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IT
TION K
VALUA
E
BLE
AVAILA
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
General Description
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
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 detec-
tors 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 P-
channel MOSFET switches input to the main battery.
When the main battery is low, the backup step-up con-
verter sustains the main output voltage. When the back-
up battery can no longer deliver the required load, the
system shuts down safely to prevent damage. Four on-
board 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
Pin Configurations
BKUP
N.C.
LXC
LBO
INS
N.C.
Ordering Information
PART
MAX1774EEI
MAX1774EGJ
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 QSOP
32 7mm x 7mm QFN
TOP VIEW
GND
SHDNC
SHDNM
32
31
30
29
28
27
26
25
GND
MDRV
PGNDC
PGND
NDRV
CVL
IN
PDRV
CVH
1
2
3
4
5
6
7
8
10
11
12
13
14
15
16
24
23
22
21
ACO
INC
GND
FBC
CS-
CS+
FBM
N.C.
BACKUP
BATTERY
MAIN
BATTERY
AC
ADAPTER
Functional Diagram
MAIN (+3.3V)
MAX1774
20
19
18
17
MAX1774
CORE (+1.8V)
AC OK
LOW MAIN BATTERY
DEAD MAIN BATTERY
GND
GND
9
LXB
BKOFF
LXB2
REF
BIN
DBI
ACI
LBI
32 7mm x 7mm QFN
Pin Configurations continued at end of data sheet.
1
________________________________________________________________
Maxim Integrated Products
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.
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
MAX1774
ABSOLUTE MAXIMUM RATINGS
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 (V
IN
+ 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 Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Temperature (soldering, 10s) ..........................................+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
(Figure 1, V
IN
= V
INS
+12V, V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at
T
A
= +25°C.)
PARAMETER
Input Voltage
Input Quiescent Supply Current
CS- Quiescent Supply Current
Core Regulator Quiescent
Supply Current
Backup Mode BIN Quiescent
Supply Current
IN Shutdown Supply Current
MAIN REGULATOR
Main Output Voltage Adjust
Range
FBM Regulation Threshold
FBM Input Current
Current-Limit Threshold
Minimum Current-Limit
Threshold
Valley Current Threshold
Zero Current Threshold
PDRV, NDRV Gate Drive
Resistance
CS- to CVL Switch Resistance
PDRV, NDRV Dead Time
V
FBM
I
FBM
V
(CS+ - CS-)
= 0 to +60mV,
V
IN
= +3.5V to +28V
V
FBM
= +1.3V
V
CS+
- V
CS-
V
CS+
- V
CS-
V
CS+
- V
CS-
V
CS+
- V
CS-
V
CS-
= +3.3V, I
PDRV
, I
NDRV
= 50mA
I
CVL
= 50mA
1.25
1.21
-0.1
60
5
40
0
80
15
50
5
2
4.5
50
1.25
5.5
1.29
0.1
100
25
60
15
5.5
9.5
V
V
µA
mV
mV
mV
mV
Ω
Ω
ns
SYMBOL
V
IN
I
IN
I
CS-
I
INC
V
FBM
= +1.5V, V
FBC
= +1.5V,
V
SHDNM
= V
SHDNC
= +3.3V
V
FBM
= +1.5V, V
FBC
= +1.5V,
V
SHDNM
= V
SHDNC
= +3.3V
V
FBM
= +1.5V, V
FBC
= +1.5V,
V
SHDNM
= V
SHDNC
= +3.3V
V
BIN
= +3.3V, CS- open
V
FBM
= +1.5V, V
SHDNM
= +3.3V,
V
BKOFF
= +1.5V,
SHDNC
= GND
SHDNM
=
SHDNC
= GND
CONDITIONS
MIN
2.7
18
110
60
TYP
MAX
28
40
220
105
UNITS
V
µA
µA
µA
I
BIN
60
8
105
40
µA
µA
2
_______________________________________________________________________________________
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
ELECTRICAL CHARACTERISTICS (continued)
(Figure 1, V
IN
= V
INS
= +12V, V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are
at T
A
= +25°C.)
PARAMETER
Maximum Duty Cycle
Minimum On-Time
Minimum Off-Time
CORE REGULATOR
Input Voltage Range
INC Undervoltage Lockout
Core Output Voltage Adjust Range
Maximum Core Load Current
FBC Regulation Threshold
FBC Input Current
Dropout Voltage
LXC Leakage Current
LXC P-Channel, N-Channel On-
Resistance
LXC P-Channel Current Limit
LXC P-Channel Minimum Current
LXC N-Channel Valley Current
LXC N-Channel Zero-Crossing
Current
LXC Dead Time
Max Duty Cycle
Minimum On-Time
Minimum Off-Time
BACKUP REGULATOR
Backup Battery Input Voltage
LXB N-Channel On-Resistance
LXB Current Limit
LXB Leakage Current
BIN Leakage Current
BIN, CS- Switch Resistance
BIN Switch Zero-Crossing
Threshold
LXB Maximum On-Time
Zero Crossing Detector Timeout
I
BIN
V
LXB
= +5.5V, V
FBM
= +1.3V
V
BIN
= +5.5V, CS- =
BKOFF
=
SHDNC
=
SHDNM
= GND
V
CS-
= +3.3V,
BKOFF
= GND,
SHDNM
= CVL
V
BIN
= +2.5V,
BKOFF
=
SHDNC
=
SHDNM
= CVL
2.8
7.5
17
5.6
40
V
BBATT
V
CS-
= +3.3V, I
LXB
= 50mA
200
0.9
1.9
350
5.5
3.5
600
1
1
15
35
9.2
V
Ω
mA
µA
µA
Ω
mV
µs
µs
100
170
170
400
400
690
690
I
CLC
1200
100
900
40
I
LXC
V
FBC
I
FBC
V
CORE
= 1.8V (Note 1)
V
INC
= +2.5 to +5.5V, I
O U T C
= 0 to 200mA
V
FBC
= +1.3V
I
OUTC
= 400mA
V
INC
= +5.5V, V
L X C
= 0 to +5.5V
-10
0.25
1800
250
1400
110
50
V
INC
V
INC
rising
V
INC
falling
2.6
2.40
2.30
1.0
1
0.97
-0.1
0.1
1.5
1.0
1.03
0.1
0.25
10
0.5
3000
400
2400
170
2.47
2.37
5.5
2.55
2.45
5.0
V
V
V
A
V
µA
V
µA
Ω
mA
mA
mA
mA
ns
%
ns
ns
SYMBOL
CONDITIONS
MIN
100
200
200
400
400
650
650
TYP
MAX
UNITS
%
ns
ns
MAX1774
_______________________________________________________________________________________
3
Dual, High-Efficiency, Step-Down
Converter with Backup Battery Switchover
MAX1774
ELECTRICAL CHARACTERISTICS (continued)
(Figure 1, V
IN
= V
INS
= +12V, V
INC
= V
CS-
= V
CS+
= +3.3V, V
CORE
= +1.8V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are
at T
A
= +25°C.)
PARAMETER
REFERENCE
Reference Voltage
Reference Load Regulation
Reference Line Regulation
Reference Sink Current
CVL, CVH REGULATORS
CVL Output Voltage
CVL Switchover Threshold
V
CVL
I
CVL
= 50mA, V
CS-
= 0
I
CVL
= 50mA, V
CS-
= +3.3V
CS- rising, hysteresis = 100mV typical
V
IN
= +4V, I
CVH
= 25mA
CVH Output Voltage
V
CVH
V
IN
= +12V, I
CVH
= 50mA
CVH Switchover Threshold
CVL Undervoltage Lockout
LOW-VOLTAGE COMPARATORS
Backup Regulator Shutdown
Threshold
BKOFF
Input Bias Current
LBI Threshold
DBI Threshold
BKUP
Low-Input Threshold
LBI, DBI Input Leakage Current
LBO, BKUP, ACO, MDRV
Output Low
LBO, BKUP, ACO, MDRV
Output Leakage Current
ACI Threshold
ACI Input Leakage Current
INS Input Leakage Current
LOGIC INPUTS
SHDNM, SHDNC
Input Low
Voltage
SHDNM, SHDNC
Input High
Voltage
2.0
0.4
V
V
V
LBI
= V
DBI
= +1.3V
I
SINK
= 1mA
V
LBI
= +1.3V, V
ACI
= +12V, V
ACO
=
V
LBO
= V
BKUP
= +5.5V, V
MDRV
= +28V
V
ACI
– V
INS,
ACI falling
V
ACI
= +1.3V
V
INS
= +3.3V
1.5
0.22
V
LBI
V
DBI
V
BKOFF
V
BKOFF
rising
V
BKOFF
falling
V
BKOFF
= +5.5V
V
LBI
falling, hysteresis = 50mV typical
V
DBI
falling, hysteresis = 50mV typical
1.17
1.17
0.4
100
0.4
1.0
0.35
100
10
1.20
1.20
0.51
0.46
0.55
0.50
0.59
0.54
1
1.23
1.23
V
µA
V
V
V
nA
V
µA
V
nA
µA
V
IN
V
IN
rising, hysteresis = 350mV typ
V
CVL
rising
V
CVL
falling
2.40
2.30
2.40
2.6
2.8
3.2
2.47
V
IN
-
3.4
V
IN
-
4.2
5.5
2.47
2.37
2.55
2.45
2.55
V
IN
-
2.8
V
V
IN
-
3.7
V
V
3.1
V
V
V
REF
I
REF
= 0 to 50µA
V
CS-
= +2.5V to +5.5V, I
REF
= 50µA
10
1.23
1.25
1.27
10
5
V
mV
mV
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
4
_______________________________________________________________________________________
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