Maxim MAX797HESE Datasheet
_______________General Description
The MAX797H high-performance, step-down DC-DC
converter provides main CPU power in battery-powered
systems. A 40V rating on the power stage’s input allows
operation with high-cell-count batteries and a wide
range of AC adaptors. This buck controller achieves
96% efficiency by using synchronous rectification and
Maxim’s proprietary Idle Mode™ control scheme to
extend battery life at full-load (up to 10A) and no-load
outputs. Excellent dynamic response corrects output transients caused by the latest dynamic-clock CPUs within five
300kHz clock cycles. Unique bootstrap circuitry drives
inexpensive N-channel MOSFETs, reducing system cost
and eliminating the crowbar switching currents found in
some PMOS/NMOS switch designs.
The MAX797H has a logic-controlled and synchronizable
fixed-frequency, pulse-width-modulating (PWM) operating
mode, which reduces noise and RF interference in sensitive mobile-communications and pen-entry applications.
The SKIP override input allows automatic switchover to
idle-mode operation (for high-efficiency pulse skipping) at
light loads, or forces fixed-frequency mode for lowest noise
at all loads. The MAX797H is pin compatible with the popular MAX797, but has a higher input voltage range.
The MAX797H comes in a 16-pin narrow SO package.
________________________Applications
Notebook and Subnotebook Computers
Industrial Controls
____________________________Features
♦ 96% Efficiency
♦ Up to 40V Power Input
♦ 2.5V to 6V Adjustable Output
♦ Preset 3.3V and 5V Outputs (at up to 10A)
♦ 5V Linear-Regulator Output
♦ Precision 2.505V Reference Output
♦ Automatic Bootstrap Circuit
♦ 150kHz/300kHz Fixed-Frequency PWM Operation
♦ Programmable Soft-Start
♦ 375µA Quiescent Current (VIN= 12V, V
OUT
= 5V)
♦ 1µA Shutdown Current
MAX797H
High-Voltage, Step-Down Controller with
Synchronous Rectifier for CPU Power
________________________________________________________________
Maxim Integrated Products
1
Idle Mode is a trademark of Maxim Integrated Products.
19-1239; Rev 0; 7/97
__________________Pin Configuration
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
DH
LX
BST
DLGND
REF
SKIP
SS
TOP VIEW
MAX797H
PGND
VL
V+
CSL
CSH
FB
SHDN
SYNC
SO
__________Typical Operating Circuit
MAX797H
SHDN
DH
+3.3V
OUTPUT
+4V TO +40V
POWER INPUT
BST
LX
DL
PGND
CSH
CSL
SS
REF
SYNC
GND
SKIP FB
V+
+4.5V TO +30V
SUPPLY
INPUT
VL
PIN-PACKAGETEMP. RANGEPART
†
16 Narrow SO-40°C to +85°CMAX797HESE
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
For small orders, phone 408-737-7600 ext. 3468.
______________Ordering Information
†
U.S. and foreign patents pending.
MAX797H
High-Voltage, Step-Down Controller with
Synchronous Rectifier for CPU Power
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V+ = 15V, GND = PGND = 0V, IVL= I
REF
= 0A, TA= 0°C to +85°C, SYNC = 0V, 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.
V+ to GND ................................................................-0.3V to 36V
GND to PGND........................................................................±2V
VL to GND...................................................................-0.3V to 7V
BST to GND ..............................................................-0.3V to 46V
DH to LX.....................................................-0.3V to (BST + 0.3V)
LX to BST....................................................................-7V to 0.3V
SHDN to GND...........................................................-0.3V to 36V
SYNC, SS, REF, FB, SKIP, DL to GND...........-0.3V to (VL + 0.3V)
CSH, CSL to GND.......................................................-0.3V to 7V
VL Short Circuit to GND..............................................Momentary
REF Short Circuit to GND...........................................Continuous
VL Output Current...............................................................50mA
Continuous Power Dissipation (T
A
= +70°C)
SO (derate 8.70mW/°C above +70°C)........................696mW
Operating Temperature Range
MAX797HESE.................................................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
Rising edge, hysteresis = 25mV
V+
Rising edge, hysteresis = 15mV
SHDN = 2V, 0mA < IVL< 25mA, 5.5V < V+ < 30V
CSH - CSL, negative
CSH - CSL, positive
FB = VL, 6V < power input < 40V (Note 4)
25mV < (CSH - CSL) < 80mV
0mV < (CSH - CSL) < 80mV, FB = VL,
6V < power input < 40V, includes line and load
regulation (Note 4)
External resistor divider
CSH - CSL = 0V
0mV < (CSH - CSL) < 80mV
CONDITIONS
V4.2 4.7VL/CSL Switchover Voltage
V3.8 4.1VL Fault Lockout Voltage
V4.7 5.3VL Output Voltage
mA2.0SS Fault Sink Current
µA2.5 4.0 6.5SS Source Current
40
V
4.5 30
Input Supply Range
-50 -100 -160
mV
80 100 120
Current-Limit Voltage
1.5
V4.85 5.10 5.255V Output Voltage (CSL)
VREF 6
Nominal Adjustable Output
Voltage Range
V2.43 2.505 2.57Feedback Voltage
%
2.5
Load Regulation
UNITSMIN TYP MAXPARAMETER
High-side MOSFET drain
0mV < (CSH - CSL) < 80mV, FB = 0V,
4.5V < power input < 40V, includes line and load
regulation (Note 4)
V3.20 3.35 3.463.3V Output Voltage (CSL)
FB = 0V, 4.5V < power input < 40V (Note 4)
%/V
0.04 0.06
Line Regulation
+3.3V AND +5V STEP-DOWN CONTROLLERS
FLYBACK/PWM CONTROLLERINTERNAL REGULATOR AND REFERENCE
0.04 0.06
MAX797H
High-Voltage, Step-Down Controller with
Synchronous Rectifier for CPU Power
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, GND = PGND = 0V, IVL= I
REF
= 0A, TA= 0°C to +85°C, SYNC = 0V, unless otherwise noted.)
SHDN, 0V or 30V
SHDN, SKIP
SYNC
SYNC = 0V or 5V
No external load (Note 1)
SYNC = REF
Guaranteed by design
CSH = CSL = 6V
V+ = 4V, CSL = 0V (Note 2)
SYNC = 0V or 5V
SHDN = 0V, V+ = 30V, CSL = 0V or 6V
Falling edge
0µA < I
REF
< 100µA
SYNC = REF
SHDN = 0V, CSL = 6V, V+ = 0V or 30V, VL = 0V
CONDITIONS
2.0
2.0
V
VL - 0.5
Input High Voltage
%
93 96
89 91
Maximum Duty Factor
kHz190 340Oscillator Sync Range
ns200SYNC Rise/Fall Time
ns200SYNC Low Pulse Width
ns200SYNC High Pulse Width
125 150 175
kHz
270 300 330
Oscillator Frequency
2.45 2.505 2.55 VReference Output Voltage
mW4.8 6.6Quiescent Power Consumption
mW4 8Dropout Power Consumption
1 5 µAV+ Shutdown Current
V1.8 2.3Reference Fault Lockout Voltage
mV50Reference Load Regulation
µA0.1 1CSL Shutdown Leakage Current
UNITSMIN TYP MAXPARAMETER
FB = CSH = CSL = 6V, VL switched over to CSL 1 5 µAV+ Off-State Leakage Current
DL forced to 2V
FB, FB = REF
CSH, CSL, CSH = CSL = 4V, device not shut down
SYNC, SKIP
A1DL Sink/Source Current
±100
50
1.0
SHDN, SKIP
SYNC
0.5
V
0.8
Input Low Voltage
DH forced to 2V, BST - LX = 4.5V A1DH Sink/Source Current
High or low, BST - LX = 4.5V
High or low
Ω7DH On-Resistance
Ω7DL On-Resistance
OSCILLATOR AND INPUTS/OUTPUTS
nA
Input Current
µA
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