MAXIM MAX1626, MAX1627 Technical data
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19-1075; Rev 0; 6/96
EVALUATION KIT MANUAL
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High-Efficiency, Step-Down DC-DC Controllers
_______________General Description
The MAX1626/MAX1627 step-down DC-DC switching
controllers provide high efficiency over loads ranging
from 1mA to more than 2A. A unique current-limited,
pulse-frequency-modulated (PFM) control scheme
operates with up to a 100% duty cycle, resulting in very
low dropout voltages. This control scheme eliminates
minimum load requirements and reduces the supply
current under light loads to 90µA (versus 2mA to 10mA
for common pulse-width modulation controllers).
These step-down controllers drive an external P-channel MOSFET, allowing design flexibility for applications
to 12W or higher. Soft-start reduces current surges during start-up. A high switching frequency (up to 300kHz)
and operation in continuous-conduction mode allow the
use of tiny surface-mount inductors. Output capacitor
requirements are also reduced, minimizing PC board
area and system costs.
The output voltage is preset at 5V or 3.3V for the
MAX1626 and adjustable for the MAX1627. Input voltages can be up to 16.5V. The MAX1626/MAX1627 are
functional upgrades for the MAX1649/MAX1651.
________________________Applications
PCMCIA Power Supplies
Personal Digital Assistants
Hand-Held Computers
Portable Terminals
Low-Cost Notebook Computer Supplies
5V to 3.3V Green PC Applications
High-Efficiency Step-Down Regulation
Minimum-Component DC-DC Converters
Battery-Powered Applications
__________________Pin Configuration
TOP VIEW
3/5 (FB)
SHDN
( ) ARE FOR MAX1627
5V/3.3V or Adjustable, 100% Duty-Cycle,
____________________________Features
♦ Low Dropout Voltage
♦ 100% Maximum Duty Cycle
♦ Soft-Start Limits Start-Up Current
♦ Efficiency >90% (3mA to 2A Loads)
♦ Output Power >12.5W
♦ 90µA Max Quiescent Current
♦ 1µA Max Shutdown Current
♦ Up to 300kHz Switching Frequency
♦ 16.5V Max Input Voltage
♦ Output Voltage: 5V/3.3V (MAX1626)
Adjustable (MAX1627)
♦ Current-Limited Control Scheme
______________Ordering Information
TEMP. RANGE PIN-PACKAGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
V+
MAX1626
CSSHDN
P
3/5
REF
GND
EXT
OUT
Dice*
8 SO
Dice*
OUTPUT
3.3V
OUT
REF
1
2
3
4
MAX1626
MAX1627
SO
PART
MAX1626C/D
MAX1626ESA
MAX1627C/D
MAX1627ESA -40°C to +85°C 8 SO
* Dice are tested at TA= +25°C.
__________Typical Operating Circuit
INPUT
3.3V to 16.5V
8
GND
EXT
7
CS
6
5
V+
ON/OFF
MAX1626/MAX1627
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
5V/3.3V or Adjustable, 100% Duty-Cycle,
High-Efficiency, Step-Down DC-DC Controllers
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V+ to GND.......................................-0.3V, +17V
OUT, FB, 3/5, SHDN, REF, CS, EXT to GND...-0.3V, (V+ + 0.3V)
Maximum Current at REF (I
Maximum Current at EXT (I
Continuous Power Dissipation (T
SO (derate 5.88mW/°C above +70°C)..........................471mW
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.
)..........................................15mA
REF
) ..........................................50mA
EXT
= +70°C)
A
ELECTRICAL CHARACTERISTICS
(V+ = +3V to +16.5V, SHDN = 3/5 = 0V, TA= 0°C to +85°C, unless otherwise noted.)
Operating, no load
V
I+Supply Current into V+
V+ = SHDN = 16.5V (shutdown)
Circuit of Figure 1, 3/5 = V+ (Note 1)
OUT
Circuit of Figure 1, 3/5 = 0V (Note 1)
MAX1626, 3/5 = V+, output forced to 5V
OUT
MAX1627, includes hysteresis
MAX1627
CS
SHDN = 0V or V+
3/5 = 0V or V+
V+ = 5V
Output forced to 0V
Output in regulation
6.0V < V+ < 12.0V, I
30mA < I
LOAD
I
= 0µA
LOAD
REF
REF
≤ 100µA
0µA ≤ I
V+ = 3V to 16.5V, I
MAX1626/MAX1627
Output Voltage
OUT Input Current
CS Threshold Voltage
3/5 Input Voltage High
3/5 Input Voltage Low
3/5 Leakage Current
Minimum EXT Off Time
Reference Voltage
Operating Temperature Range
MAX1626ESA/MAX1627ESA............................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
CONDITIONS
70 90
4.85 5.00 5.15
3.20 3.30 3.40
81012
1.5 2.0 2.5
= 1A
LOAD
< 2.0A, V+ = 8V
= 0µA µV/V10 100REF Line Regulation
LOAD
UNITSMIN TYP MAXSYMBOLPARAMETER
1
V3.0 16.5V+Input Voltage Range
µA
V2.7 2.8Undervoltage Lockout
V
µA24 37 50I
V1.27 1.30 1.33FB Threshold Voltage
nA035FB Leakage Current
µA010CS Input Current
mV85 100 115V
V1.6SHDN Input Voltage High
V0.4SHDN Input Voltage Low
µA±1SHDN Input Current
VV+ - 0.5
V0.5
µA±1
Ω10EXT Resistance
µs
%100EXT Duty-Cycle Limit
mV/V5Line Regulation
mV/A15Load Regulation
V1.27 1.30 1.33V
mV410REF Load Regulation
2 _______________________________________________________________________________________
5V/3.3V or Adjustable, 100% Duty-Cycle,
High-Efficiency, Step-Down DC-DC Controllers
ELECTRICAL CHARACTERISTICS
(V+ = +3V to +16.5V, SHDN = 3/5 = 0V, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
CONDITIONS
Operating, no load
Supply Current into V+
Output Voltage
OUT Input Current
I
V
OUT
V+ = SHDN = 16.5V (shutdown)
Circuit of Figure 1, 3/5 = V+
OUT
Circuit of Figure 1, 3/5 = 0V
MAX1626, 3/5 = V+, output forced to 5V
OUT
MAX1627, includes hysteresis
MAX1627
I
= 0µA
LOAD
Note 1: V+ must exceed V
Note 2: Specifications from 0°C to -40°C are guaranteed by design, not production tested.
to maintain regulation.
OUT
4.80 5.20
3.16 3.44
100
2
MAX1626/MAX1627
UNITSMIN TYP MAXSYMBOLPARAMETER
V3.0 16.5V+Input Voltage
µA
V2.9Undervoltage Lockout
V
µA24 50I
V1.25 1.35FB Threshold Voltage
nA050FB Leakage Current
mV80 120CS Threshold Voltage
V1.25 1.35Reference
__________________________________________Typical Operating Characteristics
(Circuit of Figure 1, TA= +25°C, unless otherwise noted.)
DROPOUT VOLTAGE
0.45
0.40
0.35
0.30
0.25
0.20
0.15
DROPOUT VOLTAGE (V)
0.10
0.05
0
vs. LOAD CURRENT
3.3V SETTING
= +3.17V
V
OUT
0 0.5 1.0 1.5 2.0 2.5
LOAD (A)
_______________________________________________________________________________________ 3
5V SETTING
= +4.8V
V
OUT
MAX1626-11
EFFICIENCY vs. LOAD CURRENT
(V
= +3.3V)
100
90
A
80
70
60
50
40
EFFICIENCY (%)
30
20
10
CIRCUIT OF FIGURE 1
0
0.1m 100m 11m 10m 10
C
B
LOAD CURRENT (A)
OUT
D E F
A: V+ = +4.3V
B: V+ = +5V
C: V+ = +8V
D: V+ = +10V
E: V+ = +12V
F: V+ = +15V
MAX1626-05
EFFICIENCY (%)
EFFICIENCY vs. LOAD CURRENT
(V
= +5V)
100
90
A
80
70
60
50
40
30
20
10
CIRCUIT OF FIGURE 1
0
0.1m 100m 11m 10m 10
OUT
C
B
LOAD CURRENT (A)
D
E
A: V+ = +6V
B: V+ = +8V
C: V+ = +10V
D: V+ = +12V
E: V+ = +15V
MAX1626-03
5V/3.3V or Adjustable, 100% Duty-Cycle,
High-Efficiency, Step-Down DC-DC Controllers
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA= +25°C, unless otherwise noted.)
MAX1626 SHUTDOWN CURRENT
0.8
0.7
0.6
0.5
0.4
0.3
0.2
SHUTDOWN CURRENT (µA)
0.1
0
-60
MAX1626/MAX1627
vs. TEMPERATURE
APPLICATION CIRCUIT
SHUTDOWN CURRENT:
A: V+ = +15V
B: V+ = +10V
C: V+ = +4V
MAX1626 SHUTDOWN
CURRENT:
D: V+ = +16V
E: V+ = +4V
-20 0 204060 80 100120
-40
TEMPERATURE (°C)
A
MAX1626-04
B
C
D
EXT OFF TIME (µs)
E
140
MAX1626 EXT OFF TIME
vs. OUTPUT VOLTAGE
12
10
8
6
4
2
0
012345
3/5 = V+
3/5 = GND
OUTPUT VOLTAGE (V)
V+ = +5V
MAX1626-02
12
10
8
6
4
EXT OFF TIME (µs)
2
MAX1627 EXT OFF TIME
vs. FB PIN VOLTAGE
0
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
FB PIN VOLTAGE (V)
V+ = +5V
MAX1626-03
EXT RISE AND FALL TIMES
50
45
40
35
(ns)
30
FALL
25
AND t
20
RISE
t
15
10
5
0
-60 -40 -20 40 60 140
vs. TEMPERATURE
t
, V+ = +5V
FALL
t
RISE
C
= 1nF
EXT
3/5 = 0V
OUT = 50kHz, 0.3Vp-p
0
20 80
TEMPERATURE (°C)
t
RISE
, t
FALL
3.3V
,
, V+ = +5V
, V+ = +15V
DC
100 120
MAX1626-09
400
350
300
(ns)
250
FALL
200
AND t
150
RISE
t
100
50
EXT RISE AND FALL TIMES
vs. CAPACITANCE
t
, V+ = +15V
RISE
, V+ = +5V
t
FALL
t
, V+ = +5V
RISE
, V+ = +15V
t
0
0 2000 4000
CAPACITANCE (pF)
FALL
MAX1626
V+ QUIESCENT CURRENT
72
70
68
66
(µA)
Q
I
64
62
60
-60
vs. TEMPERATURE
V+ = +16V
V+ = +10V
V+ = +4V
3/5 = 0V
OUT FORCED TO 3.4V
-20 0 204060 80 100120
-40
TEMPERATURE (°C)
MAX1626-01
140
CS TRIP LEVEL vs. TEMPERATURE
115
OUT = 0V
110
105
100
95
CS TRIP LEVEL (mV)
90
85
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
4 _______________________________________________________________________________________
MAX1626-10
MAX1626-12
5V/3.3V or Adjustable, 100% Duty-Cycle,
High-Efficiency, Step-Down DC-DC Controllers
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA= +25°C, unless otherwise noted.)
MAX1626/MAX1627
REFERENCE OUTPUT VOLTAGE
vs. TEMPERATURE
1.310
1.305
1.300
1.295
1.290
1.285
REFERENCE OUTPUT VOLTAGE (V)
1.280
I
= 0µA
REF
= 50µA
I
REF
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
MAX1626 LOAD-TRANSIENT RESPONSE
A
I
REF
= 10µA
I
REF
= 100µA
MAX1626-15
MAX1626-13
MAX1626 LINE-TRANSIENT RESPONSE
A
MAX1626 SHUTDOWN RESPONSE TIME
AND SUPPLY CURRENT
A
B
C
V+ = 8V, V
A: OUT, 2V/div
B: SUPPLY CURRENT, 1A/div
C: SHDN, 5V/div
500µs/div
= 5V, LOAD = 1A
OUT
LINE-TRANSIENT RESPONSE
FROM 100% DUTY CYCLE
MAX1626-16
A
MAX1626-14
MAX1626-17
B
V+ = 8V, V
A: OUT, 50mV/div, 3.3V DC OFFSET
B: LOAD CURRENT, 1A/div
100µs/div
= 3.3V, LOAD = 30mA to 2A
OUT
_______________________________________________________________________________________
B
V
= 5V, LOAD = 1A, CIN = 33µF
OUT
A: OUT, 100mV/div, 5V DC OFFSET
B: V+ 6V to 12V, 2V/div
5ms/div
B
V
= 3.3V, LOAD = 1A, CIN = 47µF
OUT
A: OUT, 100mV/div, 3.3V DC OFFSET
B: V+ 3.3V to 15V, 5V/div
5ms/div
5
5V/3.3V or Adjustable, 100% Duty-Cycle,
High-Efficiency, Step-Down DC-DC Controllers
______________________________________________________________Pin Description
MAX1626
PIN
MAX1627
NAME
Sense input for fixed 5V or 3.3V output operation. OUT is internally connected to an
11
OUT
on-chip voltage divider (MAX1626). It does not supply current. Leave OUT unconnected during adjustable-output operation (MAX1627).
2—
—2
FB
3/5
Feedback Input for adjustable-output operation. Connect to an external voltage
divider between the output and GND (see the
3.3V or 5V Selection. Output voltage is set to 3.3V when this pin is low or 5V when it
is high.
Active-High Shutdown Input. Device is placed in shutdown when SHDN is driven
33
SHDN
high. In shutdown mode, the reference, output, and external MOSFET are turned off.
Connect to GND for normal operation.
MAX1626/MAX1627
V+
REF
1.3V Reference Output. Can source 100µA. Bypass with 0.1µF.44
Positive Supply Input. Bypass with 0.47µF.55
Current-Sense Input. Connect current-sense resistor between V+ and CS. External
66
CS
MOSFET is turned off when the voltage across the resistor equals the current-limit
trip level (around 100mV).
Gate Drive for External P-Channel MOSFET. EXT swings between V+ and GND.77
Ground88
C5
0.47µF
R
SENSE
0.04Ω
U1
LOGIC-LEVEL MOSFET
L1
22µH, 3A
L1: SUMIDA CDRH125-220
D1: NIHON NSQ03A03
U1: MORTOLA MMSF3PO2HD
INPUT
68µF LOW-ESR
TANTALUM
C4
0.1µF
C2
3/5
SHDN
REF
MAX1626
GND
C3
68µF LOW-ESR
TANTALUM
V+
CS
EXT
OUT
D1
EXT
GND
P
Figure 1. MAX1626 Typical Operating Circuit
OUTPUT
C1
220µF
LOW-ESR
TANTALUM
FUNCTION
Setting the Output Voltage
EXT REF
1.5V
MAX1626
MAX1627
MINIMUM ON-TIME
ONE-SHOT
TRIG
Q
Q
TRIG
MINIMUM OFF-TIME
ONE-SHOT
S
CURRENT-SENSE
COMPARATOR
REF
Q
R
Figure 2. Simplified Functional Diagram
ERROR
COMPARATOR
R2
R1
( ) MAX1627 ONLY
MAX1626 ONLY
section).
OUT
(FB)
R3
3/5
SHDN
V+
CS
6 _______________________________________________________________________________________
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