Rainbow Electronics MAX1775 User Manual
General Description
The MAX1775 is a dual, step-down DC-DC converter
that generates both the main (+3.3V at over 2A) and
core (+1.8V at up to 1.5A) supplies for a complete
power solution for PDAs, subnotebooks, and other
hand-held devices. The main output is adjustable from
+1.25V to +5.5V. The core output is adjustable from 1V
to 5V. Both switching converters operate at up to
1.25MHz for small external components and use synchronous rectifiers to achieve efficiencies up to 95%.
Operation with up to 100% duty cycle provides the lowest possible dropout voltage to extend useful battery
life.
The MAX1775 accepts inputs from +2.7V up to +28V,
allowing use with many popular battery configurations as
well as AC-DC wall adapters. Digital soft-start reduces
battery current surges at power-up. Both the main and
core converters have separate shutdown inputs. The
MAX1775 comes in a small 16-pin QSOP package.
The MAX1775 evaluation kit is available to help reduce
design time.
________________________Applications
Hand-Held Computers
PDAs
Internet Access Tablets
POS Terminals
Subnotebooks
Features
♦ Dual, High-Efficiency, Synchronous Rectified
Step-Down Converter
♦ Main Power
Adjustable from +1.25V to +5.5V
Over 2A Load Current
Up to 95% Efficiency
♦ Core Power
Adjustable from 1V to 5V
Internal Switches
Up to 1.5A Load Current
Up to 92% Efficiency
♦ 100% (max) Duty Cycle
♦ Up to 1.25MHz Switching Frequency
♦ Input Voltage Range from +2.7V to +28V
♦ 170µA Quiescent Current
♦ 5µA Shutdown Current
♦ Digital Soft-Start
♦ Independent Shutdown Inputs
MAX1775
Dual-Output Step-Down
DC-DC Converter for PDA/Palmtop Computers
________________________________________________________________ Maxim Integrated Products 1
Pin Configuration
19-1811; Rev 1; 8/01
EVA
LUA
TIO
N
KIT
AVA
ILA
B
LE
Ordering Information
Typical Operating Circuit
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.
PART TEMP. RANGE PIN-PACKAGE
MAX1775EEE -40°C to +85°C 16 QSOP
IN 2.7V TO 5.5V (28V IN CASCADE)
IN
CVH
MAX1775
INC
PDRV
NDRV
CS+
CS-
FBM
LXC
FBC
CORE
1.8V
1.5A
TOP VIEW
ON
OFF
OFF
SHDNM
SHDNC
CVL
REF
PGND
GND
ON
1
SHDNM LXC
2
SHDNC
PGND
3
MAX1775
4
NDRV
CVL
5
IN
6
PDRV
7
CVH
8
16 QSOP
16
15
INC
14
GND
13
FBC
12
CS-
CS+
11
10
FBM
9
REF
MAIN
3.3V
OVER 2A
MAX1775
Dual-Output Step-Down
DC-DC Converter for PDA/Palmtop Computers
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN= +12V, V
MAIN
= V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V, Circuit of Figure 4, TA= 0°C to +85°C, unless otherwise noted.
Typical values are at T
A
= +25°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.
IN, SHDNM, CVH to GND.......................................-0.3V to +30V
IN to CVH, PDRV ......................................................-0.3V to +6V
PDRV to GND..................................(V
CVH
- 0.3V) to (VIN+ 0.3V)
PGND to GND .......................................................-0.3V to +0.3V
All Other Pins to GND...............................................-0.3V to +6V
Core Output Short Circuit...........................................Continuous
Continuous Power Dissipation
16-Pin QSOP (derate 7.1mW/°C above +70°C)..........571mW
Operating Temperature .......................................-40°C to +85°C
Storage Temperature.........................................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
(
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Voltage V
Input Quiescent Supply Current I
CS- Quiescent Supply Current ICS-
Core Regulator Quiescent
Supply Current
IN Shutdown Supply Current SHDNM = SHDNC = GND 5 30 µA
MAIN REGULATOR
Main Output Voltage Adjust
Range
FBM Regulation Threshold V
FBM Input Current I
Current-Limit Threshold V
Minimum Current-Limit
Threshold
Valley Current Threshold V
Zero Current Threshold V
PDRV, NDRV Gate Drive
Resistance
CS- to CVL Switch Resistance I
PDRV, NDRV Dead Time 50 ns
Maximum Duty Cycle 100 %
Minimum On-Time 200 400 650 ns
Minimum Off-Time 200 400 650 ns
IN
IN
I
INC
FBM
FBM
CLM
V
MIN
VALLEYVCS+
ZERO
V
= +1.5V, V
FBM
V
V
V
V
V
V
V
V
V
V
V
= V
SHDNM
= +1.5V, V
FBM
= V
SHDNM
= +1.5V, V
FBM
= V
SHDNM
C S + - C S - )
FBM
CS+
CS+
CS+
CS-
CVL
= 0 to + 60m V , V
= +1.3V -0.1 0.1 µA
- V
CS-
- V
CS-
- V
CS-
- V
CS-
= +3.3V, I
= 50mA 4.5 8 Ω
2.7 28 V
= +1.5V,
FBC
SHDNC
FBC
SHDNC
FBC
SHDNC
= +3.3V
= +1.5V,
= +3.3V
= +1.5V,
= +3.3V
15 30 µA
110 220 µA
60 120 µA
1.25 5.5 V
= + 2.7V to + 28V 1.21 1.25 1.29 V
IN
60 80 100 mV
61524mV
40 50 60 mV
015mV
= 50mA 2 4.4 Ω
LOAD
MAX1775
Dual-Output Step-Down
DC-DC Converter for PDA/Palmtop Computers
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VIN= +12V, V
MAIN
= V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V, Circuit of Figure 4, TA= 0°C to +85°C, unless otherwise noted.
Typical values are at T
A
= +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
CORE REGULATOR
Input Voltage Range V
INC Undervoltage Lockout
Core Output Voltage Adjust
Range
Maximum Core Load Current (Note 1) 1 1.5 A
FBC Regulation Threshold V
FBC Input Current I
Dropout Voltage (INC to LXC) I
LXC Leakage Current I
LXC P-Channel, N-Channel
On-Resistance
LXC P-Channel Current Limit I
LXC P-Channel Minimum
Current
LXC N-Channel Valley Current 900 1400 2400 mA
LXC N-Channel Zero-Crossing
Current
LXC Dead Time 50 ns
Maximum Duty Cycle 100 %
Minimum On-Time 170 400 670 ns
Minimum Off-Time 170 400 670 ns
REFERENCE
Reference Voltage V
Reference Load Regulation I
Reference Line Regulation VCS- = +2.5V to +5.5V, I
Reference Sink Current I
CVL, CVH REGULATORS
CVL Output Voltage V
CVL Switchover Threshold V
CVH Output Voltage V
CVH Switchover Threshold V
CVL Undervoltage Lockout
INC
FBC
FBC
LXC
CLC
REF
REF
CVL
CVH
IN
2.6 5.5 V
V
rising 2.40 2.47 2.55
INC
falling 2.30 2.37 2.45
V
INC
1.0 5.0 V
V
= +2.5 to +5.5V, I
INC
V
= +1.3V -0.1 0.1 µA
FBC
= 400mA 0.1 0.25 V
OUTC
V
= +5.5V, V
INC
= 0 to +5.5V -10 10 µA
LXC
= 0 to 200mA 0.97 1.0 1.03 V
OUTC
0.25 0.5 Ω
1200 1800 3000 mA
100 200 400 mA
40 110 170 mA
1.23 1.25 1.27 V
= 0 to 50µA 10 mV
REF
= 50µA 5 mV
REF
10 µA
I
= 50mA, V
CVL
I
= 50mA, VCS- = +3.3V 3.2
CVL
rising, hysteresis = 100mV (typ) 2.40 2.47 2.55 V
CS-
VIN = +4V, I
VIN = +12V, I
= +2.7V, VCS- = 0 2.6 2.8 3.1
IN
= 25mA V
CVH
= 50mA V
CVH
IN
IN
- 3.4 V
- 4.3 V
VIN rising, hysteresis = 350mV (typ) 5.5 V
V
rising 2.40 2.47 2.55
CVL
falling 2.30 2.37 2.45
V
CVL
IN
IN
- 2.8
- 3.7
V
V
V
V
MAX1775
Dual-Output Step-Down
DC-DC Converter for PDA/Palmtop Computers
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VIN= +12V, V
MAIN
= V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V, Circuit of Figure 4, TA= 0°C to +85°C, unless otherwise noted.
Typical values are at T
A
= +25°C.)
ELECTRICAL CHARACTERISTICS
(VIN= +12V, V
MAIN
= V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V, Circuit of Figure 4, TA-40°C to +85°C, unless otherwise noted.)
(Note 2)
(
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
LOGIC INPUTS
SHDNM, SHDNC Input Low
Voltage
SHDNM, SHDNC Input High
Voltage
SHDNM, SHDNC Input Low
Current
SHDNC Input High Current V
SHDNM Input High Current
PARAMETER SYMBOL CONDITIONS MIN MAX UNITS
Input Voltage V
Input Quiescent Supply Current I
CS- Quiescent Supply Current I
Core Regulator Quiescent
Supply Current
IN Shutdown Supply Current SHDNM = SHDNC = GND 30 µA
MAIN REGULATOR
Main Output Voltage Adjust
Range
CS-
I
INC
IN
IN
2.0 V
SHDNM = SHDNC = GND -1 1 µA
= +5.5V 5 µA
SHDNC
V
V
= +5V 2
SHDNM
= +28V 15 30
SHDNM
2.7 28 V
V
FBM
V
SHDNM
V
FBM
V
SHDNM
V
FBM
V
SHDNM
= +1.5V, V
= V
= +1.5V, V
= V
= +1.5V, V
= V
FBC
SHDNC
FBC
SHDNC
FBC
SHDNC
= +1.5V,
= +3.3V
= +1.5V,
= +3.3V
= +1.5V,
= +3.3V
1.25 5.5 V
0.4 V
µA
30 µA
220 µA
120 µA
FBM Regulation Threshold V
FBM Input Current I
FBM
FBM
Current-Limit Threshold V
M i ni m um C ur r ent- Li m i t Thr eshol d V
Valley Current Threshold V
Zero Current Threshold V
PDRV, NDRV Gate Drive
Resistance
CS- to CVL Switch Resistance I
CL
V
C S + - C S - )
V
FBM
V
CS+
CS+
CS+
CS+
V
CS-
CVL
= 0 to + 60m V , V
= + 2.7V to + 28V 1.21 1.29 V
I N
= +1.3V -0.1 0.1 µA
- V
- V
- V
- V
CS-
CS-
CS-
CS-
60 100 mV
624mV
40 60 mV
015mV
= +3.3V 4.4 Ω
= 50mA 8 Ω
MAX1775
Dual-Output Step-Down
DC-DC Converter for PDA/Palmtop Computers
_______________________________________________________________________________________ 5
ELECTRICAL CHARACTERISTICS (continued)
(VIN= +12V, V
MAIN
= V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V, Circuit of Figure 4, TA-40°C to +85°C, unless otherwise noted.)
(Note 2)
PARAMETER SYMBOL CONDITIONS MIN MAX UNITS
Maximum Duty Cycle 100 %
Minimum On-Time 200 650 ns
Minimum Off-Time 200 650 ns
CORE REGULATOR
Input Voltage Range V
INC Undervoltage Lockout
Core Output Voltage Adjust
Range
Maximum Core Load Current (Note 1) 1 A
FBC Regulation Threshold V
FBC Input Current I
Dropout Voltage (INC to LXC) I
LXC Leakage Current I
LXC P-Channel, N-Channel
On-Resistance
LXC P-Channel Current Limit 1200 3050 mA
LXC P-Channel Minimum
Current
LXC N-Channel Valley Current 880 2450 mA
LXC N-Channel Zero-Crossing
Current
Maximum Duty Cycle 100 %
Minimum On-Time 150 670 ns
Minimum Off-Time 150 670 ns
REFERENCE
Reference Voltage V
Reference Load Regulation I
Reference Line Regulation
Reference Sink Current I
CVL, CVH REGULATORS
CVL Output Voltage V
CVH Output Voltage V
CVL Undervoltage Lockout
INC
FBC
FBC
LXC
REF
REF
CVL
CVH
V
INC
V
INC
V
INC
V
FBC
OUTC
V
INC
REF
V
CS-
I
REF
I
CVL
VIN = +4V, I
VIN = +12V, I
V
CVL
V
CVL
2.6 5.5 V
rising 2.39 2.55
falling 2.29 2.45
1.0 5.0 V
= +2.5V to +5.5V, I
= 0 to 200mA 0.97 1.03 V
OUTC
= +1.3V -0.1 0.1 µA
= 400mA 0.2 V
= +5.5V, V
= 0 to +5.5V -10 10 µA
LXC
0.5 Ω
100 400 mA
35 175 mA
1.22 1.27 V
= 0 to 50µA 10 mV
= +2.5V to +5.5V,
= 50µA
5mV
10 µA
= 50mA, V
= +2.7V, V
IN
= 25mA V
CVH
= 50mA VIN - 3.7
CVH
= 0 2.6 3.1 V
CS-
IN
- 2.8
rising 2.40 2.55
falling 2.30 2.45
V
V
V
Loading...