19-1400; Rev 0; 11/98
NUAL
KIT MA
ATION
ET
EVALU
TA SHE
WS DA
FOLLO
Low-Noise, 5.5V-Input,
PWM Step-Down Regulator
Features
o
+2.7V to +5.5V Input Range
o
Adjustable Output from 1.25V to V
IN
o
600mA Guaranteed Output Current
o
95% Efficiency
o
No Schottky Diode Required
o
85µA Quiescent Current
o
100% Duty Cycle in Dropout
o
750kHz Fixed-Frequency PWM Operation
o
Synchronizable Switching Frequency
o
Accurate Reference: 1.25V (±1.2%)
o
Small 10-Pin µMAX Package
General Description
The MAX1692 is a low-noise, pulse-width-modulated
(PWM), DC-DC step-down converter. It powers logic
and transmitters in small wireless systems such as cellu-
lar phones, communicating PDAs, and handy-terminals.
The device features an internal synchronous rectifier for
high efficiency; it requires no external Schottky diode.
Excellent noise characteristics and fixed-frequency
operation provide easy post-filtering. The MAX1692 is
ideally suited for Li-Ion battery applications. It is also
useful for +3V or +5V fixed input applications.
The device operates in one of four modes. Forced PWM
mode operates at a fixed frequency regardless of the
load. Synchronizable PWM mode allows an external
switching frequency to control and minimize harmonics.
Idle Mode™ (PWM/PFM) extends battery life by switch-
ing to a PFM pulse-skipping mode during light loads.
Shutdown mode places the device in standby, reduc-
ing quiescent supply current to under 0.1µA.
The MAX1692 can deliver over 600mA. The output volt-
age can be adjusted from 1.25V to V
IN
with the input
range of +2.7V to +5.5V. Other features of the
MAX1692 include high efficiency, low dropout voltage,
and a 1.2%-accurate 1.25V reference. It is available in
a space-saving 10-pin µMAX package with a height of
only 1.11mm.
MAX1692
Ordering Information
PART
MAX1692EUB
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
10 µMAX
Pin Configuration
TOP VIEW
IN
1
BP
GND
REF
FB
2
3
4
5
10
PGND
9
LX
SHDN
SYNC/PWM
LIM
Applications
Cellular Phones
Cordless Phones
CPU I/O Supplies
Notebook Chipset Supplies
MAX1692
8
7
6
PDAs and Handy-Terminals Battery-Operated Devices
(1 Li-Ion or 3 NiMH/NiCd)
µMAX
Typical Operating Circuit
L
V
IN
= 2.7V TO 5.5V
C1
IN
SHDN
LIM
R1
LX
C2
V
OUT
= 1.25V TO V
IN
MAX1692
BP
C3
AGND
REF
FB
R2
SYNC/PWM
PGND
C4
Idle Mode is a trademark of Maxim Integrated Products.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
Low-Noise, 5.5V-Input,
PWM Step-Down Regulator
MAX1692
ABSOLUTE MAXIMUM RATINGS
IN, BP,
SHDN,
SYNC/PWM, LIM to GND ................ -0.3V to +6V
BP to IN .................................................................-0.3V to +0.3V
PGND to GND ...................................................... -0.3V to +0.3V
LX to PGND................................................. -0.3V to (V
IN
+ 0.3V)
FB, REF to GND ......................................... -0.3V to (V
BP
+ 0.3V)
Reference Current ............................................................. ±1mA
LX Peak Current (internally limited)...................................... 1.6A
Continuous Power Dissipation (T
A
= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C) ............444mW
Operating Temperature Range .......................... -40°C to +85°C
Maximum Junction Temperature .................................... +150°C
Storage Temperature Range ............................ -65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+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.
ELECTRICAL CHARACTERISTICS
(V
IN
= +3.6V, SYNC/PWM = GND, V
LIM
= 3.6V,
SHDN
= IN, circuit of Figure 2;
T
A
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
Input Voltage Range
SYMBOL
V
IN
FB = OUT, V
IN
= V
LIM
= 2.7V to 5.5V,
I
OUT
= 0
Output Voltage
V
OUT
FB = OUT, V
IN
= 2.7V to 5.5V,
I
OUT
= 0 to 600mA, LIM = IN or
I
OUT
= 0 to 250mA, LIM = GND
(Note 1)
V
FB
FB = OUT, V
IN
= V
LIM
= 5.5V, I
OUT
= 0
(duty cycle = 23%) (Note 2)
Duty cycle = 100% to 23%
I
OUT
= 0 to 600mA, LIM = IN or
I
OUT
= 0 to 250mA, LIM = GND
I
FB
P
RDS(ON)
N
RDS(ON)
V
FB
= 1.4V
I
LX
= 180mA
I
LX
= 180mA
V
IN
= 3.6V
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 2.7V
0.35
0.75
-450
0
80
SYNC/PWM = GND, V
FB
= 1.4V,
LX unconnected
SHDN
= LX = GND, includes LX leakage
current
V
IN
= 5.5V, V
LX
= 0 or 5.5V
f
OSC
duty
MAX
duty
MIN
V
REF
I
REF
= 0
1.235
1.250
-20
650
500
100
22
1.265
-50
CONDITIONS
MIN
2.7
1.223
1.249
TYP
MAX
5.5
1.275
V
1.190
V
REF
1.223
1.249
+1
-1.3
0.01
0.3
0.4
0.4
0.5
0.6
1.2
-850
50
120
85
0.1
0.1
750
50
0.65
0.8
0.85
1.55
-1600
100
160
140
10
20
830
1000
1.232
1.275
V
IN
1.275
V
V
%
%
nA
Ω
Ω
A
mA
mA
µA
µA
µA
kHz
kHz
%
%
V
UNITS
V
Output Adjustment Range
Feedback Voltage
Line Regulation
Load Regulation
FB Input Current
P-Channel On-Resistance
N-Channel On-Resistance
P-Channel Current-Limit
Threshold
N-Channel Current-Limit
Threshold
Pulse-Skipping Current-Limit
Threshold
Quiescent Current
Shutdown Supply Current
LX Leakage Current
Oscillator Frequency
SYNC Capture Range
Maximum Duty Cycle
Minimum Duty Cycle
Reference Output Voltage
2
LIM = GND
LIM = IN
V
FB
= 1.4V
SYNC/PWM = IN, FB = REF
_______________________________________________________________________________________
Low-Noise, 5.5V-Input,
PWM Step-Down Regulator
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +3.6V, SYNC/PWM = GND, V
LIM
= 3.6V,
SHDN
= IN, circuit of Figure 2;
T
A
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
Reference Load Regulation
Undervoltage Lockout Threshold
Logic Input High
Logic Input Low
Logic Input Current
SYNC/PWM Minimum Pulse Width
UVLO
V
IH
V
IL
SYMBOL
0
≤
I
REF
≤
50µA
V
IN
rising, typical hysteresis is 85mV
SHDN,
SYNC/PWM, LIM
SHDN,
SYNC/PWM, LIM
SHDN,
SYNC/PWM, LIM
High or low
-1
500
0.1
2.3
2
0.4
1
CONDITIONS
MIN
TYP
3
2.4
MAX
15
2.5
UNITS
mV
V
V
V
µA
ns
MAX1692
ELECTRICAL CHARACTERISTICS
(V
IN
= +3.6V, SYNC/PWM = GND, V
LIM
= 3.6V,
SHDN
= IN, circuit of Figure 2,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 3)
PARAMETER
Input Voltage Range
SYMBOL
V
IN
FB = OUT, V
IN
= V
LIM
= 2.7V to 5.5V,
I
OUT
= 0
Output Voltage
V
OUT
FB = OUT, V
IN
= 2.7V to 5.5V,
I
OUT
= 0 to 600mA, LIM = IN or
I
OUT
= 0 to 250mA, LIM = GND
(Note 1)
V
FB
I
FB
FB = OUT, V
IN
= V
LIM
= 5.5V, I
OUT
= 0
(duty cycle = 23%) (Note 2)
V
FB
=1.4V
LIM = GND
LIM = IN
SYNC/PWM = IN, FB = REF
SYNC/PWM = GND, LX = unconnected,
V
FB
= 1.4V
SHDN
= LX = GND, includes LX leakage current
f
OSC
V
REF
UVLO
V
IH
V
IL
I
REF
= 0
V
IN
rising, typical hysteresis is 85mV
SHDN,
SYNC/PWM, LIM
SHDN,
SYNC/PWM, LIM
SHDN,
SYNC/PWM, LIM
-1
630
1.230
2.3
2
0.4
1
CONDITIONS
MIN
2.7
1.213
MAX
5.5
1.285
V
1.185
REF
1.213
-50
0.3
0.7
-15
1.285
V
IN
1.285
50
0.9
1.6
110
140
10
840
1.268
2.5
V
V
nA
A
mA
µA
µA
kHz
V
V
V
V
µA
UNITS
V
Output Adjustment Range
Feedback Voltage
FB Input Current
P-Channel Current-Limit
Threshold
N-Channel Current-Limit
Threshold
Quiescent Current
Shutdown Supply Current
Oscillator Frequency
Reference Output Voltage
Undervoltage Lockout
Threshold
Logic Input High
Logic Input Low
Logic Input Current
Note 1:
Guaranteed by minimum and maximum duty-factor tests.
Note 2:
The following equation can be used to calculate FB accuracy for output voltages other than 1.232V:
(see Feedback Voltage vs. Load Current)
V
FB
= V
FB (NOMINAL)
- (Line Reg) (V
OUT
/ V
IN
- 0.23) / 0.77 - (Load Reg)(I
OUT
+ 0.5
·
I
RIPPLE
) / I
MAX
where: Line Reg = the line regulation
Load Reg = the load regulation
I
RIPPLE
= (1- V
OUT
/ V
IN
)
·
V
OUT
/ (f
OSC
·
L) where L is the inductor value
I
MAX
= 250mA (LIM = GND) or 600mA (LIM = IN)
Note 3:
Specifications to -40°C are guaranteed by design, not production tested.
_______________________________________________________________________________________
3
Low-Noise, 5.5V-Input,
PWM Step-Down Regulator
MAX1692
Typical Operating Characteristics
(SYNC/PWM = GND, circuit of Figure 2, L = Sumida CD43-100, T
A
= +25°C, unless otherwise noted.)
DROPOUT VOLTAGE vs.
LOAD CURRENT
MAX1692-01
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 3.3V)
MAX1692-02
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 2.5V)
95
90
EFFICIENCY (%)
MAX1692-03
600
500
DROPOUT VOLTAGE (mV)
400
300
200
100
0
0
150
300
450
600
750
V
OUT
= 2.5V
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
LIM = IN
R1 = 505kΩ
R2 = 301kΩ
1
10
100
V
IN
= 5.0V
V
IN
= 3.6V
100
85
80
75
70
65
60
55
50
1
10
V
IN
= 5.0V
V
IN
= 3.6V
V
IN
= 2.7V
V
OUT
= 3.3V
LIM = IN
R1 = 309kΩ
R2 = 301kΩ
100
1000
900
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 1.8V)
MAX1692-04
FEEDBACK VOLTAGE
vs. LOAD CURRENT
MAX1692-05
BATTERY INPUT CURRENT vs.
INPUT VOLTAGE
95
BATTERY INPUT CURRENT (µA)
90
85
80
75
70
65
60
T
A
= -40°C
V
OUT
= 1.8V
SYNC/PWM = GND
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
T
A
= +25°C
MAX1692-06
100
95
90
EFFICIENCY (%)
V
IN
= 3.6V
V
IN
= 5.0V
V
IN
= 2.7V
1.25
1.245
1.24
FB VOLTAGE (V)
1.235
1.23
1.225
1.22
1.215
LIM = GND
LIM = IN
V
IN
= 5.0V
R1 = 309kΩ
R2 = 301kΩ
SYNC/PWM = GND
100
T
A
= +85°C
85
80
75
70
65
60
55
50
1
10
100
1000
LOAD CURRENT (mA)
LIM = IN
R1 = 138kΩ
R2 = 301kΩ
1.21
1.205
1.2
0 100 200 300 400 500 600 700 800 900 1000
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
BATTERY INPUT CURRENT vs.
INPUT VOLTAGE
MAX1692-07
BATTERY INPUT CURRENT vs. INPUT
VOLTAGE AND TEMPERATURE
MAX1692-09
OUTPUT VOLTAGE vs.
LOAD CURRENT
V
IN
= 2.7V
V
OUT
= 1.8V
R1 = 138kΩ
R2 = 301kΩ
MAX1692-10
5.0
4.5
BATTERY INPUT CURRENT (mA)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
2.7
3.1
3.5
3.9
4.3
4.7
5.1
SYNC/PWM = IN
V
OUT
= 1.8V
V
OUT
= 2.5V
V
OUT
= 3.3V
2.5
BATTERY INPUT CURRENT (mA)
1.84
2.0
OUTPUT VOLTAGE (V)
T
A
= +85°C
1.82
1.80
T
A
= +25°C
1.5
T
A
= -40°C
V
OUT
= 1.8V
SYNC/PWM = IN
1.0
1.78
1.76
1.74
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
0
100 200 300 400 500 600 700 800 900
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
5.5
INPUT VOLTAGE (V)
4
_______________________________________________________________________________________
Low-Noise, 5.5V-Input,
PWM Step-Down Regulator
Typical Operating Characteristics (continued)
(SYNC/PWM = GND, T
A
= +25°C, unless otherwise noted.)
MAX1692
OSCILLATOR FREQUENCY vs.
SUPPLY VOLTAGE
MAX1692-11
MAXIMUM OUTPUT CURRENT vs.
INPUT VOLTAGE
MAX1692-12
START-UP FROM SHUTDOWN
V
SHDN
2V/div
MAX1692-14
800
T
A
= +85°C
OSCILLATOR FREQUENCY (kHz)
750
T
A
= +25°C
700
T
A
= -40°C
650
I
OUT
= 200mA
600
2.7
3.1
3.5
3.9
4.3
4.7
5.1
1.4
MAXIMUM OUTPUT CURRENT (A)
LIM = IN
1.1
V
OUT
1V/div
0.8
LIM = GND
0.5
V
OUT
= 1.8V
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
2ms/div
INPUT VOLTAGE (V)
I
IN
0.5A/div
5.5
SUPPLY VOLTAGE (V)
HEAVY LOAD SWITCHING WAVEFORMS
MAX1692-15
LOAD-TRANSIENT RESPONSE
MAX1692-17
LINE-TRANSIENT RESPONSE
V
IN
AC-
COUPLED
2V/div
V
OUT
AC-
COUPLED
50mV/div
MAX1692-18
V
LX
5V/div
I
LX
0.5A/div
V
LX
5V/div
I
OUT
2.5A/div
V
OUT
AC-
COUPLED
100mV/div
V
OUT
AC-COUPLED
100mV/div
2ms/div
V
IN
= 5V, V
OUT
= 3.3V, I
OUT
= 700mA
500µs/div
I
LOAD
= 30mA to 700mA
2ms/div
V
IN
= 3V to 5V, I
OUT
= 300mA
RECOVERY FROM 100% DUTY CYCLE
MAX1692-19
SWITCHING HARMONICS AND NOISE
MAX1692-22
V
IN
2V/div
V
LX
5V/div
V
OUT
AC-
COUPLED
500mV/div
1mV/div
2ms/div
V
IN
= 3.3V to 4.5V , V
OUT
= 3.3V, I
OUT
= 500mA
100kHz
I
OUT
= 500mA
1MHz
1ms/div
10MHz
_______________________________________________________________________________________
5
