_______________General Description
The MAX777L/MAX778L/MAX779L are pulse-skipping DC-DC
converters that step up from low-voltage inputs (1V guaran-
teed). They require only three external components—an induc-
tor (typically 22µH) and two capacitors. The MAX777L delivers
a 5V output, the MAX778L generates pin-selectable voltages of
3.0V or 3.3V, and the MAX779L output can be adjusted from
2.5V to 6V through an external resistive divider.
The devices include an Active RectifierTM that eliminates the
need for an external catch diode, and permits regulation even
when the input is greater than the output. Also, unlike those in
other step-up converters, the MAX777L/MAX778L/MAX779L’s
Active RectifierTM turns off in the shutdown mode, disconnect-
ing the output from the source. This eliminates the current drain
associated with conventional step-up converters when off or in
shutdown.
High-frequency operation (up to 150kHz) allows the use of
small, surface-mount inductors with values of 10µH or less.
Supply current is 190µA under no load and only 20µA in stand-
by mode; supply voltage can range from 1V to 4.5V (1 to 3
cells). With a 2V input, the devices typically deliver 200mA at
5V, or 300mA at 3V.
For fully specified devices designed for step-up/step-down
applications (where the input can be above or below the out-
put), refer to the MAX877L/MAX878L/MAX879L data sheet.
________________________Applications
Single Battery-Cell (1V), Step-Up Voltage Conversion
Efficient, High-Power Step-Up Regulation from
Low Input Voltages
Pagers
Portable Instruments & Hand-Held Terminals
Notebook and Palmtop Computers
____________________________Features
♦1V to 4.5V Input Guarantees Start-Up Under Load
♦Up to 210mA Output
♦Load Fully Disconnected in Shutdown
♦82% Efficiency
♦Output in Regulation with Input Voltage above
Output Voltage
♦Internal 1A Power Switch and Active Rectifier
♦Adjustable Current Limit Allows Low-Cost
Inductors
♦190µA No Load Supply Current
♦20µA Shutdown Supply Current
♦3V/3.3V (MAX778L), 5V (MAX777L), and
Adjustable (MAX779L) Output Voltage
______________Ordering Information
Ordering Information continued at end of data sheet.
* Dice are specified at T
A
= +25°C, DC parameters only.
**Contact factory for availability and processing to MIL-STD-883.
MAX777L/MAX778L/MAX779L
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
________________________________________________________________
Maxim Integrated Products
1
1
2
3
4
DIP/SO
TOP VIEW
MAX777L
MAX778L
MAX779L
8
7
6
5
N.C. (MAX777L)*
SHDN
OUT
LX
ILIM
IN
AGND
PGND
* SEL FOR MAX778L, FB FOR MAX779L.
__________________Pin Configuration
INPUT
1V TO 4.5V
IN
ILIM
SHDN
100µF
OUTPUT
5V
AGND
MAX777L
LX
OUT
PGND
22µH
ON/OFF
22µF
1
2
7
43
6
5
__________Typical Operating Circuit
19-0186; Rev 2; 7/96
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
PART TEMP. RANGE PIN-PACKAGE
MAX777LCPA 0°C to +70°C 8 Plastic DIP
MAX777LCSA 0°C to +70°C 8 SO
MAX777LC/D 0°C to +70°C Dice*
MAX777LMJA -55°C to +125°C 8 CERDIP**
MAX777LESA -40°C to +85°C 8 SO
MAX777LEPA -40°C to +85°C 8 Plastic DIP
Active Rectifier is a trademark of Maxim Integrated Products.
EVALUATION KIT MANUAL
FOLLOWS DATA SHEET
MAX777L/MAX778L/MAX779L
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN = +2.5V, ILOAD = 0mA, L = 22µH, COUT = 100µF, SHDN and ILIM connected to IN, AGND connected to PGND, TA= TMIN to TMAX,
typical values are at TA= +25°C, unless otherwise noted.)
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.
Supply Voltage (IN to PGND).......................................0V to 4.5V
Output Short-Circuit Duration to PGND, AGND (Note 1)....30sec
Voltage Applied to:
LX (switch off).......................................................-0.3V to 4.5V
(switch on)....................................30sec short to IN or OUT
OUT, SHDN ...........................................................-0.3V to +7V
FB ...........................................................-0.3V to (OUT + 0.3V)
AGND to PGND........................................................-0.3V, +0.3V
Reverse Battery Current....................................................900mA
Continuous Power Dissipation (TA= +70°C)
Plastic DIP (derate 9.09mW/°C above +70°C) .............727mW
SO (derate 5.88mW/°C above +70°C)..........................471mW
CERDIP (derate 8.00mW/°C above +70°C)..................640mW
Operating Temperature Ranges:
MAX77_LC_A.......................................................0°C to +70°C
MAX77_LE_A....................................................-40°C to +85°C
MAX77_LMJA .................................................-55°C to +125°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10sec).............................+300°C
Note 1: The output may be shorted to ground if the package power dissipation is not exceeded.
PARAMETER
Output Voltage
MAX777L/MAX779L
(set to 5V)
(Note 6)
MIN TYP MAX
(Note 4)
ILOAD = 100mA
UNITS
SHDN Input Current
MAX77_LM
MAX77_LC, MAX77_LE
12 40
Output Voltage Range
(MAX779L) 2.5 6.0
µA
VIN < SHDN < 5V
V
20 35
15 100
4.80 5.00 5.20
nA
0V < SHDN < VIN
V
MAX777LC/
MAX779LC
Maximum Operating Voltage
Minimum Start-Up Voltage 1 V
4.5 V
Efficiency 82 %
No-Load Supply Current 190 310 µA
Shutdown Supply Current 20 30 µA
CONDITIONS
ILOAD = 0mA (switch off)
SHDN = 0V
MAX777LE/
MAX779LE
MAX777LM/
MAX779LM
(Notes 2, 3)
ILOAD < 10mA, TA= +25°C (Note 2)
Output Voltage
MAX778L
(Note 6)
MAX778LE 3.17 3.30 3.43
V
MAX778LC
SEL = 0V
MAX778LM
MAX778LE 2.88 3.00 3.12
MAX778LC
SEL = OPEN
MAX778LM
ILOAD ≤30mA, 1.1V ≤VIN ≤4.5V or
ILOAD ≤140mA, 1.8V ≤VIN ≤4.5V
ILOAD ≤30mA, 1.2V ≤VIN ≤4.5V or
ILOAD ≤130mA, 1.8V ≤VIN ≤4.5V
ILOAD ≤25mA, 1.25V ≤VIN ≤4.5V or
ILOAD ≤120mA, 1.8V ≤VIN ≤4.5V
ILOAD ≤50mA, 1.1V ≤VIN ≤3.3V or
ILOAD ≤210mA, 1.8V ≤VIN ≤3.3V
ILOAD ≤50mA, 1.2V ≤VIN ≤3.3V or
ILOAD ≤200mA, 1.8V ≤VIN ≤3.3V
ILOAD ≤50mA, 1.25V ≤VIN ≤3.3V or
ILOAD ≤180mA, 1.8V ≤VIN ≤3.3V
ILOAD ≤50mA, 1.1V ≤VIN ≤3V or
ILOAD ≤210mA, 1.8V ≤VIN ≤3V
ILOAD ≤50mA, 1.2V ≤VIN ≤3V or
ILOAD ≤200mA, 1.8V ≤VIN ≤3V
ILOAD ≤40mA, 1.25V ≤VIN ≤3V or
ILOAD ≤180mA, 1.8V ≤VIN ≤3V
MAX777L/MAX778L/MAX779L
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
_______________________________________________________________________________________ 3
Note 2: Output in regulation, VOUT = VOUT (nominal) ±4%.
Note 3: At high VIN to VOUT differentials, the maximum load current is limited by the maximum allowable power dissipation in the
package (see
Absolute Maximum Ratings
).
Note 4: Minimum value is production tested. Maximum value is guaranteed by design and is not production tested.
Note 5: VOUT is set to a target value of +5V by 0.1% external feedback resistors. VOUT is measured to be 5V ±2.5% to guarantee the
error comparator trip point.
Note 6: Start-Up guaranteed under these load conditions.
PARAMETER
Maximum Switch On Time
MIN TYP MAX
12.6
UNITS
Switch Saturation Voltage
µs
0.275
1.2
-0.3
µs
%/°C
Current Limit 1.0 A
Minimum Switch Off Time
0.33
0.50 V
2.2
4.0
0.21 V
5.9
0.31Rectifier Forward Voltage Drop
SHDN Threshold
0.50
Error-Comparator Trip Point 197.5 202.5 207.5
VIN/2 + 0.25
mV
V
FB Pin Bias Current
1.20 1.6
10 40 nA
Switch Off Leakage Current
SHDN Enable Delay
0.1 µA
150 µs
Rectifier Off Leakage Current 0.1 µA
CONDITIONS
VIN = 1V
ISW = 400mA
MAX777L, MAX779L
ISW = 600mA
ISW = 1000mA
MAX778
ISW = 400mA
VIN = 2.5V
VIN = 1.8V
ISW = 600mA
ISW = 1000mA
MAX779L, over operating input voltage (Note 5)
VIN = 1V to 4.5V
VIN = 2.5V
MAX779L, VFB = 0.3V
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +2.5V, ILOAD = 0mA, L = 22µH, COUT = 100µF, SHDN and ILIM connected to IN, AGND connected to PGND, TA= TMIN to TMAX,
typical values are at TA= +25°C, unless otherwise noted.)
Current-Limit Temperature
Coefficient
MAX777L/MAX778L/MAX779L
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
4 _______________________________________________________________________________________
__________________________________________Typical Operating Characteristics
(Typical Operating Circuit, TA= +25°C, unless otherwise noted).
50
12 5
SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE AND TEMPERATURE
60
MAX777-7
INPUT VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT (µA)
70
80
34
40
10
20
30
076
TA = +85°C
TA = 0°C
TA = -40°C
2.0
12 5
MAX778L
SHDN THRESHOLD VOLTAGE
vs. INPUT VOLTAGE AND TEMPERATURE
2.5
MAX777-8
INPUT VOLTAGE (V)
SHDN THRESHOLD VOLTAGE (V)
3.0
3.5
34
1.5
0.5
1.0
76
TA = +125°C
TA = -55°C
TA = +25°C
90
40
0.1 1 1000
MAX777L/MAX779L
EFFICIENCY vs. LOAD CURRENT
50
MAX777-1
LOAD CURRENT (mA)
EFFICIENCY (%)
60
70
80
10 100
30
VIN = 4V
VIN = 2.5V
VIN = 1.8V
VIN = 1.5V
VIN = 1.1V
VOUT = 5V 90
40
0.1 1 1000
MAX778L
EFFICIENCY vs. LOAD CURRENT
50
MAX777-2
LOAD CURRENT (mA)
EFFICIENCY (%)
60
70
80
10 100
30
VIN = 2.5V
VIN = 1.8V
VIN = 1.5V
VIN = 1.1V
VOUT = 3.3V OR 3.0V
300
50
0.5 1.0 2.5
MAX777L/MAX779L
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
100
MAX777-4
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
150
200
250
1.5 2.0
0
VOUT = 5V 350
50
0.5 1.0
MAX778L
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
100
MAX777-5
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
150
200
250
1.5 2.0
0
VOUT = 3.3V
300
300
200
12 5
NO-LOAD SUPPLY CURRENT
vs. VOLTAGE AND TEMPERATURE
220
MAX777-6
SUPPLY VOLTAGE (V)
NO-LOAD SUPPLY CURRENT (µA)
240
260
280
34
180
(SWITCH = OFF)
120
140
160
100 76
TA = -40°C
TA = +25°C
TA = 0°C
TA = +85°C
MAX777L/MAX778L/MAX779L
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
_______________________________________________________________________________________ 5
A: IOUT, 200mA/div, 0mA to 200mA
B: VOUT, 50mV/div, AC COUPLED
MAX778L, VOUT = 3.3V, VIN = 2.5V
LOAD-TRANSIENT RESPONSE
A
B
2ms/div
_____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA= +25°C, unless otherwise noted.)
A: VIN, 1V/div, 1.8V to 3.3V
B: VOUT, 100mV/div, AC-COUPLED, IOUT = 240mA
MAX778L, VOUT = 3.3V
LINE-TRANSIENT RESPONSE
A
B
2ms/div
A: SWITCH VOLTAGE (LX PIN), 2V/div
B: INDUCTOR CURRENT, 0.5A/div
C: OUTPUT VOLTAGE RIPPLE, 50mV/div, AC COUPLED
MAX777L, VIN = 1.5V, IOUT = 100mA
SWITCHING WAVEFORMS,
CONTINUOUS CONDUCTION
A
B
C
0mA
5µs/div
A: SWITCH VOLTAGE (LX PIN), 2V/div
B: INDUCTOR CURRENT, 0.5A/div
C: OUTPUT VOLTAGE RIPPLE, 50mV/div, AC COUPLED
MAX777L, VIN = 3V, IOUT = 70mA
SWITCHING WAVEFORMS,
DISCONTINUOUS CONDUCTION
A
B
C
2µs/div
MAX777L/MAX778L/MAX779L
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
6 _______________________________________________________________________________________
A: SHDN, 2V/div
B: VOUT, 1V/div
VOUT = 3V
MAX778L
START-UP TIME
A
B
10ms/div
_____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 1, TA= +25°C, unless otherwise noted.)
NAME FUNCTION
1ILIM Sets switch current-limit input. Connect to IN for 1A current limit. A resistor from ILIM to IN sets lower
peak inductor currents.
2 IN Input from battery
3 AGND Analog ground. Not internally connected to PGND.
PIN
4 PGND Power ground. Must be low impedance; solder directly to ground plane or star ground. Connect to
AGND, close to the device.
5 LX Collector of 1A NPN power switch and emitter of Active Rectifier PNP.
6 OUT Voltage output. Connect filter capacitor close to pin.
7SHDN Shutdown input disables power supply when low. Also disconnects load from input. Threshold is set at
VIN/2.
8
N.C.
(MAX777L) No connect—not internally connected.
SEL
(MAX778L) Selects the main output voltage. 3.3V when hard-wired to AGND, 3.0V when left open.
______________________________________________________________Pin Description
FB
(MAX779L) Feedback input for adjustable-output operation. Connect to an external voltage divider between VOUT
and AGND.
_______________Detailed Description
Operating Principle
The MAX777L/MAX778L/MAX779L combine a switch-
mode regulator with an NPN bipolar switch, current
limit, precision voltage reference, and active rectifier—
all in a single monolithic device. In shutdown mode,
the internal rectifier is completely turned off and dis-
connects the load from the source. Only two external
components are required in addition to the input
bypass capacitor: a 22µH inductor and a 100µF filter
capacitor.
A minimum off-time, current-limited, pulse-frequency-
modulation (PFM) control scheme combines the advan-
tages of pulse width modulation (PWM) (high output
power and efficiency) with those of a traditional PFM
pulse skipper (low quiescent currents).
External conditions (inductor value, load, and input volt-
age) determine the way the converter operates, as follows:
At light loads, the current through the inductor starts at
zero, rises to a peak value, and drops down to zero in
each cycle (discontinuous-conduction mode). In this
case, the switching frequency is governed by a pair of
one-shots that set a maximum on-time inversely propor-
tional to VIN [tON = 8.8/(VIN - 0.25)] and a minimum off-
time (1.3µs for MAX777L/MAX779L and 2.3µs for
MAX778L). With a 22µH inductor, LX’s peak current is
about 400mA and is independent of input voltage.
Efficiency at light loads is improved because of lower
peak currents.
At very light loads, more energy is stored in the coil
than is required by the load in each cycle. The converter
regulates by skipping entire cycles. Efficiency is typically
65% to 75% in the pulse-skipping mode. Pulse-skipping
waveforms can be irregular, and the output waveform
contains a low-frequency component. Larger, low equiv-
alent series resistance (ESR) filter capacitors can help
reduce the ripple voltage if needed.
MAX777L/MAX778L/MAX779L
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
_______________________________________________________________________________________ 7
MAX778L
DELAY
TIMER
tOFF
DELAY
TIMER
tON
VREF 0.2025V
SHUTDOWN
CONTROL
SHDN7
ACTIVE RECTIFIER
RECTIFIER
CONTROL
OUT
PGND
AGND
3
SEL 8
4
6
100µF
VOUT
100µF
VIN 22µH
RLIM
SWITCH
DRIVER
LX
ILIM
IN 21
1 : N
Figure 1. MAX778L Block Diagram
MAX777L/MAX778L/MAX779L
At heavy loads above approximately 100mA, the con-
verter enters continuous-conduction mode, where cur-
rent always flows in the inductor. The switch-on state is
controlled cycle-by-cycle by either the maximum tON
time or the switch’s preset current limit. As a result, the
switch's current rating is not exceeded and the inductor
is not saturated. At very heavy loads, the inductor cur-
rent self-oscillates between this peak current limit and
some lower value governed by the minimum off-time,
the inductance value, and the input/output differential.
With ILIM shorted to IN, the peak switch current of the
internal NPN power switch is set to 1A. The peak switch
current can be set to a lower value by connecting a
resistor between ILIM and IN (see
Current Limit
sec-
tion). This enables the use of physically smaller induc-
tors with lower saturation-current ratings. At 1A, the
switch voltage drop (VSW) is about 500mV. VSW
decreases to about 250mV at 0.1A.
Conventional PWM converters generate constant-fre-
quency switching noise, while this architecture pro-
duces variable-frequency switching noise. However,
the noise does not exceed the current limit times the fil-
ter-capacitor ESR, unlike conventional pulse-skippers.
Step-Down Mode
If the input voltage exceeds the output voltage, the
MAX777L/MAX778L/MAX779L behave as “switched”
linear regulators. If the output voltage starts to drop, the
switch turns on and energy is stored in the coil, as in
normal step-up mode. After the switch turns off, the
voltage at LX flies high. The active rectifier turns on
when LX rises above VIN. As in a linear regulator, the
voltage difference between VIN and VOUT appears
across the rectifier (actually a PNP transistor) until the
current goes to zero and the rectifier turns off. At high
VIN to VOUT differentials, the maximum load current is
limited by the maximum allowable power dissipation in
the package. For fully specified buck/boost converters,
refer to the data sheet for the pin-compatible
MAX877L/MAX878L/MAX879L.
Active Rectifier
The internal active rectifier of the MAX777L/MAX778L/
MAX779L replaces the external Schottky catch diode in
normal boost operation. The rectifier consists of a PNP
pass transistor and a unique control circuit which, in
shutdown mode, entirely disconnects the load from the
source. This is a distinct advantage over standard
boost topologies, since it prevents battery drain in shut-
down.
The active rectifier also acts as a zero-dropout regulator
if the input exceeds the regulated output. This allows the
MAX777L/MAX778L/MAX779L to act as buck/boost
converters. Useful in battery-powered applications,
where the battery voltage may initially exceed the output
voltage, the converters will regulate down to the output
voltage and seamlessly switch into boost mode as the
input drops below the output voltage. The pin-compati-
ble MAX877L/MAX878L/MAX879L are fully specified
buck/boost converters with higher specified output cur-
rents than the MAX777L/MAX778L/MAX779L.
Shutdown
Shutdown (SHDN) is a high-impedance, active-low
input. Connect SHDN to VIN for normal operation.
Keeping SHDN at ground holds the converters in shut-
down mode. Since the active rectifier is turned off in
shutdown mode, the path from input to load is cut, and
the output effectively drops to 0V. The supply current in
the shutdown state ranges from 4µA at VIN = 1V to
50µA at VIN = 4.5V. The shutdown circuit threshold is
set nominally to VIN/2 + 250mV. When SHDN is below
this threshold, the device is shut down and is enabled
with SHDN above the threshold. When driven from
external logic, SHDN can be driven to a higher voltage
than VIN.
Current Limit
Connecting ILIM to IN sets an LX current limit of 1A. For
smaller output power levels that do not require the max-
imum peak current, the peak inductor current can be
reduced to optimize overall efficiency and to allow very
small, low-cost coils with lower current ratings. See also
the
Inductor Selection
section.
Reduce the MAX777L/MAX778L/MAX779L peak induc-
tor current by connecting a resistor between ILIM and
IN. See Figure 2 to select the resistor.
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
8 _______________________________________________________________________________________
600
028
CURRENT-LIMIT RESISTOR
vs. PEAK INDUCTOR CURRENT
800
MAX777-FG02
RESISTOR VALUE (kΩ)
PEAK INDUCTOR CURRENT (mA)
1000
1200
46
400
0
200
12 1410
VIN = 2.5V
Figure 2. Current-Limit Resistor vs. Current Limit
Output Voltage Selection
The output voltage of the MAX777L is fixed at 5V. The
MAX778L output voltage can be set to 3V by leaving the
SEL pin open. Connect SEL to AGND for 3.3V operation.
The MAX779L’s output voltage is set by two resistors,
R1 and R2 (Figure 3), which form a voltage divider
between the output and the FB pin. The output voltage
can be set from 2.5V to 6.0V by the equation:
VOUT = (0.2025) [(R1 + R2)/R2]
To simplify the resistor selection:
R1 = (R2)[(VOUT/0.2025) - 1]
Since the input current at FB is 40nA maximum, large val-
ues (10kΩto 50k Ωfor R2) can be used with no significant
loss of accuracy. For 1% error, the current through R2
should be at least 100 times FB’s bias current.
When large values are used for the feedback resistors
(R1 > 50kΩ), stray output impedance at FB can add
“lag” to the feedback response, destabilizing the regula-
tor and creating a larger ripple at the output. Lead
lengths and circuit board traces at the FB node should be
kept short. Reduce ripple by adding a “lead” compensa-
tion capacitor (C3, 100pF to 50nF) in parallel with R1.
__________Applications Information
The
Typical Operating Circuit
shows a MAX777L step-
up application circuit. This circuit starts up and oper-
ates with inputs ranging from 1.0V to 4.5V. Start-up time
is a function of the load, typically less than 5ms. Output
current capability is a function of the input voltage. See
Typical Operating Characteristics
.
Inductor Selection
The 22µH inductor shown in the
Typical Operating
Circuit
is sufficient for most MAX777L/MAX778L/
MAX779L designs. Other inductor values ranging from
10µH to 47µH are also suitable. The inductor should
have a saturation rating equal to or greater than the
peak switch-current limit, which is 1A without an exter-
nal current limit (ILIM connected to IN). It is acceptable
to operate the inductor at 120% of its saturation rating;
however, this will reduce efficiency. For highest effi-
ciency, use an inductor with a low DC resistance,
preferably under 0.2Ω. Table 1 lists suggested inductor
suppliers.
Capacitor Selection
The 100µF, 10V surface-mount tantalum (SMT) output
capacitor shown in the
Typical Operating Circuit
will
provide a 20mV output ripple or less, stepping up from
2V to 3.3V at 200mA. Smaller capacitors, down to 10µF,
are acceptable for light loads or in applications that tol-
erate higher output ripple. The input capacitor may be
omitted if the input lead length is less than 2 inches
(5cm) or if the loads are small.
The primary factor in selecting both the output and
input filter capacitor is low ESR. The ESR of both
bypass and filter capacitors affects efficiency. Optimize
performance by increasing filter capacitors or using
specialized low-ESR capacitors. The smallest low-ESR
SMT tantalum capacitors currently available are
Sprague 595D or 695D series. Sanyo OS-CON organic
semiconductor through-hole capacitors also exhibit
very low ESR, are rated for the wide temperature range,
and are particularly useful for operation at cold temper-
atures. Table 1 lists suggested capacitor suppliers.
Layout
The MAX777L/MAX778L/MAX779L’s high peak currents
and high-frequency operation make PC layout impor-
tant for minimum ground bounce and noise. Locate
input bypass and output filter capacitors close to the
device pins. All connections to the FB pin (MAX779L)
should also be kept as short as possible. A ground
plane is recommended. Solder AGND (pin 3) and
PGND (pin 4), directly to the ground plane. Refer to the
MAX777L/MAX778L/MAX779L evaluation kit (EV kit)
manual for a suggested surface-mount layout.
MAX777L/MAX778L/MAX779L
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
_______________________________________________________________________________________ 9
SHDN
PGND
MAX779L
OUT
AGND
7
1
34
8
6
LI
22µH
5LX
FB
2IN
ILIM
VIN
C1
22µF
R1 C3
C2
100µF
VOUT
R2
Figure 3. MAX779L Adjustable Voltage
MAX777L/MAX778L/MAX779L
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
10 ______________________________________________________________________________________
Table 1. Component Suppliers
PRODUCTION METHOD INDUCTORS CAPACITORS
Miniature
Through-Hole Sumida
RCH654-220
Low-Cost
Through-Hole
Nichicon
PL series low-ESR electrolytic
United Chemi-Con,
LXF series
Surface Mount
Sprague 595D
Sprague 695D
Matsuo
267 series
AVX
TPS series
Sumida
CD54-220 (22µH)
Murata-Erie
LQHYN1501K04M00-D5
(15µH)
Coiltronics
CTX20-1
Coilcraft
PCH-27-223
Sanyo OS-CON
low-ESR organic semiconductor
AVX USA: (803) 946-0690
(800) 282-4975, FAX (803) 626-3123
Coiltronics USA: (561) 241-7876, FAX (561) 241-9339
Matsuo USA: (714) 969-2491, FAX (714) 960-6492
Murata-Erie USA: (814) 237-1431
(800) 831-9172, FAX (814) 238-0490
Nichicon USA: (847) 843-7500
Sanyo USA: (619) 661-6835, FAX (847) 843-2798
Japan: (81) 7-2070-6306, FAX (81) 7-2070-1174
Sprague USA: (603) 224-1961, FAX (603) 224-1430
Sumida USA: (847) 956-0666, FAX (847) 956-0702
Japan: (81) 3-3607-5111, FAX (81) 3-3607-5144
United Chemi-Con USA: (714) 255-9500, FAX (714) 255-9400
___________________Chip Topography
MAX777L/MAX778L/MAX779L
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
______________________________________________________________________________________ 11
TRANSISTOR COUNT: 170;
SUBSTRATE CONNECTED TO AGND.
SHDN
OUT
IN
AGND
PGND
ILIM VREF FB
LX
0.084"
(2.134mm)
0.068"
(1.727mm)
_Ordering Information (continued)
PART TEMP. RANGE PIN-PACKAGE
MAX778LCPA 0°C to +70°C 8 Plastic DIP
MAX778LCSA 0°C to +70°C 8 SO
MAX778LC/D 0°C to +70°C Dice*
MAX778LMJA -55°C to +125°C 8 CERDIP**
MAX778LESA -40°C to +85°C 8 SO
MAX778LEPA -40°C to +85°C 8 Plastic DIP
MAX779LCPA 8 Plastic DIP
MAX779LCSA 0°C to +70°C 8 SO
MAX779LC/D 0°C to +70°C Dice*
MAX779LEPA -40°C to +85°C 8 Plastic DIP
MAX779LESA -40°C to +85°C 8 SO
MAX779LMJA -55°C to +125°C 8 CERDIP**
0°C to +70°C
* Dice are specified at T
A
= +25°C, DC parameters only.
**Contact factory for availability and processing to MIL-STD-883.
MAX777L/MAX778L/MAX779L
Low-Voltage Input, 3V/3.3V/5V/
Adjustable Output, Step-Up DC-DC Converters
________________________________________________________Package Information
DIM
A
A1
A2
A3
B
B1
C
D1
E
E1
e
eA
eB
L
MIN
–
0.015
0.125
0.055
0.016
0.045
0.008
0.005
0.300
0.240
0.100
0.300
–
0.115
MAX
0.200
–
0.175
0.080
0.022
0.065
0.012
0.080
0.325
0.310
–
–
0.400
0.150
MIN
–
0.38
3.18
1.40
0.41
1.14
0.20
0.13
7.62
6.10
2.54
7.62
–
2.92
MAX
5.08
–
4.45
2.03
0.56
1.65
0.30
2.03
8.26
7.87
–
–
10.16
3.81
INCHES MILLIMETERS
Plastic DIP
PLASTIC
DUAL-IN-LINE
PACKAGE
(0.300 in.)
DIM
D
D
D
D
D
D
PKG.
P
P
P
P
P
N
MIN
0.348
0.735
0.745
0.885
1.015
1.14
MAX
0.390
0.765
0.765
0.915
1.045
1.265
MIN
8.84
18.67
18.92
22.48
25.78
28.96
MAX
9.91
19.43
19.43
23.24
26.54
32.13
INCHES MILLIMETERS
PINS
8
14
16
18
20
24
C
AA2
E1
D
E
eA
eB
A3
B1
B
0° - 15°
A1
L
D1
e
21-0043A
DIM
A
A1
B
C
E
e
H
L
MIN
0.053
0.004
0.014
0.007
0.150
0.228
0.016
MAX
0.069
0.010
0.019
0.010
0.157
0.244
0.050
MIN
1.35
0.10
0.35
0.19
3.80
5.80
0.40
MAX
1.75
0.25
0.49
0.25
4.00
6.20
1.27
INCHES MILLIMETERS
21-0041A
Narrow SO
SMALL-OUTLINE
PACKAGE
(0.150 in.)
DIM
D
D
D
MIN
0.189
0.337
0.386
MAX
0.197
0.344
0.394
MIN
4.80
8.55
9.80
MAX
5.00
8.75
10.00
INCHES MILLIMETERS
PINS
8
14
16
1.270.050
L
0°-8°
HE
D
e
A
A1 C
0.101mm
0.004in.
B
12 ______________________________________________________________________________________
