19-4663; Rev 0; 5/09
KIT
ATION
EVALU
BLE
AVAILA
Dual PWM Step-Down Converter in a 2mm x
2mm Package for WCDMA PA and RF Power
General Description
The MAX8896 dual step-down converter is optimized
for powering the power amplifier (PA) and RF transceiv-
er in WCDMA handsets. This device integrates a high-
efficiency PWM step-down converter (OUT1) for
medium and low-power transmission, and a 140mΩ
(typ) bypass FET to power the PA directly from the bat-
tery during high-power transmission. A second high-
efficiency PWM step-down converter (OUT2) supplies
power directly to a high PSRR, low output noise, 200mA
low-dropout linear regulator (LDO) to power the RF
transceiver.
Fast switching allows the use of small ceramic input and
output capacitors while maintaining low ripple voltage.
The feedback network is integrated reducing external
component count and total solution size. OUT1 uses an
analog input driven by an external DAC to control the
output voltage linearly for continuous PA power adjust-
ment. At high duty cycle, OUT1 automatically switches to
bypass mode, connecting the input to the output through
a low-impedance (140mΩ, typ) MOSFET.
OUT2 is a 2MHz fixed-frequency, step-down converter
capable of operating at 100% duty cycle. Output accu-
racy is ±2% over load, line, and temperature. The out-
put of OUT2 is preset to 3.1V to provide power to a
200mA, 2.8V LDO designed for low noise (16µV
RMS
,
typ), high PSRR (65dB, typ) operation. This configura-
tion provides noise attenuation for the RF transceiver
power supply in the 100Hz to 100kHz range.
Other features include separate output enables, low-
supply current shutdown, output overcurrent, and
overtemperature protection. The MAX8896 is available
in a 16-bump, 2mm x 2mm UCSP™ package (0.7mm
max height).
Features
o
PA Step-Down Converter (OUT1)
7.5µs (typ) Settling Time for 0.5V to 1V Output
Voltage Change
Dynamic Output Voltage Setting from 0.5V to
V
BATT
140mΩ Bypass PFET and 100% Duty Cycle
for Low Dropout
2MHz Switching Frequency
Low Output Voltage Ripple
700mA (min) Output Drive Capability
2% Gain Accuracy
Tiny External Components
o
RF Step-Down Converter (OUT2)
2MHz Fixed Switching Frequency
94% Peak Efficiency
100% Duty Cycle
2% Output Accuracy Over Load, Line, and
Temperature
200mA (min) Output Drive Capability
Tiny External Components
o
Low-Noise LDO
Guaranteed 200mA Output
High 65dB (typ) PSRR
Fixed Output Voltage
Low Noise (16µV
RMS
, typ)
o
Simple Logic ON/OFF Controls
o
Low 0.1µA Shutdown Current
o
2.7V to 5.5V Supply Voltage Range
o
Thermal Shutdown
o
2mm x 2mm UCSP Package (4 x 4 Grid)
MAX8896
Applications
WCDMA/NCDMA Cellular Handsets
Smartphones
PART
MAX8896EREE+T
Ordering Information
PIN-PACKAGE
16 UCSP (0.5mm pitch)
LDO
VOLTAGE
2.80V
Note:
Device operates over the -40°C to +85°C temperature
range.
+Denotes
a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
UCSP is a trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.
1
________________________________________________________________
Maxim Integrated Products
For information on other Maxim products, visit Maxim’s website at www.maxim-ic.com.
Dual PWM Step-Down Converter in a 2mm x
2mm Package for WCDMA PA and RF Power
MAX8896
ABSOLUTE MAXIMUM RATINGS
V
CC
, IN1, IN2, PAEN, RFEN1, RFEN2,
REFIN, OUT2, REFBP to AGND .........................-0.3V to +6.0V
PAOUT to AGND........................................-0.3V to (V
IN1
+ 0.3V)
LDO to AGND .........................................-0.3V to (V
OUT2
+ 0.3V)
IN1, IN2 to V
CC
......................................................-0.3V to +0.3V
IN1 to IN2 ..............................................................-0.3V to +0.3V
PGND1, PGND2 to AGND.....................................-0.3V to +0.3V
LX1 Current .......................................................................1A
RMS
LX2 Current .......................................................................1A
RMS
IN1 and PAOUT Current....................................................1A
RMS
PAOUT, OUT2, LDO Short Circuit to PGND1,
PGND2 ....................................................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
16-Bump UCSP (derate 12.5mW/°C above +70°C) ............1W
Junction-to-Ambient Thermal Resistance (θ
JA
) (Note 1)...96°C/W
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Bump Temperature (soldering, reflow) ...........................+260°C
Note 1:
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.maxim-ic.com/thermal-tutorial.
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.
ELECTRICAL CHARACTERISTICS
(V
CC
= V
IN1
= V
IN2
= V
PAEN
= V
RFEN1
= V
RFEN2
= 3.6V, V
REFIN
= 0.72V, T
A
= -40°C to +85°C, typical values are at T
A
= +25°C,
unless otherwise noted.) (Note 2)
PARAMETER
INPUT SUPPLY
Input Voltage
Input Undervoltage Threshold
Shutdown Supply Current
LOGIC CONTROL
PAEN, RFEN1, RFEN2 Logic
Input High Voltage
PAEN, RFEN1, RFEN2 Logic
Input Low Voltage
PAEN, RFEN1, RFEN2 Internal
Pulldown Resistor
PAEN, RFEN1, RFEN2 Logic
Input Current
REFBP
REFBP Output Voltage
THERMAL PROTECTION
Thermal Shutdown
OUT1
Quiescent Supply Current
On-Resistance
Load Regulation
LX1 Leakage Current
VRFEN1 = VRFEN2 = 0V, IPA = 0A,
no switching
p-channel MOSFET switch, I
LX1
= -200mA
n-channel MOSFET rectifier, I
LX1
= 500mA
R
L
is the inductor resistance
V
IN1
= 5.5V, V
LX1
= 0V
T
A
= +25°C
T
A
= +85°C
155
0.16
0.17
R
L
/2
0.1
1
5
0.40
0.40
µA
Ω
V/A
µA
T
A
rising, 20°C typical hysteresis
+160
°C
0µA
≤
IREFBP
≤
1µA
1.237
1.250
1.263
V
V
IL
= 0
T
A
= +25°C
T
A
= +85°C
2.7V
≤
V
CC
≤
5.5V
2.7V
≤
V
CC
≤
5.5V
400
800
0.01
0.1
1.3
0.4
1600
1
V
V
kΩ
µA
V
CC
, V
IN1,
V
IN2
V
CC
rising, 180mV typical hysteresis
V
PAEN
= V
RFEN1
= V
RFEN2
= 0
T
A
= +25°C
T
A
= +85°C
2.7
2.52
2.63
0.1
0.1
5.5
2.70
4
V
V
µA
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
Dual PWM Step-Down Converter in a 2mm x
2mm Package for WCDMA PA and RF Power
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= V
IN1
= V
IN2
= V
PAEN
= V
RFEN1
= V
RFEN2
= 3.6V, V
REFIN
= 0.72V, T
A
= -40°C to +85°C, typical values are at T
A
= +25°C,
unless otherwise noted.) (Note 2)
PARAMETER
Peak Current Limit (p-Channel
MOSFET)
Valley Current Limit (n-Channel
MOSFET)
Minimum On-Time
Minimum Off-Time
Power-Up Delay
OUT1 REFIN
Common-Mode Range
REFIN-to-PAOUT Gain
Input Resistance
BYPASS
Bypass Mode Threshold
On-Resistance
Bypass Current Limit
Step-Down Current Limit in
Bypass
Total Bypass Current Limit
Bypass Off-Leakage Current
OUT2
Output Voltage
OUT2 Leakage Current
No-Load Supply Current
On-Resistance
p-Channel Current-Limit
Threshold
n-Channel Negative Current Limit
Maximum Duty Cycle
Minimum Duty Cycle
PWM Frequency
Power-Up Delay
From V
RFEN1
or V
RFEN2
rising to V
LX2
rising
1.8
I
OUT2
= 0 to 150mA,
V
IN2
= V
CC
= 3.2V to 4.5V
V
RFEN1
= V
RFEN2
= 0
T
A
= +25°C
T
A
= +85°C
3.038
3.1
0.01
0.1
2.5
300
300
400
450
400
100
16.5
2.0
35
2.2
75
500
3.162
5
V
µA
mA
mΩ
mΩ
mA
mA
%
%
MHz
µs
V
PAOUT
= V
LX1
= 1.5V
V
CC
= V
IN1
= 5.5V,
V
PAOUT
= 0V
T
A
= +25°C
T
A
= +85°C
V
REFIN
falling, 150mV hysteresis
p-channel MOSFET
I
OUT
= -90mA
V
PAOUT
= 1.5V
T
A
= +25°C
T
A
= +85°C
700
1200
1900
0.396
xV
CC
0.14
0.3
1000
1450
2450
0.01
1
1400
1700
3100
5
V
Ω
mA
mA
mA
µA
V
REFIN
= 0.32V or 1.32V, I
LX1
= 0A
0.2
2.45
2.5
320
1.7
2.55
kΩ
V
From V
PAEN
rising to V
LX1
rising
CONDITIONS
MIN
1200
1100
TYP
1450
1350
70
50
50
75
MAX
1700
1600
UNITS
mA
mA
ns
ns
µs
MAX8896
V
PAEN
= 0V, I
OUT2
= 0A, switching
p-channel MOSFET switch, I
LX2
= -40mA
n-channel MOSFET rectifier, I
LX2
= 40mA
_______________________________________________________________________________________
3
Dual PWM Step-Down Converter in a 2mm x
2mm Package for WCDMA PA and RF Power
MAX8896
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= V
IN1
= V
IN2
= V
PAEN
= V
RFEN1
= V
RFEN2
= 3.6V, V
REFIN
= 0.72V, T
A
= -40°C to +85°C, typical values are at T
A
= +25°C,
unless otherwise noted.) (Note 2)
PARAMETER
LDO
Output Voltage, V
LDO
Current Limit
Dropout Voltage
Line Regulation
Load Regulation
Power-Supply Rejection
∆V
LDO
/∆V
OUT2
Output Noise
Minimum Output Capacitance for
Stable Operation
Output Leakage Current
Power-Up Delay
V
OUT2
= 3.1V, I
LDO
= 1mA to 200mA
V
OUT2
= 3.1V, V
LDO
= 0V
V
OUT2
= 3.1V, I
LDO
= 100mA
V
OUT2
stepped from 3.5V to 5.5V, I
LDO
= 100mA
V
OUT2
= 3.1V, I
LDO
stepped from 50µA to 200mA
V
OUT2
= 3.1V, 10Hz to 10kHz,
C
LDO
= 1µF, I
LDO
= 100mA
100Hz to 100kHz,
C
LDO
= 1µF, I
LDO
= 100mA
0 < I
LDO
< 200mA
V
OUT2
= 3.1V, V
RFEN1
= V
RFEN2
= 0V
From V
RFEN1
or V
RFEN2
rising to V
LDO
rising
2.744
250
2.800
420
70
2.4
25
65
16
1
25
50
2.856
750
V
mA
mV
mV
mV
dB
µV
RMS
µF
nA
µs
CONDITIONS
MIN
TYP
MAX
UNITS
Note 2:
All devices are 100% production tested at T
A
= +25°C. Limits over the operating temperature range are guaranteed by
design.
4
_______________________________________________________________________________________
Dual PWM Step-Down Converter in a 2mm x
2mm Package for WCDMA PA and RF Power
Typical Operating Characteristics
(V
CC
= V
IN1
= V
IN2
= 3.6V, V
REFIN
= 0.72V, circuit of Figure 3, T
A
= +25°C, unless otherwise noted.)
OUT1 PA STEP-DOWN CONVERTER
EFFICIENCY vs. LOAD CURRENT
V
PA
= 3.18V
MAX8896 toc03
MAX8896 oc02
MAX8896
OUT1 PA BYPASS MODE DROPOUT
VOLTAGE vs. PA LOAD CURRENT
MAX8896 toc01
OUT1 PA STEP-DOWN CONVERTER
EFFICIENCY vs. OUTPUT VOLTAGE
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
V
IN1
= 3.2V
V
IN1
= 4.2V
V
IN1
= 3.6V
EFFICIENCY (%)
R
PA
= 7.5Ω
70
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
100
90
85
80
75
BYPASS MODE
100
95
80
70
DROPOUT VOLTAGE (mV)
60
50
40
30
20
10
0
0
100
200
300
400
500
600
V
IN1
= 4.2V
V
IN1
= 3.2V
V
IN1
= 3.6V
10
0
700
LOAD CURRENT (mA)
200
300
400
500
600
700
OUTPUT VOLTAGE (V)
LOAD CURRENT (mA)
OUT1 PA STEP-DOWN CONVERTER
EFFICIENCY vs. LOAD CURRENT
V
PA
= 2.58V
MAX8896 toc04
OUT1 PA STEP-DOWN CONVERTER
EFFICIENCY vs. LOAD CURRENT
V
PA
= 1.58V
MAX8896 toc05
OUT1 PA STEP-DOWN CONVERTER
EFFICIENCY vs. LOAD CURRENT
V
PA
= 1.18V
MAX8896 toc06
100
95
EFFICIENCY (%)
90
85
80
75
70
50
150
250
350
450
550
100
95
EFFICIENCY (%)
90
85
80
75
70
100
95
EFFICIENCY (%)
90
85
80
75
70
650
50
150
250
350
450
50
150
LOAD CURRENT (mA)
250
LOAD CURRENT (mA)
LOAD CURRENT (mA)
MAX8896 toc07
MAX8896 toc08
95
90
EFFICIENCY (%)
85
80
75
70
65
60
25
75
125
175
95
90
EFFICIENCY (%)
85
80
75
70
65
60
1.88
1.86
OUTPUT VOLTAGE (V)
1.84
1.82
1.80
1.78
1.76
1.74
1.72
1.70
R
L
= 0.09Ω
225
25
75
125
175
225
0
100
200
300
400
500
600
700
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
_______________________________________________________________________________________
MAX8896 toc09
100
OUT1 PA STEP-DOWN CONVERTER
EFFICIENCY vs. LOAD CURRENT
V
PA
= 0.77V
100
OUT1 PA STEP-DOWN CONVERTER
EFFICIENCY vs. LOAD CURRENT
V
PA
= 0.56V
OUT1 PA STEP-DOWN CONVERTER
OUTPUT VOLTAGE vs. LOAD CURRENT
1.90
5
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