19-2641; Rev 0; 10/02
IT
TION K
VALUA
E
BLE
AVAILA
PWM Buck Converters with Bypass FET
for N-CDMA/W-CDMA Handsets
General Description
Features
o
Integrated Bypass PFET
o
150mV Dropout at 600mA Load (Regardless of
External Inductor)
o
Dynamically Adjustable Output from 0.4V to
V
BATT
o
Externally Fixed Output from 1.25V to 2.5V with
Digitally Controlled High-Power Bypass Mode
(MAX8504)
o
1MHz Fixed-Frequency PWM Switching
o
600mA Guaranteed Output Current
o
10% to 100% Duty-Cycle Operation
o
Low Quiescent Current
280µA (typ) in Normal Mode
3.3mA (typ) in PWM Mode
0.1µA (typ) in Shutdown Mode
o
12-Pin Thin QFN (4mm x 4mm, 0.8mm max Height)
MAX8500–MAX8504
The MAX8500–MAX8504 PWM DC-to-DC buck converters
are optimized with integrated bypass FET (0.25Ω typ)
to provide power to the PA in N-CDMA and W-CDMA
cell phones. The devices have a low on-resistance FET
to bypass the external inductor for low dropout of only
150mV at 600mA load, regardless of inductor series
resistance. The supply voltage range is from 2.6V to
5.5V and the guaranteed converter output current is
600mA. The 1MHz PWM switching frequency allows for
small external components.
The MAX8500–MAX8503 are dynamically controlled to
provide varying output voltages from 0.4V to V
BATT
.
The LDO regulation point is slightly lower than the PWM
converter such that the transition into and out of dropout
is smooth, regardless of the inductor resistance. The
MAX8504 is programmed for fixed 1.25V to 2.5V output
with external resistors. It features a high-power bypass
mode that connects the output directly to the battery. All
devices are designed to achieve an output settling time
of less than 30µs for a full-scale change in output volt-
age and load current.
The MAX8500–MAX8504 are available in a 12-lead
4mm x 4mm thin QFN package (0.8mm max height).
Ordering Information
PART
MAX8500ETC
MAX8501ETC*
MAX8502ETC*
MAX8503ETC
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
12 Thin QFN
12 Thin QFN
12 Thin QFN
12 Thin QFN
12 Thin QFN
TOP
MARK
AABQ
—
—
AABU
AABS
Applications
N-CDMA/W-CDMA Cellular Phones
Wireless PDAs and Modems
Typical Operating Circuit
INPUT 2.6V TO 5.5V
10µF
BATT
SKIP
SHDN
REF
1MHz
OSC
PWM
LDO
REFIN
DAC
LX
OUT
4.7µH
OUTPUT 0.4V TO V
BATT
4.7µF
MAX8504ETC
*Future
product—contact factory for availability.
Pin Configuration
SHDN
12
SKIP
11
OUT
10
GND
REF
g
m
1
2
3
9
BATT
BATTP
LX
MAX8500–
MAX8504
8
7
REFIN
(FB)
COMP
PGND
R
C
8.2kΩ
C
C
1000pF
MAX8500-
MAX8503
GND
4
COMP
5
BATT
(HP)
6
PGND
Thin QFN 4mm x 4mm
( ) MAX8504 ONLY
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
PWM Buck Converters with Bypass FET
for N-CDMA/W-CDMA Handsets
MAX8500–MAX8504
ABSOLUTE MAXIMUM RATINGS
BATTP, BATT, OUT,
SHDN, SKIP,
HP,
REFIN, FB to GND ....................................................-0.3V to +6V
PGND to GND .......................................................-0.3V to +0.3V
REF, COMP to GND ................................-0.3V to (V
BATT
+ 0.3V)
LX Current (Note 1) .............................................................2.25A
Output Short-Circuit Duration ........................................Indefinite
Continuous Power Dissipation (T
A
= +70°C)
12-Lead Thin QFN (derate 16.9mW/°C above +70°C) .1349mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
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.
Note 1:
LX has internal clamp diodes to PGND and BATTP. Applications that forward bias these diodes should take care not to
exceed the IC’s package power dissipation limits.
ELECTRICAL CHARACTERISTICS
(V
BATT
= V
BATTP
= 3.6V,
SHDN
=
SKIP
= BATT, V
REFIN
= 1.932V (MAX8500, MAX8502), V
REFIN
= 1.70V (MAX8501, MAX8503), C
REF
= 0.22µF, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
Input BATT Voltage
Undervoltage Lockout Threshold
Quiescent Current
SYMBOL
V
BATT
V
UVLO
I
Q
SKIP
= GND
SKIP
= BATT, no switching
SKIP
= BATT, switching
Quiescent Current in Dropout
Shutdown Supply Current
OUT Voltage Accuracy
(MAX8500, MAX8502)
OUT Voltage Accuracy
(MAX8501, MAX8503)
OUT Voltage-Load Regulation
OUT Voltage-Line Regulation
OUT Input Resistance
REFIN Input Current
REFIN to OUT Gain
(MAX8500, MAX8502)
REFIN to OUT Gain
(MAX8501, MAX8503)
Reference Voltage
Reference Load Regulation
Reference UVLO
FB Voltage Accuracy (MAX8504)
FB Input Current (MAX8504)
P-Channel On-Resistance
V
FB
I
FB
P
RDS
V
FB
= 1.3V
I
LX
= 180mA, V
BATT
= 3.6V
I
LX
= 180mA, V
BATT
= 2.6V
I
REF
A
V
A
V
V
REF
10µA < I
REF
< 100 µA
0.86
1.225
0.96
1.250
10
0.35
0.45
PWM buck
LDO linear regulator
PWM buck
LDO linear regulator
1.225
MAX8500, MAX8503
100
-1
I
SHDN
V
OUT
V
OUT
V
REFIN
= 2.2V (MAX8500, MAX8503),
HP = BATT (MAX8504)
SHDN
= GND, V
BATT
= V
BATTP
= 5.5V
V
REFIN
= 1.932V, load = 0 to 600mA
V
REFIN
= 0.227V
V
REFIN
= 1.700V, load = 0 to 600mA
V
REFIN
= 0.200V
3.33
0.35
3.33
0.35
CONDITIONS
V
BATT
rising, 1% hysteresis
MIN
2.6
2.15
TYP
2.35
280
450
3300
400
0.1
3.40
0.40
3.40
0.40
-0.05
0.007
245
0.1
1.76
1.68
2
1.909
1.25
1.275
6.25
1.10
1.275
150
0.70
+1
700
5
3.47
0.45
3.47
0.45
µA
µA
V
V
%/A
%/V
kΩ
µA
V/V
V/V
V
mV
V
V
nA
Ω
MAX
5.5
2.50
450
2200
µA
UNITS
V
V
2
_______________________________________________________________________________________
PWM Buck Converters with Bypass FET
for N-CDMA/W-CDMA Handsets
ELECTRICAL CHARACTERISTICS (continued)
(V
BATT
= V
BATTP
= 3.6V,
SHDN
=
SKIP
= BATT, V
REFIN
= 1.932V (MAX8500, MAX8502), V
REFIN
= 1.70V (MAX8501, MAX8503), C
REF
= 0.22µF, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
N-Channel On-Resistance
LDO/Bypass P-Channel
On-Resistance
P-Channel Current-Limit
Threshold
N-Channel Current-Limit
Threshold
P-Channel Pulse-Skipping
Current Threshold
LDO/Bypass P-Channel
Current-Limit Threshold
LX RMS Current
LX Leakage Current
Maximum Duty Cycle
Minimum Duty Cycle
COMP Clamp Low Voltage
COMP Clamp High Voltage
MAX8500, MAX8501
Transconductance
Current-Sense Transresistance
Internal Oscillator Frequency
LOGIC INPUTS (SHDN, HP,
SKIP)
Logic Input High
Logic Input Low
Logic Input Current
THERMAL SHUTDOWN
Thermal-Shutdown Temperature
Thermal-Shutdown Hysteresis
160
15
°C
°C
V
IH
V
IL
0.1
1.6
0.4
1.0
V
V
µA
g
m
R
CS
f
OSC
0.8
MAX8502, MAX8503
MAX8504
SKIP
= GND
SKIP
= BATT
0.7
2.0
85
75
150
10
1.0
2.3
142
125
250
0.38
1.0
1.2
(Note 3)
V
BATT
= V
BATTP
= 5.5V, V
LX
= 0 to 5.5V
-20
100
0
13
1.1
2.4
200
175
350
V/A
MHz
µS
+0.1
I
LIMP
I
LIMN
I
SKIP
SKIP
= BATT
SKIP
= GND
SKIP
= GND
SYMBOL
N
RDS
CONDITIONS
I
LX
= 180mA, V
BATT
= 3.6V
I
LX
= 180mA, V
BATT
= 2.6V
I
OUT
= 180mA, V
BATT
= 3.6V
I
OUT
= 180mA, V
BATT
= 2.6V
1.30
-0.80
30
118
0.70
MIN
TYP
0.26
0.33
0.25
0.3
1.45
-0.60
47
148
1.00
1.60
-0.40
65
178
1.55
1.5
+20
0.60
MAX
0.60
UNITS
Ω
Ω
A
A
mA
mA
A
A
µA
%
%
V
V
MAX8500–MAX8504
Note 2:
Specifications to -40°C are guaranteed by design and not subject to production test.
Note 3:
Guaranteed by design, not production tested.
_______________________________________________________________________________________
3
PWM Buck Converters with Bypass FET
for N-CDMA/W-CDMA Handsets
MAX8500–MAX8504
Typical Operating Characteristics
(V
BATT
= 3.6V, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT VOLTAGE
IN NORMAL MODE
MAX8500 toc01
EFFICIENCY vs. OUTPUT VOLTAGE
IN PWM MODE
R
LOAD
= 10Ω
90
EFFICIENCY (%)
R
LOAD
= 5Ω
80
R
LOAD
= 15Ω
70
MAX8500 toc02
EFFICIENCY vs. INPUT VOLTAGE
MAX8500 toc03
100
R
LOAD
= 10Ω
90
EFFICIENCY (%)
R
LOAD
= 5Ω
80
R
LOAD
= 15Ω
100
100
90
EFFICIENCY (%)
V
OUT
= 1.5V
V
OUT
= 3.4V
80
70
70
V
OUT
= 0.4V
SKIP = GND
R
LOAD
= 10Ω
50
60
SKIP = GND
50
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
OUTPUT VOLTAGE (V)
60
SKIP = BATT
50
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
OUTPUT VOLTAGE (V)
60
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
EFFICIENCY vs. LOAD CURRENT
V
OUT
= 2.5V;
NORMAL MODE
MAX8500 toc04
MAX8500/MAX8503
DROPOUT VOLTAGE vs. LOAD CURRENT
MAX8500 toc05
MAX8504
DROPOUT VOLTAGE vs. LOAD CURRENT
MAX8500 toc06
100
300
250
DROPOUT VOLTAGE (mV)
200
150
100
50
0
V
OUT
= 2.5V
V
OUT
= 3.4V
0.25
90
EFFICIENCY (%)
0.20
DROPOUT VOLTAGE (V)
80
V
OUT
= 1.5V; PWM
70
V
OUT
= 1.5V;
NORMAL MODE
60
V
OUT
= 2.5V; PWM
50
1
10
100
1000
LOAD CURRENT (mA)
0.15
0.10
0.05
V
OUT
= 3.5V
HP = BATT
0
0 100 200 300 400 500 600 700 800 900 1000
LOAD CURRENT (mA)
0 100 200 300 400 500 600 700 800 900 1000
LOAD CURRENT (mA)
MAX8500/MAX8503
ENTERING REGULATOR DROPOUT REGION
MAX8500 toc07
MAX8500/MAX8503
ENTERING REGULATOR DROPOUT REGION
MAX8500 toc08
MAX8500/MAX8503
ENTERING REGULATOR DROPOUT REGION
MAX8500 toc09
3.55
3.50
OUTPUT VOLTAGE (V)
3.45
3.40
3.35
3.30
3.25
3.20
3.15
R
LOAD
= 10Ω
R
LOAD
= 7.6Ω
R
LOAD
= 5Ω
L = SUMIDA CDRH3D16-4R7M
R
LOAD
= 15Ω
V
BATT
3.55
3.50
OUTPUT VOLTAGE (V)
3.45
3.40
3.35
3.30
3.25
3.20
3.15
V
BATT
R
LOAD
= 15Ω
R
LOAD
= 10Ω
R
LOAD
= 7.6Ω
R
LOAD
= 5Ω
L = TOKO D312F-4R7M
3.50
3.45
OUTPUT VOLTAGE (V)
3.40
3.35
3.30
3.25
3.20
0
V
OUT
= 3.4V;
SKIP = BATT
300
600
900
1200
1500
3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2
V
BATT
(V)
3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2
V
BATT
(V)
LOAD CURRENT (mA)
4
_______________________________________________________________________________________
PWM Buck Converters with Bypass FET
for N-CDMA/W-CDMA Handsets
MAX8500–MAX8504
Typical Operating Characteristics (continued)
(V
BATT
= 3.6V, T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE IN PWM MODE
MAX8500 toc10
SUPPLY CURRENT
vs. SUPPLY VOLTAGE IN NORMAL MODE
900
SUPPLY CURRENT (µA)
800
700
600
500
400
300
V
OUT
= 1.5V
V
OUT
= 3.4V
SKIP = GND
MAX8500 toc11
HEAVY-LOAD SWITCHING WAVEFORM
MAX8500 toc12
6
5
SUPPLY CURRENT (mA)
4
V
OUT
= 1.5V
3
2
1
0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
V
OUT
= 0.4V
SKIP = BATT
1000
V
LX
2V/div
200
5.5
2.0
2.5
3.0
3.5
SUPPLY VOLTAGE (V)
V
OUT
= 0.4V
4.0
4.5
5.0
5.5
V
IN
= 3.6V, V
OUT
= 3.3V
LOAD = 10Ω
400ns/div
V
OUT
AC-COUPLED
2mV/div
SUPPLY VOLTAGE (V)
MEDIUM-LOAD SWITCHING WAVEFORM
MAX8500 toc13
LIGHT-LOAD SWITCHING WAVEFORM
IN PWM MODE
MAX8500 toc14
LIGHT-LOAD SWITCHING WAVEFORM
IN SKIP MODE
MAX8500 toc15
V
LX
2V/div
V
LX
2V/div
V
LX
2V/div
V
IN
= 3.6V, V
OUT
= 0.4V
LOAD = 10Ω
V
OUT
AC-COUPLED
20mV/div
V
OUT
AC-COUPLED
5mV/div
V
IN
= 3.6V, V
OUT
= 1.5V
LOAD = 10Ω
400ns/div
V
IN
= 3.6V, V
OUT
= 0.4V
LOAD = 10Ω
400ns/div
V
OUT
AC-COUPLED
5mV/div
2µs/div
_______________________________________________________________________________________
5
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