MAX8836ZEREEE+T [MAXIM]
1.2A PWM Step-Down Converter in 2mm x 2mm WLP/UCSP for PA Power;
| 型号： | MAX8836ZEREEE+T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 1.2A PWM Step-Down Converter in 2mm x 2mm WLP/UCSP for PA Power |
| 文件： | 总19页 (文件大小：420K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4059; Rev 1; 9/08
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
MAX836Z
General Description
Features
The MAX8836Z high-frequency step-down converter is
optimized to provide a fixed output voltage with ultra-
low dropout. The device integrates a high-efficiency
PWM step-down converter for medium- and low-power
transmission, and a 60mΩ typical bypass FET for ultra
low-dropout operation. A 200mA low-noise, high-PSRR
low-dropout regulator (LDO) is also integrated.
o PA Step-Down Converter
Selectable Output Voltage (3.1V or 3.4V)
25µs Settling Time for 3.1V to 3.4V Change
OUT
60mΩ PFET at 100% Duty-Cycle for Low
Dropout
Low Output Voltage Ripple
1.2A Output Drive Capability
2% Output Voltage Accuracy
Tiny External Components
Fast-switching allows the use of small ceramic input and
output capacitors while maintaining low ripple voltage.
The feedback network is integrated, further reducing
external component count and total solution size. At high
duty cycle, the MAX8836Z automatically switches to the
bypass mode, connecting the input to the output
through a low-impedance (60mΩ typ) MOSFET. The
LDO in the MAX8836Z is designed for low-noise opera-
o Low-Noise LDO
Low 35µV
(typ) Output Noise
RMS
High 65dB (typ) PSRR
Guaranteed 200mA Output Current Drive
Capability
ON/OFF Control
tion (35µV
typ). Both the PWM step-down and LDO
are individually enabled through separate logic-control
interfaces.
RMS
o Low 0.1µA Shutdown Current
o 2.7V to 5.5V Supply Voltage Range
o Thermal Shutdown
The MAX8836Z is available in 16-bump, 2mm x 2mm
WLP and UCSP™ packages (0.7mm max height).
o Tiny 2mm x 2mm x 0.7mm WLP and UCSP
Packages (4 x 4 Grid)
Applications
WCDMA/NCDMA Cellular Handsets
Typical Operating Circuit
Wireless PDAs
Smartphones
OUTPUT
3.1V OR 3.4V
INPUT
Li+ BATTERY
IN
PA
LX
Ordering Information
4.7µF
2.2µH
GND
PART
PIN-PACKAGE
TEMP RANGE
4.7µF
16 WLP
(W162B2+1)
MAX8836Z
MAX8836ZEWEEE+T
-40°C to +85°C
HP
SET OUTPUT
ENABLE BUCK
ENABLE LDO
16 UCSP
(R162A2+1)
LDO2
200mA
PA_EN
MAX8836ZEREEE+T
-40°C to +85°C
1µF
EN2
+Denotes a lead-free/RoHS-compliant package.
T = Tape and reel.
REFBP
0.22µF
Pin Configuration appears at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
ABSOLUTE MAXIMUM RATINGS
IN1A, IN1B, IN2, EN2, REFBP to AGND................-0.3V to +6.0V
PAA and PAB Short Circuit to GND or IN...................Continuous
PAA, PAB, PA_EN, HP to AGND....-0.3V to (V
LDO2 to AGND ..........................................-0.3V to (V
IN2 to IN1B/IN1A...................................................-0.3V to +0.3V
PGND to AGND.....................................................-0.3V to +0.3V
LX Current ......................................................................0.7A
IN1A/IN1B and PAA/PAB Current .....................................2A
/V
+ 0.3V)
+ 0.3V)
Continuous Power Dissipation (T = +70°C)
IN1A IN1B
A
16-Bump WLP (derate 12.5mW/°C above +70°C).............1W
16-Bump UCSP (derate 12.5mW/°C above +70°C) ..........1W
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Bump Temperature (soldering, reflow)............................+260°C
IN2
RMS
RMS
Note: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device
can be exposed to during board level solder attach and rework. This limit permits only the use of the solder profiles recom-
mended 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.
MAX836Z
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
= V
= V
= V
= V
= 3.6V, V = 0V, T = -40°C to +85°C. Typical values are at T = +25°C, unless otherwise
IN1A
IN1B
IN2
PA_EN
EN2
HP
A
A
noted.) (Note 1)
PARAMETER
INPUT SUPPLY
Input Voltage
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
, V
, V
2.7
5.5
V
V
IN1A IN1B IN2
Input Undervoltage Threshold
, V
, V
rising, 180mV typical hysteresis
2.52
2.63
800
2.70
IN1A IN1B IN2
HP, PA_EN, EN2 Pulldown
Resistor
400
1600
4
kΩ
T
T
= +25°C
= +85°C
0.1
0.1
A
Shutdown Supply Current
V
= V
= 0V
LDO2
µA
PA_EN
PA_EN
EN2
A
V
V
V
= 0V, I
= 0A
100
3500
180
150
No-Load Supply Current
= 0V, I = 0A, switching
µA
°C
EN2
EN2
PA
= 0V, I = 0A, no switching
PA
THERMAL PROTECTION
Thermal Shutdown
T
rising, 20°C typical hysteresis
+160
A
LOGIC CONTROL
PA_EN, EN2, HP Logic-Input
High Voltage
1.3
V
V
PA_EN, EN2, HP Logic-Input Low
Voltage
0.4
1
T
T
= +25°C
= +85°C
0.01
0.1
A
Logic-Input Current
(PA_EN, EN2, HP)
V
= 0V
µA
IL
A
PA OUTPUT VOLTAGE
HP = 0
HP = 1
3.365
3.010
3.434
3.065
3.503
3.190
I
= 0A, V
= V
LX
IN1A IN1B
Output Voltage
V
V
= V
= 3.9V
IN2
I
x
LX
Output Voltage Load Regulation
R /2
L
2
_______________________________________________________________________________________
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
MAX836Z
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= V
= V
= V
= 3.6V, V = 0V, T = -40°C to +85°C. Typical values are at T = +25°C, unless otherwise
IN1A
IN1B
IN2
PA_EN
EN2
HP
A
A
noted.) (Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
LX
p-channel MOSFET switch, I = -40mA
0.15
0.15
0.1
1
LX
On-Resistance
Ω
n-channel MOSFET rectifier, I = 40mA
LX
T
A
T
A
= +25°C
= +85°C
5
V
V
= V
= 0V
= V
= 5.5V,
IN2
IN1A
IN1B
LX Leakage Current
µA
LX
p-Channel MOSFET Peak
Current Limit
V
= 0V
1.3
1.1
1.5
1.3
1.8
1.6
A
A
LX
n-Channel MOSFET Valley
Current Limit
Minimum On- and Off-Times
Power-Up Delay
BYPASS
0.07
80
µs
µs
From PA_EN rising to LX rising
p-channel MOSFET bypass,
190
0.1
T
T
= +25°C
= +85°C
0.060
0.1
A
On-Resistance
Ω
I
PA
= -90mA
A
Bypass Current Limit
V
V
= 0V
0.8
2.1
1.4
1.8
3.6
A
A
PA
LX
Total Bypass Current Limit
= V = 0V
PA
2.9
0.985 x
Bypass Threshold
V
rising, 150mV hysteresis
V/V
µA
IN2
V
PA
T
T
= +25°C
= +85°C
0.01
0.1
5
A
V
V
= V
= V
= 5.5V,
IN2
IN1A
PAA
IN1B
Bypass Off-Leakage Current
= V
= 0V
PAB
A
LDO2
V
V
= 5.5V, I
= 3.4V, I
= 1mA;
= 1mA
IN2
IN2
LDO2
Output Voltage V
2.765
2.85
2.936
750
V
LDO2
LDO2
Output Current
Current Limit
200
250
mA
mA
mV
mV
mV
V
= 0V
550
70
LDO2
Dropout Voltage
Line Regulation
Load Regulation
I
= 100mA, T = +25°C (V
≥ 2.5V)
LDO2
A
LDO2
V
stepped from 3.5V to 5.5V, I
= 100mA
LDO2
2.4
25
IN2
I
stepped from 50µA to 200mA
LDO2
Power-Supply Rejection
∆V /∆V
10Hz to 10kHz, C
= 1µF, I
= 30mA
65
dB
LDO2
LDO2
LDO2
IN2
Output Noise
100Hz to 100kHz, C
= 1µF, I
= 30mA
35
100
1
µV
RMS
LDO2
LDO2
0 < I
0 < I
< 10mA
nF
µF
kΩ
LDO2
LDO2
Output Capacitor for Stable
Operation
< 200mA
Shutdown Output Impedance
REFBP
V
= 0V
1
EN2
REFBP Output Voltage
REFBP Supply Rejection
0 ≤ I
≤ 1µA
1.237
1.250
0.2
1.263
5
V
REFBP
V
stepped from 2.55V to 5.5V
mV
IN2
Note 1: All devices are 100% production tested at T = +25°C. Limits over the operating temperature range are guaranteed by design.
A
_______________________________________________________________________________________
3
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Typical Operating Characteristics
(V
noted.)
= V
= V
= 3.6V, V = 3.4V, V
= 2.85V, R = 7.5Ω, circuit of MAX8805WEVKIT, T = +25°C, unless otherwise
LDO2 PA A
IN1A
IN1B
IN2
PA
PA STEP-DOWN CONVERTER
EFFICIENCY vs. LOAD CURRENT
PA STEP-DOWN CONVERTER
EFFICIENCY vs. LOAD CURRENT
BYPASS MODE DROPOUT VOLTAGE
vs. PA LOAD CURRENT
100
98
96
94
92
90
88
86
84
82
80
100
98
96
94
92
90
88
86
84
82
80
140
120
100
80
V
= V
= 3.6V
V
= V
= 3.6V
IN1B
IN1A
IN1B
IN1A
MAX836Z
V
= V
= 3.9V
= 4.2V
IN1A
IN1B
V
= V
= 3.9V
IN1B
IN1A
60
V
= V
IN1B
IN1A
40
V
= V
= 4.2V
IN1B
IN1A
100
20
L = 2.2µH
FDK MIPF2520
L = 1µH
FDK MIPF2520
0
10
100
LOAD CURRENT (mA)
1000
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
PA LOAD CURRENT (A)
10
1000
LOAD CURRENT (mA)
PA STEP-DOWN CONVERTER
PA STEP-DOWN CONVERTER
OUTPUT VOLTAGE vs. INPUT VOLTAGE
OUTPUT VOLTAGE vs. LOAD CURRENT
3.5
3.4
3.3
3.2
3.1
3.0
2.9
2.8
2.7
2.6
2.5
3.7
3.6
3.5
3.4
3.3
3.2
3.1
3.0
2.9
2.8
2.7
HP = PGND
HP = PGND
HP = IN1A = IN1B
HP = IN1A = IN1B
2.5
3.0
3.5
4.0
4.5
5.0
5.5
0
200
400
600
800
1000
INPUT VOLTAGE (V)
LOAD CURRENT (mA)
PA STEP-DOWN CONVERTER LIGHT-LOAD
PA STEP-DOWN CONVERTER
HEAVY-LOAD SWITCHING
SWITCHING WAVEFORMS
MAX8836Z toc06
MAX8836Z toc07
50mV/div
AC-COUPLED
50mV/div
AC-COUPLED
V
V
PA
PA
200mA/div
I
LX
I
LX
LX
200mA/div
2V/div
V
V
2V/div
LX
V
= 3.4V, I = 50mA
PA
PA
V
= 3.4V, I = 500mA
PA
PA
1µs/div
1µs/div
4
_______________________________________________________________________________________
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
MAX836Z
Typical Operating Characteristics (continued)
(V
noted.)
= V
= V
= 3.6V, V = 3.4V, V
= 2.85V, R = 7.5Ω, circuit of MAX8805WEVKIT, T = +25°C, unless otherwise
IN1A
IN1B
IN2
PA
LDO2
PA
A
PA STEP-DOWN CONVERTER
LINE-TRANSIENT RESPONSE
PA STEP-DOWN CONVERTER
SOFT-START WAVEFORMS
MAX8836Z toc09
MAX8836Z toc08
4.2V
3.6V
2V/div
V
PA_EN
V
IN1_
2V/div
V
PA
200mV/div
AC-COUPLED
V
PA
500mA/div
200mA/div
V
LX
I
LX
R
= 7.5Ω
PA
200µs/div
20µs/div
PA STEP-DOWN CONVERTER
SHUTDOWN RESPONSE
PA STEP-DOWN CONVERTER
LOAD-TRANSIENT RESPONSE
MAX8836Z toc11
MAX8836Z toc10
V
PA_EN
2V/div
2V/div
500mA/div
I
PA
PA
V
200mV/div
PA
V
AC-COUPLED
200mV/div
AC-COUPLED
I
V
LX
IN
500mA/div
R = 7.5Ω
L
10µs/div
10µs/div
LDO2 DROPOUT VOLTAGE
vs. LOAD CURRENT
LDO2 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
150
120
90
60
30
0
140
120
100
80
60
40
V
= V
= 0V,
IN1B
IN1A
EN2 = IN2,
PA_EN = PGND,
= 0A
20
I
LDO2
0
0
50
100
150
200
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY VOLTAGE (V)
LOAD CURRENT (mA)
_______________________________________________________________________________________
5
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Typical Operating Characteristics (continued)
(V
noted.)
= V
= V
= 3.6V, V = 3.4V, V
= 2.85V, R = 7.5Ω, circuit of MAX8805WEVKIT, T = +25°C, unless otherwise
IN1A
IN1B
IN2
PA
LDO2
PA
A
LDO POWER-SUPPLY
REJECTION RATIO vs. FREQUENCY
LDO OUTPUT NOISE SPECTRAL DENSITY
vs. FREQUENCY
LDO2 OUTPUT NOISE WAVEFORM
MAX8836Z toc16
80
70
60
50
40
30
20
10
10,000
1,000
100
MAX836Z
50mV/div
I
= 30mA
0.1
LDO
10
0.01
1
10
100
1000
400µs/div
0.01
0.1
1
10
100
1000
FREQUENCY (kHz)
FREQUENCY (kHz)
LDO2 LOAD-TRANSIENT RESPONSE
NEAR DROPOUT
LDO2 LINE-TRANSIENT RESPONSE
MAX8836Z toc17
MAX8836Z toc18
4.0V
3.6V
V
IN2
50mV/div
AC-COUPLED
V
LDO2
10mV/div
AC-COUPLED
V
LDO2
100mA/div
I
LDO2
I
= 80mA
LDO2
V
= V
+ 200mV
LDO2
IN2
200µs/div
20µs/div
LDO2 SHUTDOWN RESPONSE
MAX8836Z toc19
2V/div
V
EN2
2V/div
V
LDO2
1ms/div
6
_______________________________________________________________________________________
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
MAX836Z
Pin Description
PIN
NAME
FUNCTION
Reference Noise Bypass. Bypass REFBP to AGND with a 0.22µF ceramic capacitor to reduce noise on the
LDO outputs. REFBP is internally pulled down through a 1kΩ resistor during shutdown.
A1
REFBP
Low-Noise Analog Ground. Connect AGND to PGND using a common ground plane. Refer to the
MAX8805W Evaluation Kit for more information.
A2
A3
A4
AGND
N.I.C.
PGND
Not Internally Connected. Connect to AGND for improved thermal performance.
Power Ground for PA Step-Down Converter. Connect AGND to PGND using a common ground plane. Refer
to the MAX8805W Evaluation Kit for more information.
200mA LDO Regulator 2 Output. Bypass LDO2 with a 1µF ceramic capacitor as close as possible to LDO2
and AGND. LDO2 is internally pulled down through a 1kΩ resistor when this regulator is disabled.
PA Step-Down Converter Enable. Active-high enable input. Connect to IN1A/IN1B or logic-high for normal
operation. Pulled down to ground through an internal 800kΩ resistor.
B1
B2
LDO2
PA_EN
LDO2 Enable. Active-high enable input. Connect to IN2 or logic-high for normal operation. Pulled down to
ground through an internal 800kΩ resistor.
B3
B4
EN2
LX
Inductor Connection. Connect an inductor from LX to the output of the PA step-down converter.
Supply Voltage Input for LDO2 and Internal Reference. Connect IN2 to a battery or supply voltage from
2.7V to 5.5V. Bypass IN2 with a 2.2µF ceramic capacitor as close as possible to IN2 and AGND. Connect
IN2 to the same source as IN1A and IN1B.
C1
C2
IN2
HP
PA Output Voltage Select. Pulled down to ground through an internal 800kΩ resistor.
Supply Voltage Input for PA Step-Down Converter. Connect IN1_ to a battery or supply voltage from 2.7V to
5.5V. Bypass the connection of IN1_ with a 4.7µF ceramic capacitor as close as possible to IN1_ and
PGND. IN1A and IN1B are internally connected together. Connect IN1_ to the same source as IN2.
IN1B,
IN1A
C3, C4
D1
D2
N.C.
T.P.
Internally Connected to IN2. Do not connect to this pin.
Test Point. This pin is used internally for factory test. This pin must be either externally connected to AGND
or unconnected. This pin has an internal 120kΩ pulldown to AGND.
PA Connection for Bypass Mode. Internally connected to IN1_ using the internal bypass MOSFET during
D3, D4
PAB, PAA bypass mode. PA_ is connected to the internal feedback network. Bypass PA_ with a 4.7µF ceramic
capacitor as close as possible to PA_ and PGND.
_______________________________________________________________________________________
7
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
IN1A
IN1B
BYPASS FET
R4
R5
PAA
PAB
C1
R3
CURRENT-LIMIT CONTROL
REF
MAX836Z
PWM ERROR
COMPARATOR
HP
R7
R6
LX
PWM LOGIC
C2
PGND
STEP-DOWN CURRENT LIMIT
R2
R1
IN2
REFBP
AGND
1.25V
REFERENCE
BANDGAP
LDO2 CURRENT LIMIT
BANDGAP
LDO2
ERROR AMP
R12
EN2
CONTROL
LOGIC
PA_EN
R11
R10
Figure 1. Block Diagram
8
_______________________________________________________________________________________
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
MAX836Z
Automatic Bypass Mode
Detailed Description
Forced bypass mode is automatically invoked when the
The MAX8836Z is designed to provide a fixed output
DC-DC converter operates at more than 99% duty cycle
(typ). See Figure 2. Note that IN2 is used instead of IN1
to prevent switching noise from causing false engage-
ment of automatic bypass mode. For this reason, IN2
must be connected to the same source as IN1.
voltage of 3.4V with ultra-low dropout. The device con-
tains a high-frequency, high-efficiency step-down con-
verter, and 200mA low-noise LDO. The step-down
converter delivers over 1.2A. The hysteretic PWM con-
trol scheme provides extremely fast transient response.
A 60mΩ bypass FET connects directly to the battery
during high-power transmission.
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
Step-Down Converter Control Scheme
A hysteretic PWM control scheme ensures high effi-
ciency, fast switching, fast transient response, low-out-
put ripple, and physically tiny external components.
The control scheme is simple: when the output voltage
is below the regulation threshold, the error comparator
begins a switching cycle by turning on the high-side
switch. This high-side switch remains on until the mini-
mum on-time expires and the output voltage is within
regulation, or the inductor current is above the current-
limit threshold. Once off, the high-side switch remains
off until the minimum off-time expires and the output
voltage falls again below the regulation threshold.
During the off period, the low-side synchronous rectifier
turns on and remains on until the high-side switch turns
on again. The internal synchronous rectifier eliminates
the need for an external Schottky diode.
1.0
IN2
PAA/PAB
0.5
0
0
5
10 15 20 25 30 35 40 45 50
TIME (ms)
Figure 2. V
Mode
and V
with Automatic Entry/Exit into Bypass
IN2
PA_
Voltage-Positioning Load Regulation
The MAX8836Z step-down converter utilizes a unique
feedback network. By taking DC feedback from the LX
node through R1 in Figure 1, the usual phase lag due to
the output capacitor is removed, making the loop
exceedingly stable and allowing the use of very small
ceramic output capacitors. To improve the load regula-
tion, resistor R3 is included in the feedback. This config-
uration yields load regulation equal to half of the
inductor’s series resistance multiplied by the load cur-
rent. This voltage-positioning load regulation greatly
reduces overshoot during load transients or when
changing the output voltage from one level to another.
Shutdown Mode
Connect PA_EN to GND or logic-low to place the
MAX8836Z PA step-down converter in shutdown mode.
In shutdown, the control circuitry, internal switching
MOSFET, and synchronous rectifier turn off and LX
becomes high impedance. Connect PA_EN to IN1_ or
logic-high for normal operation.
Connect EN2 to GND or logic-low to place LDO2 in
shutdown mode. In shutdown, the output of the LDO is
pulled to ground through an internal 1kΩ resistor.
When the PA step-down and LDO are in shutdown, the
MAX8836Z enters a very low power state, where the
input current drops to 0.1µA (typ).
Step-Down Converter Bypass Mode
During high-power transmission, the bypass mode con-
nects IN1A and IN1B directly to PAA and PAB with the
internal 60mΩ (typ) bypass FET, while the step-down
converter is forced into 100% duty-cycle operation. The
low on-resistance in this mode provides low dropout,
long battery life, and high output current capability.
Step-Down Converter Soft-Start
The MAX8836Z PA step-down converter has internal
soft-start circuitry that limits inrush current at startup,
reducing transients on the input source. Soft-start
is particularly useful for supplies with high output
impedance such as Li+ and alkaline cells. See the PA
Step-Down Converter Soft-Start Waveforms in the
Typical Operating Characteristics.
_______________________________________________________________________________________
9
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Thermal Shutdown
Thermal shutdown limits total power dissipation in the
MAX8836Z. If the junction temperature exceeds
+160°C, thermal-shutdown circuitry turns off the IC,
allowing it to cool. The IC turns on and begins soft-start
after the junction temperature cools by 20°C. This
results in a pulsed output during continuous thermal-
overload conditions.
Output Capacitor Selection
For the PA step-down converter, the output capacitor
(C ) is required to keep the output voltage ripple small
PA
and ensure regulation loop stability. C must have low
PA
impedance at the switching frequency. Ceramic capaci-
tors with X5R or X7R dielectric are highly recommended
due to their small size, low ESR, and small temperature
coefficients. Due to the unique feedback network, the
output capacitance can be very low. A 4.7µF capacitor
is recommended for most applications. For optimum
load-transient performance and very low output ripple,
the output capacitor value can be increased.
Applications Information
MAX836Z
Output Voltages
The MAX8836Z provides a fixed output voltage of 3.4V
(HP = 0), or BYPASS mode if duty cycle is higher than
99% (typ).
For LDO2, the minimum output capacitance required is
dependent on the load currents. For loads less than
10mA, it is sufficient to use a 0.1µF capacitor for stable
operation over the full temperature range. With rated
maximum load currents, a minimum of 1µF is recom-
mended. Reduce output noise and improve load-tran-
sient response, stability, and power-supply rejection by
using larger output capacitors.
If HP = 1, the MAX8836Z provides a 3.1V fixed output
voltage.
The LDO2 output voltage is factory preset to 2.85V.
LDO Dropout Voltage
The regulator’s minimum input/output differential (or
dropout voltage) determines the lowest usable supply
voltage. In battery-powered systems, this determines
the useful end-of-life battery voltage. Because the
MAX8836Z LDO uses a p-channel MOSFET pass transis-
tor, the dropout voltage is a function of drain-to-source
Note that some ceramic dielectrics exhibit large capaci-
tance and ESR variation with temperature. With dielectrics
such as Z5U and Y5V, it is necessary to use 2.2µF or larg-
er to ensure stability at temperatures below -10°C. With
X7R or X5R dielectrics, 1µF is sufficient at all operating
temperatures. These regulators are optimized for ceramic
capacitors. Tantalum capacitors are not recommended.
on-resistance (R
) multiplied by the load current
DS(ON)
(see the Typical Operating Characteristics).
Input Capacitor Selection
Inductor Selection
The input capacitor (C ) of the PA converter reduces
IN1
The MAX8836Z operates with a switching frequency of
1.6MHz and utilizes a 2.2µH inductor. The switching
frequency of the MAX8836Z results in great efficiency
with a physically small inductor. See the Typical
Operating Characteristics for efficiency graphs.
the current peaks drawn from the battery or input
power source and reduces switching noise in the
MAX8836Z. The impedance of C
at the switching
IN1
frequency should be kept very low. Ceramic capacitors
with X5R or X7R dielectric are highly recommended
due to their small size, low ESR, and small temperature
coefficients. A 4.7µF capacitor is recommended for
most applications. For optimum noise immunity and low
input ripple, the input capacitor value can be
increased.
The inductor’s DC current rating only needs to match the
maximum load of the application because the
MAX8836Z features zero current overshoot during start-
up and load transients. For optimum transient response
and high efficiency, choose an inductor with DC series
resistance in the 50mΩ to 150mΩ range. See Table 1 for
suggested inductors and manufacturers.
10 ______________________________________________________________________________________
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
MAX836Z
Table 1. Suggested Inductors
INDUCTANCE
(µH)
ESR
(Ω)
CURRENT RATING
(mA)
DIMENSIONS
(mm)
MANUFACTURER
SERIES
1.0
1.5
2.2
0.07
0.10
0.13
1600
1400
1100
Coilcraft
LPO3310
3.3 x 3.3 x 1.0 = 11mm3
2.5 x 2.0 x 1.0 = 5mm3
1.0
1.5
2.2
0.05
0.07
0.08
1500
1500
1300
MIPF2520
FDK
1.3
2.0
0.09
0.11
1500
1200
MIPS2520
MIPF2016
2.5 x 2.0 x 1.0 = 5mm3
2.0 x 1.6 x 1.0 = 3.2mm3
3.2 x 2.5 x 1.7 = 14mm3
1.0
2.2
0.11
1100
1.0
2.2
0.06
0.10
1000
790
Murata
Sumida
LQH32C_53
1.2
1.5
2.2
0.08
0.09
0.12
590
520
440
CDRH2D09
CDRH2D11
3.0 x 3.0 x 1.0 = 9mm3
3.2 x 3.2 x 1.2 = 12mm3
1.5
2.2
3.3
0.05
0.08
0.10
680
580
450
Taiyo Yuden
2.2
4.7
0.09
0.13
510
340
CB2518T
D3010FB
D2812C
2.5 x 1.8 x 2.0 = 9mm3
3.0 x 3.0 x 1.0 = 9mm3
3.0 x 3.0 x 1.2 = 11mm3
1.0
0.20
1170
1.2
2.2
0.09
0.15
860
640
TOKO
1.5
2.2
0.13
0.17
1230
1080
D310F
D312C
3.6 x 3.6 x 1.0 = 13mm3
3.6 x 3.6 x 1.2 = 16mm3
1.5
2.2
0.10
0.12
1290
1140
For the LDO, use an input capacitance equal to the
value of the output capacitance of LDO2. Larger input
capacitor values and lower ESR provide better noise
rejection and line-transient response.
Thermal Considerations
In most applications, the MAX8836Z does not dissipate
much heat due to the high efficiency. However, in
applications where the MAX8836Z operates at high
ambient temperature with heavy loads, the heat dissi-
pated may exceed the maximum junction temperature
of the IC. If the junction temperature reaches approxi-
mately +160°C, all power switches are turned off and
LX and PA_ become high impedance, and LDO2 is
pulled down to ground through an internal 1kΩ pull-
down resistor.
Note that some ceramic dielectrics exhibit large capaci-
tance and ESR variation with temperature. With
dielectrics such as Z5U and Y5V, it may be necessary to
use two times the output capacitor value of LDO2 (or
larger) to ensure stability at temperatures below -10°C.
With X7R or X5R dielectrics, a capacitance equal to the
output capacitor value is sufficient at all operating tem-
peratures.
______________________________________________________________________________________ 11
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
The MAX8836Z maximum power dissipation depends
PCB Layout
High switching frequencies and relatively large peak cur-
rents make the PCB layout a very important part of
design. Good design minimizes excessive EMI on the
feedback paths and voltage gradients in the ground
plane, resulting in a stable and well-regulated output.
on the thermal resistance of the IC package and circuit
board, the temperature difference between the die
junction and ambient air, and the rate of airflow. The
power dissipated in the device is:
P
DISS
= P x (1/η - 1) + I
x (V
- V
)
LDO2
PA
PA
LDO2
IN2
Connect C
close to IN1A/IN1B and PGND. Connect
IN1
where η
is the efficiency of the PA step-down con-
PA
PA
the inductor and output capacitor as close as possible to
the IC and keep their traces short, direct, and wide. Keep
noisy traces, such as the LX node, as short as possible.
Figure 3 illustrates an example PCB layout and routing
scheme. Note that Figure 3 does not show the common
ground plane connection of AGND and PGND. Refer to
the MAX8805W Evaluation Kit for more information.
verter and P is the output power of the PA step-down
converter.
MAX836Z
The maximum allowed power dissipation is:
P
MAX
= (T
- T )/θ
JMAX A JA
where (T
- T ) is the temperature difference
A
JMAX
between the MAX8836Z die junction and the surround-
is the thermal resistance of the junction
ing air; θ
JA
through the PCB, copper traces, and other materials to
the surrounding air.
12 ______________________________________________________________________________________
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
MAX836Z
PGND
AGND
+
C
BYP
C
C
IN1
PA
C
LDO2
VIN
C
IN2
VPA
L
PA
5.5mm
Figure 3. Recommended PCB Layout
______________________________________________________________________________________ 13
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
MAX8836Z
IN1A
IN1B
Li+ BATTERY
MAX836Z
4.7µF
2.2µH*
LX
STEP-DOWN
PBA
4.7µF
PBB
BASEBAND
PROCESSOR
PGND
PA_EN
HP
GPIO
GPIO
IN
PA1
CONTROL
EN2
GPIO
EN/BIAS
REFBP
AGND
IN2
REF
0.22µF
0.1µF
1µF
LDO2
LDO2
*2.2µH FDK MIPF2520D2R2
Figure 4. Typical Application Circuit Using LDO for PA Enable/Bias
14 ______________________________________________________________________________________
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
MAX836Z
MAX8836Z
IN1A
Li+ BATTERY
4.7µF
IN1B
2.2µH*
LX
STEP-DOWN
PBA
4.7µF
PBB
BASEBAND
PROCESSOR
PGND
PA_EN
GPIO
GPIO
GPIO
IN
HP
PA
CONTROL
EN2
IN2
REFBP
AGND
REF
0.22µF
1µF
1µF
LDO2
IN
RF TRANSMITTER
LDO2
*2.2µH FDK MIPF2520D2R2
Figure 5. Typical Application Circuit Using LDO for RF Power
______________________________________________________________________________________ 15
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Pin Configuration
Chip Information
PROCESS: BiCMOS
TOP VIEW
(BUMPS ON BOTTOM)
+
REFBP
A1
AGND
A2
N.I.C.
A3
PGND
A4
LDO2
B1
PA_EN
B2
EN2
B3
LX
B4
MAX836Z
IN2
C1
HP
C2
IN1B
C3
IN1A
C4
N.C.
D1
T.P.
D2
PAB
D3
PAA
D4
WLP/UCSP
(2mm × 2mm)
16 ______________________________________________________________________________________
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
MAX836Z
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PACKAGE TYPE
16 UCSP
PACKAGE CODE
R162A2+1
DOCUMENT NO.
21-0226
16 WLP
W162B2+1
21-0200
______________________________________________________________________________________ 17
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
MAX836Z
18 ______________________________________________________________________________________
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
MAX836Z
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
1
3/08
9/08
Initial release
—
Added UCSP package option
1, 2, 16
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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