Rainbow Electronics MAX1774 User Manual
General Description
The MAX1774 is a complete power-supply solution for
PDAs and other hand-held devices. It integrates two
high-efficiency step-down converters, a boost converter
for backup battery regulation, and four voltage detectors in a small 32-pin QFN or 28-pin QSOP package.
The MAX1774 accepts inputs from +2.7V to +28V and
provides an adjustable main output from 1.25V to 5.5V
at over 2A. The secondary core converter delivers an
adjustable voltage from 1V to 5V and can deliver up to
1.5A. Both the main and core regulators have separate
shutdown inputs.
When the AC adapter power is removed, an external Pchannel MOSFET switches input to the main battery.
When the main battery is low, the backup step-up converter sustains the main output voltage. When the backup battery can no longer deliver the required load, the
system shuts down safely to prevent damage. Four onboard voltage detectors monitor the status of the AC
adapter power, main battery, and backup battery.
The MAX1774 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 Converters
♦ Thin, Small (1mm High) QFN Package
♦ Step-Up Converter for Backup Battery
♦ 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 91% Efficiency
♦ Automatic Main Battery Switchover
♦ 100% (max) Duty Cycle
♦ Up to 1.25MHz Switching Frequency
♦ Input Voltage Range from +2.7V to +28V
♦ Four Low-Voltage Detectors
♦ 170µA Quiescent Current
♦ 8µA Shutdown Current
♦ Digital Soft-Start
♦ Independent Shutdown Inputs
MAX1774
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
________________________________________________________________ Maxim Integrated Products 1
32
31
30
29
28
27
26
BKUP
SHDNC
SHDNM
N.C.
LXC
INS
LBO
25 N.C.
9
10
11
12
13
14
15
LXB
LXB2
BIN
BKOFF
ACI
DBI
LBI
16REF
17
18
19
20
21
22
23
N.C.
GND
GND
GND
GND
FBM
CS+
CS-
FBC
GND
INC
8
7
6
5
4
3
2
CVH
PDRV
IN
CVL
NDRV
PGND
PGNDC
MAX1774
32 7mm x 7mm QFN
1MDRV
24 ACO
TOP VIEW
Pin Configurations
19-1810; Rev 1; 1/02
EVALUATION KIT
AVAILABLE
Ordering Information
PART
PIN-PACKAGE
MAX1774EEI
28 QSOP
MAX1774EMJ
32 7mm x 7mm QFN
Functional Diagram
Pin Configurations continued at end of data sheet.
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.
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
AC
ADAPTER
MAIN
BATTERY
BACKUP
BATTERY
MAX1774
AC OK
LOW MAIN BATTERY
DEAD MAIN BATTERY
MAIN (+3.3V)
CORE (+1.8V)
MAX1774
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(Figure 1, VIN= V
INS
+12V, V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V, 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, MDRV, DBI, LBI, ACI,
CVH to GND.......................................................-0.3V to +30V
IN to CVH, PDRV......................................................-0.3V to +6V
BIN to CS-.................................................................-0.3V to +6V
LXB to GND................................................-0.3V to (V
BIN+ 0.7V)
PDRV to GND..................................(V
CVH
- 0.3V) to (VIN+ 0.3V)
All Other Pins to GND...............................................-0.3V to +6V
PGND to GND .......................................................-0.3V to +0.3V
Continuous Power Dissipation
28-Pin QSOP (derate 10.8mW/°C above +70°C)........860mW
32-Pin QFN (derate 23.2mW/°C above +70°C) ........1860mW
Operating Temperature.......................................-40°C to +85°C
Storage Temperature.........................................-65°C to +150°C
Temperature (soldering, 10s) ..........................................+300°C
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Input Voltage V
IN
2.7 28 V
Input Quiescent Supply Current I
IN
V
FBM
= +1.5V, V
FBC
= +1.5V,
V
SHDNM
= V
SHDNC
= +3.3V
18 40 µA
CS- Quiescent Supply Current I
CS-
V
FBM
= +1.5V, V
FBC
= +1.5V,
V
SHDNM
= V
SHDNC
= +3.3V
µA
Core Regulator Quiescent
Supply Current
I
INC
V
FBM
= +1.5V, V
FBC
= +1.5V,
V
SHDNM
= V
SHDNC
= +3.3V
60
µA
Backup Mode BIN Quiescent
Supply Current
I
BIN
V
BIN
= +3.3V, CS- open
V
FBM
= +1.5V, V
SHDNM
= +3.3V,
V
BKOFF
= +1.5V, SHDNC = GND
60
µA
IN Shutdown Supply Current SHDNM = SHDNC = GND 8 40 µA
MAIN REGULATOR
Main Output Voltage Adjust
Range
5.5 V
FBM Regulation Threshold V
FBM
V
(CS+ - CS-)
= 0 to +60mV,
V
IN
= +3.5V to +28V
V
FBM Input Current I
FBM
V
FBM
= +1.3V
0.1 µA
Current-Limit Threshold V
CS+
- V
CS-
60 80
mV
Minimum Current-Limit
Threshold
V
CS+
- V
CS-
51525mV
Valley Current Threshold V
CS+
- V
CS-
40 50 60 mV
Zero Current Threshold V
CS+
- V
CS-
0515mV
PDRV, NDRV Gate Drive
Resistance
V
CS-
= +3.3V, I
PDRV
, I
NDRV
= 50mA 2 5.5 Ω
CS- to CVL Switch Resistance I
CVL
= 50mA 4.5 9.5 Ω
PDRV, NDRV Dead Time 50 ns
110 220
1.25
1.21 1.25 1.29
-0.1
105
105
100
MAX1774
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
_______________________________________________________________________________________ 3
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Maximum Duty Cycle
%
Minimum On-Time
ns
Minimum Off-Time
ns
CORE REGULATOR
Input Voltage Range V
INC
2.6 5.5 V
V
INC
rising
INC Undervoltage Lockout
V
INC
falling
V
C or e Outp ut V ol tag e Ad j ust Rang e
1.0 5.0 V
Maximum Core Load Current V
CORE
= 1.8V (Note 1) 1 1.5 A
FBC Regulation Threshold V
FBC
V
INC
= +2.5 to +5.5V, I
O U T C
= 0 to 200mA
1.0
V
FBC Input Current I
FBC
V
FBC
= +1.3V
0.1 µA
Dropout Voltage I
OUTC
= 400mA 0.1
V
LXC Leakage Current I
LXC
V
INC
= +5.5V, V
L X C
= 0 to +5.5V -10 10 µA
LXC P-Channel, N-Channel OnResistance
0.5 Ω
LXC P-Channel Current Limit I
CLC
mA
LX C P - C hannel M i ni m um C ur r ent
mA
LXC N-Channel Valley Current
mA
LXC N-Channel Zero-Crossing
Current
40
mA
LXC Dead Time 50 ns
Max Duty Cycle
%
Minimum On-Time
ns
Minimum Off-Time
ns
BACKUP REGULATOR
Backup Battery Input Voltage
0.9 5.5 V
LXB N-Channel On-Resistance V
CS-
= +3.3V, I
LXB
= 50mA 1.9 3.5 Ω
LXB Current Limit
mA
LXB Leakage Current V
LXB
= +5.5V, V
FBM
= +1.3V 1 µA
BIN Leakage Current I
BIN
V
BIN
= +5.5V, CS- = BKOFF =
SHDNC = SHDNM = GND
1 µA
BIN, CS- Switch Resistance
V
CS-
= +3.3V, BKOFF = GND,
SHDNM = CVL
7.5 15 Ω
BIN Switch Zero-Crossing
Threshold
V
BIN
= + 2.5V , BKOFF = SHDNC =
SHDNM = C V L
17 35 mV
LXB Maximum On-Time 2.8 5.6 9.2 µs
Zero Crossing Detector Timeout
40 µs
ELECTRICAL CHARACTERISTICS (continued)
(Figure 1, VIN= V
INS
= +12V, V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V, TA= 0°C to +85°C, unless otherwise noted. Typical values are
at T
A
= +25°C.)
V
BBATT
100
200 400 650
200 400 650
2.40 2.47 2.55
2.30 2.37 2.45
0.97
-0.1
1200 1800 3000
100 250 400
900 1400 2400
100
170 400 690
170 400 690
200 350 600
0.25
110 170
1.03
0.25
MAX1774
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
4 _______________________________________________________________________________________
PARAMETER
CONDITIONS
UNITS
REFERENCE
Reference Voltage V
REF
V
Reference Load Regulation I
REF
= 0 to 50µA 10 mV
Reference Line Regulation V
CS-
= +2.5V to +5.5V, I
REF
= 50µA 5 mV
Reference Sink Current 10 µA
CVL, CVH REGULATORS
I
CVL
= 50mA, V
CS-
= 0 2.6 2.8 3.1
CVL Output Voltage V
CVL
I
CVL
= 50mA, V
CS-
= +3.3V 3.2
V
CVL Switchover Threshold CS- rising, hysteresis = 100mV typical
V
VIN = +4V, I
CVH
= 25mA
V
IN
-
3.4
V
IN
-
2.8
CVH Output Voltage V
CVH
VIN = +12V, I
CVH
= 50mA
V
IN
-
4.2
V
IN
-
3.7
V
CVH Switchover Threshold V
IN
VIN rising, hysteresis = 350mV typ 5.5 V
V
CVL
rising
CVL Undervoltage Lockout
V
CVL
falling
V
LOW-VOLTAGE COMPARATORS
V
BKOFF
rising
Backup Regulator Shutdown
Threshold
V
BKOFF
falling
V
BKOFF Input Bias Current V
BKOFF
= +5.5V 1 µA
LBI Threshold V
LBI
V
LBI
falling, hysteresis = 50mV typical
V
DBI Threshold V
DBI
V
DBI
falling, hysteresis = 50mV typical
V
BKUP Low-Input Threshold 0.4 V
LBI, DBI Input Leakage Current V
LBI
= V
DBI
= +1.3V
nA
LBO, BKUP, ACO, MDRV
Output Low
I
SINK
= 1mA 0.4 V
LBO, BKUP, ACO, MDRV
Output Leakage Current
V
LBI
= +1.3V, V
ACI
= +12V, V
ACO
=
V
LBO
= V
BKUP
= +5.5V, V
MDRV
= +28V
1.0 µA
ACI Threshold V
ACI
– V
INS,
ACI falling
V
ACI Input Leakage Current V
ACI
= +1.3V
nA
INS Input Leakage Current V
INS
= +3.3V 1.5 10 µA
LOGIC INPUTS
SHDNM, SHDNC Input Low
Voltage
0.4 V
SHDNM, SHDNC Input High
Voltage
2.0 V
ELECTRICAL CHARACTERISTICS (continued)
(Figure 1, VIN= V
INS
= +12V, V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V, TA= 0°C to +85°C, unless otherwise noted. Typical values are
at T
A
= +25°C.)
SYMBOL
MIN TYP MAX
1.23 1.25 1.27
2.40 2.47 2.55
2.40 2.47 2.55
V
BKOFF
2.30 2.37 2.45
0.51 0.55 0.59
0.46 0.50 0.54
1.17 1.20 1.23
1.17 1.20 1.23
0.22 0.35
100
100
MAX1774
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
_______________________________________________________________________________________ 5
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SHDNM, SHDNC Input Low
Current
SHDNM = SHDNC = GND -1 1 µA
SHDNC Input High Current V
SHDNC
= +5.5V 5 µA
SHDNM Input High Current V
SHDNM
= +5V 2 25 µA
ELECTRICAL CHARACTERISTICS
(Figure 1, VIN= V
INS
= +12V, V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
Input Voltage V
IN
2.7 28 V
Input Quiescent Supply Current I
IN
V
FBM
= +1.5V, V
FBC
= +1.5V, V
SHDNM
=
V
SHDNC
= +3.3V
40 µA
CS- Quiescent Supply Current I
CS-
V
FBM
= +1.5V, V
FBC
= +1.5V, V
SHDNM
=
V
SHDNC
= +3.3V
µA
Core Regulator Quiescent
Supply Current
I
INC
V
FBM
= +1.5V, V
FBC
= +1.5V, V
SHDNM
=
V
SHDNC
= +3.3V
µA
Backup Mode BIN Quiescent
Supply Current
I
BIN
V
BIN
= +3.3V, CS- open
V
FBM
= +1.5V, V
SHDNM
= +3.3V,
V
BKOFF
= +1.5V, SHDNC = GND
µA
IN Shutdown Supply Current SHDNM = SHDNC = GND 40 µA
MAIN REGULATOR
Main Output Voltage Adjust
Range
5.5 V
FBM Regulation Threshold V
FBM
V
(CS+ - CS-)
= 0 to +60mV,
V
IN
= +3.5V to +28V
V
FBM Input Current I
FBM
V
FBM
= +1.3V
0.1 µA
Current-Limit Threshold V
CS+
- V
CS-
60
mV
Minimum Current-Limit
Threshold
V
CS+
- V
CS-
525mV
Valley Current Threshold V
CS+
- V
CS-
40 60 mV
Zero Current Threshold V
CS+
- V
CS-
015mV
PDRV, NDRV Gate Drive
Resistance
V
CS-
= +3.3V, I
PDRV
, I
NDRV
= 50mA 5.5 Ω
CS- to CVL Switch Resistance I
CVL
= 50mA 9.5 Ω
Maximum Duty Cycle
%
Minimum On-Time
ns
Minimum Off-Time
ns
ELECTRICAL CHARACTERISTICS (continued)
(Figure 1, VIN= V
INS
= +12V, V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V, TA= 0°C to +85°C, unless otherwise noted. Typical values are
at T
A
= +25°C.)
1.25
1.21 1.29
-0.1
100
200 650
200 650
220
105
110
100
MAX1774
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
6 _______________________________________________________________________________________
PARAMETER
CONDITIONS
UNITS
CORE REGULATOR
Input Voltage Range V
INC
2.6 5.5 V
V
INC
rising
INC Undervoltage Lockout
V
INC
falling
V
Core Output Voltage Adjust
Range
1.0 5.0 V
Maximum Core Load Current V
CORE
= 1.8V (Note 1) 1 A
FBC Regulation Threshold V
FBC
V
INC
= +2.5 to +5.5V,
I
OUTC
= 0 to 200mA
V
FBC Input Current I
FBC
V
FBC
= +1.3V
0.1 µA
Dropout Voltage I
OUTC
= 400mA
V
LXC Leakage Current I
LXC
V
INC
= +5.5V, V
LXC
= 0 to +5.5V -10 10 µA
LXC P-Channel, N-Channel
On-Resistance
0.5 Ω
LXC P-Channel Current Limit
mA
LXC P-Channel Minimum
Current
mA
LXC N-Channel Valley Current
mA
LXC N-Channel Zero-Crossing
Current
40
mA
Max Duty Cycle
%
Minimum On-Time
ns
Minimum Off-Time
ns
BACKUP REGULATOR
Backup Battery Input Voltage
0.9 5.5 V
LXB N-Channel On Resistance V
CS-
= +3.3V, I
LXB
= 50mA 3.5 Ω
LXB Current Limit
mA
LXB Leakage Current V
LXB
= +5.5V, V
FBM
= +1.3V 1 µA
BIN Leakage Current I
BIN
V
BIN
= +5.5V, CS- = BKOFF =
SHDNC = SHDNM = GND
1µA
BIN, CS- Switch Resistance
V
CS-
= +3.3V, BKOFF = GND,
SHDNC = CVL
15 Ω
BIN Switch Zero-Crossing
Threshold
V
BIN
= +2.5V, BKOFF = SHDNC =
SHDNM = CVL
35 mV
LXB Maximum On-Time 2.8 9.2 µs
REFERENCE
Reference Voltage V
REF
V
Reference Load Regulation I
REF
= 0 to 50µA 10 mV
Reference Line Regulation V
CS-
= +2.5V to +5.5V, I
REF
= 50µA 5 mV
Reference Sink Current 10 µA
ELECTRICAL CHARACTERISTICS (continued)
(Figure 1, VIN= V
INS
= +12V, V
INC
= V
CS+
= V
CS-
= +3.3V, V
CORE
= +1.8V, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
SYMBOL
MIN MAX
2.39 2.55
2.29 2.45
V
BBATT
0.97 1.03
-0.1
1200 3010
100 420
880 2450
100
160 700
170 690
200 600
1.220 1.275
0.25
170
MAX1774
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
_______________________________________________________________________________________ 7
PARAMETER
CONDITIONS
UNITS
CVL, CVH REGULATORS
CVL Output Voltage V
CVL
I
CVL
= 50mA, V
CS-
= 0 2.6 3.1 V
CVL Switchover Threshold V
CS-
rising, hysteresis = 100mV typical
V
VIN = +4V, I
CVH
= 25mA
CVH Output Voltage V
CVH
VIN = +12V, I
CVH
= 50mA
V
V
CVL
rising
CVL Undervoltage Lockout
V
CVL
falling
V
LOW-VOLTAGE COMPARATORS
V
BKOFF
rising
Backup Regulator Shutdown
Threshold
V
BKOFF
falling
V
BKOFF Input Bias Current V
BKOFF
= +5.5V 1 µA
LBI Threshold V
LBI
V
LBI
falling, hysteresis = 50mV typical
V
DBI Threshold V
DBI
V
DBI
falling, hysteresis = 50mV typical
V
BKUP Low-Input Threshold 0.4 V
LBI, DBI Input Leakage Current V
LBI
, V
DBI
= +28V
nA
LBO, BKUP, ACO, MDRV
Output Low
I
SINK
= 1mA 0.4 V
LBO, BKUP, ACO, MDRV
Output Leakage Current
V
LBI
= +1.3V, V
ACI
= VIN = +12V, V
ACO
=
V
LBO
= V
BKUP
= +5.5V, V
MDRV
= +28V
1.0 µA
ACI Threshold V
ACI
- V
INS
, ACI falling 0.5 V
ACI Input Leakage Current V
ACI
= +1.3V
nA
MAIN Input Leakage Current V
INS
= +3.3V 10 µA
LOGIC INPUTS
SHDNM, SHDNC Input Low
Voltage
0.4 V
SHDNM, SHDNC Input High
Voltage
2.0 V
SHDNM, SHDNC Input Low
Current
SHDNM = SHDNC = GND -1 1 µA
SHDNC Input High Current V
SHDNC
= +5.5V 5 µA
SHDNM Input High Current V
SHDNM
= +28V 25 µA
ELECTRICAL CHARACTERISTICS (continued)
(Figure 1, VIN= V
INS
= +12V, V
INC
= V
CS+
= V
CS-
= +3.3V, V
CORE
= +1.8V, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
Note 1: This parameter is guaranteed based on the LXC P-channel current limit and the LXC N-channel valley current.
Note 2: Specifications to -40°C are guaranteed by design and not production tested.
SYMBOL
V
BKOFF
MIN MAX
2.40 2.55
VIN - 2.8
VIN - 3.65
2.40 2.57
2.30 2.47
0.51 0.59
0.46 0.54
1.17 1.23
1.17 1.23
100
100
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