
output capacitor’s placement but should remain close
to the IC.
•
Route the output voltage path away from the inductor
and LX_ switching node to minimize noise and magnetic interference.
•
Maximize the size of the ground metal on the component side to help with thermal dissipation. Use
a ground plane with several vias connecting to the
component-side ground to further reduce noise interference on sensitive circuit nodes.
Chip Information
PROCESS: BiCMOS
Ordering Information
PART
VOUT
(V)
TEMP RANGE
PINPACKAGE
MAX8969EWL33+
3.3
-40°C to +85°C
9 WLP
MAX8969EWL35+
3.5
-40°C to +85°C
9 WLP
MAX8969EWL37+
3.7
-40°C to +85°C
9 WLP
MAX8969EWL42+
4.25
-40°C to +85°C
9 WLP
MAX8969EWL50+
5.0
-40°C to +85°C
9 WLP
MAX8969EWL53+
5.3
-40°C to +85°C
9 WLP
MAX8969EWL55+
5.5
-40°C to +85°C
9 WLP
Note: The output voltage range is from 3.3V to 5.5V. Contact
the factory for output options and availability.
+Denotes a lead(Pb)-free/RoHS-compliant package.
Refer to the MAX8969 Evaluation Kit for more details.
www.maximintegrated.com
Maxim Integrated │ 16
MAX8969
Step-Up Converter for Handheld Applications
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PACKAGE TYPE
PACKAGE CODE
OUTLINE NO.
LAND PATTERN NO.
9 WLP
W91B1+7
21-0459
Refer to Application Note 1891
E
PIN 1
INDICATOR
MARKING
1
COMMON DIMENSIONS
A3
A
A1
AAAA
D
A2
A
0.05 S
S
See Note 7
SIDE VIEW
TOP VIEW
E1
A
0.64
0.05
A1
0.19
0.03
0.45 REF
A2
0.025 BASIC
A3
b
0.27
0.03
D1
0.80
BASIC
E1
0.80
BASIC
e
0.40 BASIC
SD
0.00 BASIC
SE
0.00 BASIC
SE
e
B
C
SD
B
D1
A
1
2
3
A
b
0.05 M
S
DEPOPULATED
BUMPS
E
D
W91B1+7
1.260 0.040
1.260 0.040
NONE
W91C1+1
1.595 0.035
1.415 0.035
NONE
W91F1+1
1.435 0.015
1.345 0.015
NONE
W91G1+1
1.465 0.015
1.455 0.015
NONE
W91J1+1
1.238 0.015
1.238 0.015
NONE
PKG. CODE
AB
BOTTOM VIEW
NOTES:
1. Terminal pitch is defined by terminal center to center value.
2. Outer dimension is defined by center lines between scribe lines.
3. All dimensions in millimeter.
4. Marking shown is for package orientation reference only.
5. Tolerance is ± 0.02 unless specified otherwise.
6. All dimensions apply to PbFree (+) package codes only.
7. Front - side finish can be either Black or Clear.
- DRAWING NOT TO SCALE -
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maxim
integrated
TITLE
APPROVAL
TM
PACKAGE OUTLINE
9 BUMPS, WLP PKG. 0.4mm PITCH
DOCUMENT CONTROL NO.
21-0459
REV.
G
1
1
Maxim Integrated │ 17
MAX8969
Step-Up Converter for Handheld Applications
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
9/11
Initial release
—
1
5/12
Updated Electrical Characteristics table
2
2
5/15
Updated Benefits and Features section
1
3
3/16
Updated General Description, Ordering Information, Absolute Maximum Ratings,
Package Thermal Characteristics, Electrical Characteristics, Typical Operating
Characteristics, Pin Description, Detailed Description, Output Capacitor Selection
sections, Figure 2, Table 1, and added Output Current section
4
1/18
Updated Electrical Characteristics table and Applications Information section
5
3/18
Added 5.3V information to Electrical Characteristics and Ordering Information tables
and removed 5.7V output option
6
3/18
Corrected typo in Electrical Characteristics table
3
7
4/20
Updated Fault Protection section
14
1–12, 14–17
4, 15
1–5, 16
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
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