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MAX8836ZEWEEE+T
1.2A PWM Step-Down Converter in 2mm x 2mm WLP/UCSP for PA Power
General DescriptionThe 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 60mΩtypical bypass FET for ultra
low-dropout operation. A 200mA low-noise, high-PSRR
low-dropout regulator (LDO) is also integrated.
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 (60mΩtyp) MOSFET. The
LDO in the MAX8836Z is designed for low-noise opera-
tion (35µVRMS typ). Both the PWM step-down and LDO
are individually enabled through separate logic-control
interfaces.
The MAX8836Z is available in 16-bump, 2mm x 2mm
WLP and UCSP™ packages (0.7mm max height).
ApplicationsWCDMA/NCDMA Cellular Handsets
Wireless PDAs
Smartphones
FeaturesPA Step-Down Converter
Selectable Output Voltage (3.1V or 3.4V)
25µs Settling Time for 3.1V to 3.4VOUTChange
60mΩPFET at 100% Duty-Cycle for Low
Dropout
Low Output Voltage Ripple
1.2A Output Drive Capability
±2% Output Voltage Accuracy
Tiny External ComponentsLow-Noise LDO
Low 35µVRMS(typ) Output Noise
High 65dB (typ) PSRR
Guaranteed 200mA Output Current Drive
Capability
ON/OFF ControlLow 0.1µA Shutdown Current2.7V to 5.5V Supply Voltage RangeThermal ShutdownTiny 2mm x 2mm x 0.7mm WLP and UCSP
Packages (4 x 4 Grid)
MAX8836Z
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Ordering Information2.2µH
INPUT
Li+ BATTERY
EN2
REFBP
SET OUTPUT
ENABLE LDO
LDO2PA_ENENABLE BUCK
4.7µF
4.7µF
MAX8836Z
0.22µF
200mA
1µF
OUTPUT
3.1V OR 3.4V
GND
Typical Operating Circuit19-4059; Rev 1; 9/08
+Denotes a lead-free/RoHS-compliant package.= Tape and reel.
UCSP is a trademark of Maxim Integrated Products, Inc.
Pin Configuration appears at end of data sheet.
PARTPIN-PACKAGETEMP RANGEMAX8836ZEWEEE+T16 WLP
(W162B2+1)-40°C to +85°C
MAX8836ZEREEE+T16 UCSP
(R162A2+1)-40°C to +85°C
MAX8836Z
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VIN1A= VIN1B= VIN2= VPA_EN = VEN2= 3.6V, VHP = 0V, TA= -40°C to +85°C. Typical values are at TA = +25°C, unless otherwise
noted.) (Note 1)
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.
IN1A, IN1B, IN2, EN2, REFBP to AGND................-0.3V to +6.0V
PAA, PAB, PA_EN, HP to AGND....-0.3V to (VIN1A/VIN1B+ 0.3V)
LDO2 to AGND..........................................-0.3V to (VIN2+ 0.3V)
IN2 to IN1B/IN1A...................................................-0.3V to +0.3V
PGND to AGND.....................................................-0.3V to +0.3V
LX Current......................................................................0.7ARMS
IN1A/IN1B and PAA/PAB Current.....................................2ARMS
PAA and PAB Short Circuit to GND or IN...................Continuous
Continuous Power Dissipation (TA= +70°C)
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
PARAMETERCONDITIONSMINTYPMAXUNITS
INPUT SUPPLYInput VoltageVIN1A, VIN1B, VIN22.75.5V
Input Undervoltage ThresholdVIN1A, VIN1B, VIN2 rising, 180mV typical hysteresis2.522.632.70V
HP, PA_EN, EN2 Pulldown
Resistor4008001600kΩ
TA = +25°C0.14Shutdown Supply CurrentVPA_EN = VEN2 = 0VTA = +85°C0.1µA
VPA_EN = 0V, ILDO2 = 0A100150
VEN2 = 0V, IPA = 0A, switching3500No-Load Supply Current
VEN2 = 0V, IPA = 0A, no switching180
THERMAL PROTECTIONThermal ShutdownTA rising, 20°C typical hysteresis+160°C
LOGIC CONTROLPA_EN, EN2, HP Logic-Input
High Voltage1.3V
PA_EN, EN2, HP Logic-Input Low
Voltage0.4V
TA = +25°C0.011Logic-Input Current
(PA_EN, EN2, HP)VIL = 0VTA = +85°C0.1µA
PA OUTPUT VOLTAGEHP = 03.3653.4343.503Output VoltageILX = 0A, VIN1A = VIN1B
= VIN2 = 3.9VHP = 13.0103.0653.190V
Output Voltage Load RegulationILX x
RL/2V
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.
MAX8836Z
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
PARAMETERCONDITIONSMINTYPMAXUNITSp-channel MOSFET switch, ILX = -40mA0.15On-Resistancen-channel MOSFET rectifier, ILX = 40mA0.15Ω
TA = +25°C0.15LX Leakage CurrentVIN1A = VIN1B = VIN2 = 5.5V,
VLX = 0VTA = +85°C1µA
p-Channel MOSFET Peak
Current LimitVLX = 0V1.31.51.8A
n-Channel MOSFET Valley
Current Limit1.11.31.6A
Minimum On- and Off-Times0.07µs
Power-Up DelayFrom PA_EN rising to LX rising80190µs
BYPASSTA = +25°C0.0600.1On-Resistancep-channel MOSFET bypass,
IPA = -90mATA = +85°C0.1Ω
Bypass Current LimitVPA = 0V0.81.41.8A
Total Bypass Current LimitVLX = VPA = 0V2.12.93.6A
Bypass ThresholdVIN2 rising, 150mV hysteresis0.985 x
VPAV/V
TA = +25°C0.015Bypass Off-Leakage CurrentVIN1A = VIN1B = VIN2 = 5.5V,
VPAA = VPAB = 0VTA = +85°C0.1µA
LDO2Output Voltage VLDO2VIN2 = 5.5V, ILDO2 = 1mA;
VIN2 = 3.4V, ILDO2 = 1mA2.7652.852.936V
Output Current200mA
Current LimitVLDO2 = 0V250550750mA
Dropout VoltageILDO2 = 100mA, TA = +25°C (VLDO2 ≥ 2.5V)70mV
Line RegulationVIN2 stepped from 3.5V to 5.5V, ILDO2 = 100mA2.4mV
Load RegulationILDO2 stepped from 50µA to 200mA25mV
Power-Supply Rejection
ΔVLDO2/ΔVIN210Hz to 10kHz, CLDO2 = 1µF, ILDO2 = 30mA65dB
Output Noise100Hz to 100kHz, CLDO2 = 1µF, ILDO2 = 30mA35µVRMS
0 < ILDO2 < 10mA100nFOutput Capacitor for Stable
Operation0 < ILDO2 < 200mA1µF
Shutdown Output ImpedanceVEN2 = 0V1kΩ
REFBPREFBP Output Voltage0 ≤ IREFBP ≤ 1µA1.2371.2501.263V
REFBP Supply RejectionVIN2 stepped from 2.55V to 5.5V0.25mV
ELECTRICAL CHARACTERISTICS (continued)(VIN1A= VIN1B= VIN2= VPA_EN = VEN2= 3.6V, VHP = 0V, TA= -40°C to +85°C. Typical values are at TA = +25°C, unless otherwise
noted.) (Note 1)
Note 1:All devices are 100% production tested at TA= +25°C. Limits over the operating temperature range are guaranteed by design.
MAX8836Z
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Typical Operating Characteristics(VIN1A= VIN1B= VIN2= 3.6V, VPA= 3.4V, VLDO2= 2.85V, RPA= 7.5Ω, circuit of MAX8805WEVKIT, TA= +25°C, unless otherwise
noted.)
BYPASS MODE DROPOUT VOLTAGE
vs. PA LOAD CURRENT
MAX8836Z toc01
PA LOAD CURRENT (A)
BYPASS MODE DROPOUT VOLTAGE (mV)
PA STEP-DOWN CONVERTER
EFFICIENCY vs. LOAD CURRENTMAX8836Z toc02
LOAD CURRENT (mA)
EFFICIENCY (%)
VIN1A = VIN1B = 3.6V
VIN1A = VIN1B = 3.9V
VIN1A = VIN1B = 4.2V
L = 2.2μH
FDK MIPF2520
PA STEP-DOWN CONVERTER
EFFICIENCY vs. LOAD CURRENTMAX8836Z toc03
LOAD CURRENT (mA)
EFFICIENCY (%)
VIN1A = VIN1B = 3.6V
VIN1A = VIN1B = 3.9V
VIN1A = VIN1B = 4.2V
L = 1μH
FDK MIPF2520
PA STEP-DOWN CONVERTER
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX8836Z toc04
LOAD CURRENT (mA)
PA OUTPUT VOLTAGE (V)
HP = PGND
HP = IN1A = IN1B
PA STEP-DOWN CONVERTER
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX8836Z toc05
INPUT VOLTAGE (V)
PA OUTPUT VOLTAGE (V)
HP = PGND
HP = IN1A = IN1B
1μs/div
PA STEP-DOWN CONVERTER LIGHT-LOAD
SWITCHING WAVEFORMSVPA
ILX200mA/div
50mV/div
AC-COUPLED
2V/div
MAX8836Z toc06
VLX
VPA = 3.4V, IPA = 50mA
1μs/div
PA STEP-DOWN CONVERTER
HEAVY-LOAD SWITCHINGVPA
ILX200mA/div
50mV/div
AC-COUPLED
2V/div
MAX8836Z toc07
VLX
VPA = 3.4V, IPA = 500mA
MAX8836Z
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Typical Operating Characteristics (continued)(VIN1A= VIN1B= VIN2= 3.6V, VPA= 3.4V, VLDO2= 2.85V, RPA= 7.5Ω, circuit of MAX8805WEVKIT, TA= +25°C, unless otherwise
noted.)
20μs/div
PA STEP-DOWN CONVERTER
SOFT-START WAVEFORMSVPA_EN
VPA
500mA/div
2V/div
2V/div
MAX8836Z toc08
ILX
200μs/div
PA STEP-DOWN CONVERTER
LINE-TRANSIENT RESPONSEVIN1_
VPA
200mA/div
4.2V
3.6V
MAX8836Z toc09
VLX
200mV/div
AC-COUPLED
RPA = 7.5Ω
10μs/div
PA STEP-DOWN CONVERTER
LOAD-TRANSIENT RESPONSEVPA
IPA
200mV/div
AC-COUPLED
500mA/div
MAX8836Z toc10
VIN
200mV/div
AC-COUPLED
10μs/div
PA STEP-DOWN CONVERTER
SHUTDOWN RESPONSEVPA
VPA_EN
500mA/div
2V/div
MAX8836Z toc11
ILX
2V/div
RL = 7.5Ω
LDO2 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX8836Z toc12
NO-LOAD SUPPLY CURRENT (
VIN1A = VIN1B = 0V,
EN2 = IN2,
PA_EN = PGND,
ILDO2 = 0A
LDO2 DROPOUT VOLTAGE
vs. LOAD CURRENT
MAX8836Z toc13
LDO2 DROPOUT VOLTAGE (mV)10050150200
MAX8836Z
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Typical Operating Characteristics (continued)(VIN1A= VIN1B= VIN2= 3.6V, VPA= 3.4V, VLDO2= 2.85V, RPA= 7.5Ω, circuit of MAX8805WEVKIT, TA= +25°C, unless otherwise
noted.)
LDO POWER-SUPPLY
REJECTION RATIO vs. FREQUENCYMAX8836Z toc14
FREQUENCY (kHz)
LDO PSRR (dB)
ILDO = 30mA
LDO OUTPUT NOISE SPECTRAL DENSITY
vs. FREQUENCYMAX8836Z toc15
FREQUENCY (kHz)
OUTPUT NOISE DENSITY NOISE (nV/
Hz)
1,000
10,000
0.011000400μs/div
LDO2 OUTPUT NOISE WAVEFORM50mV/div
MAX8836Z toc16
200μs/div
LDO2 LINE-TRANSIENT RESPONSEVLDO2
VIN24.0V
MAX8836Z toc17
3.6V
ILDO2 = 80mA
10mV/div
AC-COUPLED
20μs/div
LDO2 LOAD-TRANSIENT RESPONSE
NEAR DROPOUTILDO2
VLDO2
MAX8836Z toc18
VIN2 = VLDO2 + 200mV
100mA/div
50mV/div
AC-COUPLED
1ms/div
LDO2 SHUTDOWN RESPONSEVLDO2
VEN2
MAX8836Z toc19
2V/div
2V/div
MAX8836Z
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Pin Description
PINNAMEFUNCTIONREFBPReference 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.AGNDLow-Noise Analog Ground. Connect AGND to PGND using a common ground plane. Refer to the
MAX8805W Evaluation Kit for more information.N.I.C.Not Internally Connected. Connect to AGND for improved thermal performance.PGNDPower Ground for PA Step-Down Converter. Connect AGND to PGND using a common ground plane. Refer
to the MAX8805W Evaluation Kit for more information.LDO2200mA 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_ENPA 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.EN2LDO2 Enable. Active-high enable input. Connect to IN2 or logic-high for normal operation. Pulled down to
ground through an internal 800kΩ resistor.LXInductor Connection. Connect an inductor from LX to the output of the PA step-down converter.IN2
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.HPPA Output Voltage Select. Pulled down to ground through an internal 800kΩ resistor.
C3, C4IN1B,
IN1A
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.N.C.Internally Connected to IN2. Do not connect to this pin.T.P.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.
D3, D4PAB, PAA
PA Connection for Bypass Mode. Internally connected to IN1_ using the internal bypass MOSFET during
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.
MAX8836Z
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA PowerPWM LOGIC
STEP-DOWN CURRENT LIMIT
PWM ERROR
COMPARATOR
CURRENT-LIMIT CONTROL
PGND
PAA
BYPASS FETR1R4
IN2
ERROR AMP
LDO2 CURRENT LIMIT
BANDGAP
R11
R10
LDO2
R12
1.25V
REFERENCE
CONTROL
LOGIC
REFBP
AGND
BANDGAP
EN2
PA_EN
PAB
IN1B
IN1A
REF
Figure 1. Block Diagram
MAX8836Z
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Detailed DescriptionThe MAX8836Z is designed to provide a fixed output
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. Thestep-down
converter delivers over 1.2A. The hysteretic PWM con-
trol scheme provides extremely fast transient response.
A 60mΩbypass FET connects directly to the battery
during high-power transmission.
Step-Down Converter Control SchemeA 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.
Voltage-Positioning Load RegulationThe 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.
Step-Down Converter Bypass ModeDuring 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.
Automatic Bypass ModeForced bypass mode is automatically invoked when the
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.
Shutdown ModeConnect 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 1kΩresistor.
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 Soft-StartThe 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.
TIME (ms)
IN2 AND PAA/PAB VOLTAGE (V)
IN2
PAA/PAB
Figure 2. VIN2and VPA_with Automatic Entry/Exit into Bypass
Mode
MAX8836Z
1.2A PWM Step-Down Converter in
2mm x 2mm WLP/UCSP for PA Power
Thermal ShutdownThermal 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.
Applications Information
Output VoltagesThe MAX8836Z provides a fixed output voltage of 3.4V
(HP = 0), or BYPASS mode if duty cycle is higher than
99% (typ).
If HP = 1, the MAX8836Z provides a 3.1V fixed output
voltage.
The LDO2 output voltage is factory preset to 2.85V.
LDO Dropout VoltageThe 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
on-resistance (RDS(ON)) multiplied by the load current
(see the Typical Operating Characteristics).
Inductor SelectionThe 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 Characteristicsfor efficiency graphs.
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 50mΩto 150mΩrange. See Table 1 for
suggested inductors and manufacturers.
Output Capacitor SelectionFor the PA step-down converter, the output capacitor
(CPA) is required to keep the output voltage ripple small
and ensure regulation loop stability. CPAmust have low
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.
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.
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.
Input Capacitor SelectionThe input capacitor (CIN1) of the PA converter reduces
the current peaks drawn from the battery or input
power source and reduces switching noise in the
MAX8836Z. The impedance of CIN1at the switching
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.
