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Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
General Description
The MAX16984 combines a 5V automotive-grade stepdown converter capable of driving up to 2.5A, a USB host
charger adapter emulator, and USB protection switches
for automotive USB host applications. The USB protection
switches provide high-ESD, short-circuit protection and
feature integrated host-charger port-detection circuitry
adhering to the USB 2.0 Battery Charging Specification BC1.2 battery charging specification and Chinese
Telecommunication Industry Standard YD/T 1591-2009.
They also include circuitry for iPod®/iPhone® 1.0A and
iPad® 2.1A dedicated charging modes. The HVD+ and
HVD- ESD protection features include protection to ±15kV
Air/±8kV Contact on the HVD+ and HVD- outputs to the
IEC 61000-4-2 model and 330Ω, 330pF ESD model.
The high-efficiency step-down DC-DC converter
operates from a voltage up to 28V and is protected
from load dump transients up to 42V. The device is optimized for high-frequency operation and includes resistorprogrammable frequency selection from 220kHz to 2.2MHz
to allow optimization of efficiency, noise, and board space
based on application requirements. The converter has
an internal high-side n-channel switch and uses a low
forward-drop freewheeling Schottky diode for rectification.
There is a small low-side n-channel switch to maintain fixed
frequency under light loads. For lower quiescent current
operation requirements, the low side n-channel switch can
be disabled to allow skip mode operation under light loads.
The converter can deliver up to 2.1A of continuous current
at 105°C. The MAX16984S has an integrated spreadspectrum oscillator to improve EMI performance.
The MAX16984 also includes a USB load current-sense
amplifier and configurable feedback adjustment circuit
designed to provide automatic USB voltage adjustment to
compensate for voltage drops in captive cables associated
with automotive applications. The MAX16984 limits the
USB load current using both a fixed internal peak current
threshold of the DC-DC converter and a user-configurable
external USB load current-sense amplifier threshold.
Applications
●
●
●
●
●
Automotive Radio and Navigation
USB Port for Host and Hub Applications
Automotive Connectivity
Telematics
Dedicated USB Power Charger
MAX16984
Benefits and Features
● Integrated DC-DC and USB Host Charge Emulator
Enables 1-Chip Solution Directly from Car Battery to
Portable Device
• 4.5V to 28V (42V Load Dump) Operating Voltage
• 5V, 2.5A Output Current Capability
• Low-Q Current Skip and Shutdown Modes
• Soft-Start Reduces Inrush Current
● Low-Noise Features Prevent Interference with AM
Band and Portable Devices
• Fixed-Frequency 220kHz to 2.2MHz Operation
• Forced-PWM Option at No Load
• Spread Spectrum for EMI Reduction
• SYNC Input for Frequency Parking
● Optimal USB Power and Communication for
Portable Devices
• User-Adjustable Voltage Gain Adjusts Output
Between 5V and 6.15V for Cable Compensation
• ±3% Accuracy User-Adjustable USB Current Limit
• 4Ω USB 2.0 480Mbps/12Mbps Data Switches
• Integrated iPod/iPhone/iPad Charge-Detection
Termination Resistors
• Supports USB BC1.2 Charging Downstream Port
(CDP) and Dedicated Charging Port (DCP) Modes
• Supports Chinese Telecommunication Industry
Standard YD/T 1591-2009
• Compatible with USB On-the-Go Specification
• High-Speed Pass-Through Mode
● Robust Design Keeps Vehicle System and
Portable Devices Safe in Automotive Environment
• Short-to-Battery Protection on DC-DC Converter
• Short-to-Battery Protection on USB Pins
• ±25kV Air/±8kV Contact ISO 10605
• ±15kV Air/±8kV Contact IEC 61000-4-2
• ±15kV Air/±8kV Contact (330Ω, 330pF)
• Fault-Indication Active-Low, Open-Drain Output
• Reduced Inrush Current with Soft-Start
• Overtemperature Protection
• -40°C to +125°C Operating Temperature Range
• 28-Pin, 5mm x 5mm, TQFN and Side-Wettable
QFND Packages
• 4mm x 4mm, 28-Pin CPQFN and Side-Wettable
version available
Ordering Information and Typical Operating Circuit appear at
end of data sheet.
iPod, iPhone, and iPad are registered trademarks of Apple, Inc.
19-6627; Rev 8; 3/21
© 2021 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners.
One Analog Way, Wilmington, MA 01887 U.S.A.
|
Tel: 781.329.4700
|
© 2021 Analog Devices, Inc. All rights reserved.
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Absolute Maximum Ratings
BST to LX (Note 1)...................................................-0.3V to +6V
PGND to GND.......................................................-0.3V to +0.3V
Output Short-Circuit Duration.....................................Continuous
Continuous Power Dissipation (TA = 70°C)
Side-Wettable QFND (derate 33.3mW/°C above +70°C)...2666.7mW
TQFN (derate 34.5mW/°C above +70°C) .................2759mW
Operating Temperature Range...........................-40°C to +125°C
Junction Temperature...................................................... +150°C
Storage Temperature Range..............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
IN, D+, D-, CD0, CD1, FBPER,
FBMAX, SENSO, FBCAP to GND.......................-0.3V to +6V
FAULT, FOSC, BIAS, SYNC to GND.......................-0.3V to +6V
D+, D-, to IN........................................................................+0.3V
HVD+, HVD- to GND..............................................-0.3V to +18V
SENSN, SENSP to GND........................................-0.3V to +30V
SENSP to SENSN.................................................-6.0V to +6.0V
SUP, SUPSW, ENBUCK to GND...........................-0.3V to +42V
LX (Note 1).............................................................-0.3V to +42V
SUP to SUPSW.....................................................-0.3V to +0.3V
BST to GND...........................................................-0.3V to +47V
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.
Package Thermal Characteristics (Note 2)
Side-Wettable QFND
Junction-to-Ambient Thermal Resistance (qJA)...........30°C/W
Junction-to-Case Thermal Resistance (qJC)..................2°C/W
TQFN
Junction-to-Ambient Thermal Resistance (qJA)...........29°C/W
Junction-to-Case Thermal Resistance (qJC)..................2°C/W
CPQFN
Junction-to-Ambient Thermal Resistance (qJA)...........35°C/W
Junction-to-Case Thermal Resistance (qJC)..................3°C/W
Note 1: Self-protected against transient voltages exceeding these limits for ≤ 50ns under normal operation and loads up to the
maximum rated output current.
Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Electrical Characteristics
(VSUP = VSUPSW = 14V, VENBUCK = VIN = 3.3V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
(Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
28
V
42
V
6
20
µA
620
950
µA
POWER SUPPLY AND ENABLE
Supply Voltage Range
Load Dump Event Supply
Voltage Range
VSUP
VSUP_LD
Normal operation
4.5
t < 1s (Note 4)
VIN = 0V
Supply Current
BIAS Voltage
ISUP
VBIAS
VSYNC = 0V, no load, skip mode
VSYNC = 3.3V, no load, FPWM mode
(Note 4)
5.75V < VSUP = VSUPSW < 28V
4.71
5
40
120
VBIAS rising
3.93
4.2
BIAS Current Limit
BIAS Undervoltage Lockout
VUV_BIAS
9
BIAS Undervoltage Lockout
Hysteresis
3.0
IN Enable High
VIN_IH
1.6
IN Enable Low
VIN_IL
www.analog.com
5.31
V
mA
4.46
0.36
VIN
IN Voltage Range
mA
V
V
3.6
V
V
0.5
V
Analog Devices │ 2
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Electrical Characteristics (continued)
(VSUP = VSUPSW = 14V, VENBUCK = VIN = 3.3V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
(Note 3)
PARAMETER
SYMBOL
IN Overvoltage Lockout
VIN_OVLO
IN Input Current
CONDITIONS
VIN rising
MIN
TYP
MAX
UNITS
3.85
4.0
4.15
V
5
10
µA
IIN
ENBUCK Enable High
VENBUCK_IH
ENBUCK Enable Low
VENBUCK_IL
2.4
ENBUCK Hysteresis
V
0.6
V
1
µA
3.6
V
4.15
V
0.15
ENBUCK Input Leakage
VENBUCK = 42V
0.01
V
D+, D- ANALOG USB SWITCHES
Guaranteed by RON measurement
(Note 4)
Analog Signal Range
Protection Trip Threshold
VOV_D
Protection Response Time
tFP_D
0
3.7
3.85
VIN = 4.0V, VHVD± = 3.3V to 4.3V step,
RL = 15kΩ on D±, delay to VD± < 3V
5
µs
Overvoltage Blanking Timeout
Period
tB,OV_D
From overvoltage condition to FAULT
asserted
18
On-Resistance Switch A
RON_SA
IL = 5mA, 0V < V D± < 3.6V
4
IL = 5mA, VD_= 1.5V or 3.0V
10
IL = 5mA,VD_ = 0V or 0.4V
10
VDP = 1V, IDM = 500µA
90
180
0
+0.1
On-Resistance Match Between
Channels Switch A
On-Resistance Flatness Switch A
DRON_SA
RFLAT(ON)A
On-Resistance of HVD+/HVDShort
RSHORT
HVD+/HVD- On-Leakage Current
IHVD_ON
HVD+/HVD- Off-Leakage Current
IHVD_OFF
D+/D- Off-Leakage Current
ID_OFF
VHVD± = 0V
-0.1
VHVD± = 3.6V
150
mΩ
mΩ
12
-1
ms
Ω
2.5
VHVD± = 18V, VD± = 0V
VHVD± = 18V, VD± = 0V
RL = 50Ω, source impedance 50Ω
(Figure 3)
30
Ω
µA
µA
+1
µA
400
MHz
RL = 50Ω, f = 480MHz (Figure 3)
-14
dB
CON
f = 240MHz, VBIAS = 250mV,
V = 500mVP-P
15
pF
Rise-Time Propagation Delay
tPLH
RS = RL = 50Ω
200
ps
Fall-Time Propagation Delay
tPHL
RS = RL = 50Ω
200
ps
Skew between D+ and D- switch,
RL = 50Ω
50
ps
50
ps
2.50
mA/V
On-Channel -3dB Bandwidth
BW
Crosstalk
VCT
On-Capacitance Switch A
Output Skew Between Switches
tSK(O)
Skew between opposite transitions in
same switch, RL = 50Ω
CURRENT-SENSE AMP (SENSP, SENSN, FBMAX, SENSO)
Output Skew Same Switch
FBMAX, SENSO
Transconductance
www.analog.com
tSK(P)
GSENSO,
GFBMAX
I/(VSENSP - VSENSN),
VSENSP = 5.25V
Analog Devices │ 3
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Electrical Characteristics (continued)
(VSUP = VSUPSW = 14V, VENBUCK = VIN = 3.3V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
(Note 3)
PARAMETER
SYMBOL
SENSO, FBMAX Voltage Range
VSENSO,
VFBMAX
Input Differential Voltage Range
ΔVSENSO,
ΔVFBMAX
CONDITIONS
VSENSP - VSENSN
MIN
MAX
UNITS
0
1.2
V
0
120
mV
Determined by external RC time constant;
assumed R = 10kΩ, and C = 10pF
Bandwidth of Transconductance
SENSP Pulldown Resistance
VSENSP = 5.05V, VENBUCK = 0V or CD1
RSENSP_DIS toggle; going into and out of auto-detection
modes
SENSP Discharge Time Upon
CD1 Toggle
tSENSP_DIS
CD1 toggle; going into and out of autodetection modes
SENSP Input Bias Current
tSENSP_LK
SENSN Input Bias Current
tSENSN_LK
TYP
1
MHz
300
600
Ω
1.1
2
s
VSENSP = 5.05V
130
230
µA
VSENSN = 5.05V
70
120
µA
SENSP Voltage Range
0.5
28
V
SENSN Overvoltage Threshold
VOV_SENSN
6.8
7
7.1
V
SENSP Undervoltage Threshold
VUV_SENSP
4.64
4.75
4.81
V
SENSN Protection Response
Time
tOV_SENSN
SENSN Overvoltage Fault
Blanking Timeout Period
3.2
tB,OV_
SENSN
8
From overvoltage condition to FAULT
asserted
3
10
µs
20
ms
SENSO CURRENT LIMIT RELATIONSHIP
SENSO ILIMIT Threshold
Continuous Current-Limit Fault
Blanking Timeout
VTH_ILIM
tB,ILIM
SENSO rising, threshold used to set DC
current limit
From overcurrent condition to FAULT
asserted
1.20
9
16.5
V
27
ms
ANALOG FEEDBACK ADJ
SENSP Analog Adjustment Gain
ΔVSENSP/ΔVFBMAX
ASENSP
VFBPER = 3.3V
0.535
V/V
VFBPER = 0V
1.069
V/V
25
%
12.5
%
1.2
V
Maximum Feedback Adjustment
(compared to SENSP)
VFBPER = 0V, VFBMAX = 1.2V
Maximum Feedback Adjustment
(compared to SENSP)
VFBPER = 3.3V, VFBMAX = 1.2V
FBMAX Maximum Adjustment
Threshold
CD0, CD1, FBPER INPUT
VPIN = 5.5V, internal 2MΩ pulldown to GND
Input Current
Logic-High
VIH
Logic-Low
VIL
www.analog.com
2.8
5.6
1.6
µA
V
0.5
V
Analog Devices │ 4
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Electrical Characteristics (continued)
(VSUP = VSUPSW = 14V, VENBUCK = VIN = 3.3V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
(Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
USB 2.0 HOST CHARGER DETECTION, D+/DInput Logic-High
Input Logic-Low
Data Sink Current
2.0
VIH
V
VIL
IDAT_SINK
Data Detect Voltage High
VDAT_REFH
Data Detect Voltage Low
VDAT_REFL
Data Detect Voltage Hysteresis
VDAT_HYST
Data Source Voltage
VDAT_SRC
Data Source Load Current
IDAT_SRC
VDAT_SINK = 0.25V to 0.4V
50
100
0.8
V
160
µA
0.4
V
0.25
55
0.5
V
mV
0.7
V
200
µA
iPhone/iPad/DCP CHARGER DETECTION
HVD+/HVD- Short Pulldown
RPD
300
500
750
kΩ
RP1/RP2 Ratio
RTRP
1.485
1.5
1.515
Ratio
RM1/RM2 Ratio
RTRM
0.857
0.866
0.875
Ratio
45
46
47
29
30
31
6
7
8
45
46
47
55.9
57.2
58.5
4
9
15
iPhone mode, DM falling (in % of VBIAS)
iPad mode, DM falling (in % of VBIAS)
DM1 Comparator Threshold
VDM1F
DM2 Comparator Threshold
VDM2F
DP Comparator Threshold
VDPR
DM1 Comparator Debounce Time
tDM1
VDM1 step from 2.8V to 1.5V
DM2 Comparator Debounce Time
tDM2
VDM2 step from 2.0V to 0.2V
DP Comparator Debounce Time
tDP
DM falling (in % of VBIAS)
iPhone mode, DP rising (in % of VBIAS)
iPad mode, DP rising (in % of VBIAS)
VDP step from 1.5V to 2.5V
%
%
%
ms
1
2
4
s
600
1100
1800
µs
SYNCHRONOUS STEP-DOWN DC-DC CONVERTER
PWM Output Voltage Accuracy
VSENSP
Skip Mode Output Voltage
Accuracy
VSENSP_
SKIP
Oscillator Frequency
www.analog.com
7V < VSUPSW < 18V, no load, VSYNC =
0V, not in FPWM mode (Note 4)
5.05
4.96
7V < VSUPSW < 18V, 0A < ILOAD < 2.1A,
VFBMAX = GND (Note 4)
Load Regulation
Output Voltage Accuracy
7V < VSUPSW < 18V, no load,
VSYNC = 3.3V or VSYNC = 0V and FPWM
mode (see TOC 24)
VSENSP
fSW
5.05
V
5.25
1.2
V
%/A
VSUPSW = 16V, ILOAD = 2.1A; VFBPER
= 0V, VFBMAX = 1.2V, VSYNC = 0V and
FPWM mode (Note 4)
6
VSUPSW = 8V, ILOAD = 2.1A; VFBPER
= 0V, VFBMAX = 1.2V, VSYNC = 0V and
FPWM mode (Note 4)
6
6.15
6.3
RFOSC = 68kΩ
380
440
480
kHz
RFOSC = 12kΩ
2.0
2.2
2.4
MHz
6.15
6.3
V
Analog Devices │ 5
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Electrical Characteristics (continued)
(VSUP = VSUPSW = 14V, VENBUCK = VIN = 3.3V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.)
(Note 3)
PARAMETER
SYMBOL
Spread-Spectrum Range
CONDITIONS
MIN
MAX16984S only
SYNC Switching Threshold Hi
VSYNC_HI
Rising
SYNC Switching Threshold Lo
VSYNC_LO
Falling
TYP
MAX
6.5
%
1.4
SYNC Internal Pulldown
UNITS
V
200
0.4
V
550
kΩ
SYNC Input Clock Acquisition
Time
tSYNC
(Note 4)
1
High-Side Switch On Resistance
RONH
ILX = 1A
200
450
mI
Low-Side Switch On Resistance
RONL
ILX = 500mA
1
2
Ω
BST Input Current
IBST
1.2
2
mA
3.6
4.7
A
LX Current-Limit Threshold
Skip Mode Peak Current
Threshold
VBST - VLX = 5V, high side on
Peak Inductor current
ISKIP_TH
300
Negative Current Limit
Soft-Start Ramp Time
2.7
Cycle
0.65
tSS
0.85
mA
1.1
9
A
ms
FAULT OUTPUT
Output-High Leakage Current
VFAULT = 5.5V
Output Low Level
Sinking 1mA
-5
0.03
+5
µA
0.4
V
THERMAL OVERLOAD
Thermal Shutdown Temperature
+174
°C
30
°C
Human Body Model
±2
kV
ISO 10605 Air Gap
±25
kV
ISO 10605 Contact
±8
kV
IEC 61000-4-2 Air Gap
±15
kV
IEC 61000-4-2 Contact
±8
kV
330I, 330pF Air Gap
±15
kV
330I, 330pF Contact
±8
kV
Thermal Shutdown Hysteresis
ESD PROTECTION (ALL PINS)
ESD Protection Level
VESD
ESD PROTECTION (HVD+, HVD-)
ESD Protection Level
VESD
Note 3: Specifications with minimum and maximum limits are 100% production tested at TA = +25°C and are guaranteed over the
operating temperature range by design and characterization. Actual typical values may vary and are not guaranteed.
Note 4: Guaranteed by design and bench characterization; not production tested.
www.analog.com
Analog Devices │ 6
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Timing Diagrams
OVERVOLTAGE
EVENT
OVERVOLTAGE
REMOVED
VOV_SENSN (VOV_D)
SENSN
(HVDQ)
GND
ON
DEVICE
ON/OFF
STATUS
tOV_SENSN
(tFP_D)
OFF
GND
+5V
tB,OV_SENSN
(tB,OV_D)
FAULT
0V
GND
Figure 1. Overvoltage Detection on SENSN, HVD+, HVD- Timing Diagram
USB PERIPHERAL
ATTACH
CD1
FAULT
tSENSP_DIS
HOST CONNECTOR VSENSN 5V
CONNECTED
USB DATA PATH
NOT CONNECTED
PERIPHERAL CHARGING CURRENT
2100mA
500mA
2100mA
500mA
FOR CD0 = 0
Figure 2. Peripheral Reset Timing Diagram
www.analog.com
Analog Devices │ 7
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Timing Diagrams (continued)
+3.3V
IN
+14V
V
ON-LOSS = 20log OUT
VIN
NETWORK ANALYZER
SUP
SUPSW
50Ω
VIN
D+ (D-)
V
CROSSTALK = 20log OUT
VIN
50Ω
MAX16984
+3.3V
VOUT
HVD+ (HVD-)
MEAS
REF
ON-LOSS1 = 20log
HVD+
D+
ON-LOSS2 = 20log
HVDD-
CROSSTALK1 = 20log
HVD+
D-
CROSSTALK2 = 20log
HVDD+
ENBUCK
50Ω
50Ω
GND
ON-LOSS IS MEASURED BETWEEN D+ AND HVD+, OR D- AND HVD-.
CROSSTALK IS MEASURED FROM ONE CHANNEL TO THE OTHER CHANNEL.
SIGNAL DIRECTION THROUGH SWITCH IS REVERSED; WORST VALUES ARE RECORDED.
Figure 3. On-Channel -3dB Bandwidth and Crosstalk
+3.3V
IN
+14V
SUP
SUPSW
MAX16984
D_ OR
HVD_
CAPACITANCE
METER
+3.3V
ENBUCK
GND
Figure 4. On-Capacitance
www.analog.com
Analog Devices │ 8
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Timing Diagrams (continued)
MAX16984
INPUT+
RS
D+
HVD+
OUT+
RISE-TIME PROPAGATION DELAY = tPLHX OR tPLHY
FALL-TIME PROPAGATION DELAY = tPHLX OR tPHLY
tSK(O) = |tPLHX - tPLHY| OR |tPHLX - tPHLY|
tSK(P) = |tPLHX - tPHLX| OR |tPLHY - tPHLY|
RL
INPUT-
RS
D-
HVD-
OUTRL
IN
VIL TO VIH
tINFALL
tINRISE
V+
90%
VINPUT+
90%
50%
50%
10%
0V
10%
V+
VINPUT-
50%
50%
0V
tOUTRISE
tPLHX
tOUTFALL
tPHLX
V+
90%
VOUT+
90%
50%
50%
10%
0V
10%
V+
50%
VOUT-
50%
0V
tPHLY
tPLHY
Figure 5. Propagation Delay and Output Skew
www.analog.com
Analog Devices │ 9
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
STARTUP
VSUP RISING
STARTUP
VIN RISING
MAX16984 toc01
MAX16984 toc02
2V/div
2V/div
VFAULT
10V/div
VSUP
VFAULT
2V/div
2V/div
VIN
VBIAS
2V/div
500mV/div
VBIAS
VIN = 3.3V
VENBUCK = VSUP = 14V
VENBUCK = VSUP = 14V
100µs/div
10µs/div
STARTUP
ENBUCK RISING
SUPPLY CURRENT vs. VOLTAGE
(SKIP MODE, NO LOAD, 2.2MHz)
MAX16984 toc03
8000
2V/div
VFAULT
VIN = VENBUCK = 3.3V
VSYNC = 0V
fSW = 2.2MHz
ILOAD = 0A
7000
2V/div
2V/div
VBIAS
2V/div
ISUP (µA)
6000
VENBUCK
VSENSP
5000
4000
TA = -40°C
3000
TA = +125°C
2000
VIN = 3.3V
VSUP = 14V
ILOAD = 2.1A
MAX16984 toc04
VHVD+
TA = +25°C
1000
0
4.5
2ms/div
9.5
14.5
19.5
24.5
VSUP (V)
SUPPLY CURRENT
vs. VOLTAGE (SHUTDOWN)
12
TA = +125°C
TA = +25°C
8
6
SKIP 400kHz
SKIP 2.2MHz
70
60
PWM 400kHz
50
40
30
4
10
0
4.5
9.5
PWM 2.2MHz
20
TA = -40°C
2
14.5
VSUP (V)
www.analog.com
80
EFFICIENCY (%)
ISUP (µA)
10
90
MAX16984 toc06
MAX16984 toc05
VIN = 0V
VENBUCK = 0V
14
EFFICIENCY vs. LOAD CURRENT
100
19.5
24.5
0
0.003
VSUP = 14V
0.030
0.300
3.000
ILOAD (A)
Analog Devices │ 10
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
fSW vs. RFOSC
fSW vs. RFOSC
5
MEASURED FOSC
2.0
4
1.9
3
THEORETICAL FOSC
1.8
2
-1
0.20
12
13
1
0
55
SENSP LOAD REGULATION
5.06
SKIP RFBMAX = 3.5kI
5.12
5.10
5.08
PWM RFBMAX = 0I
SKIP RFBMAX = 0I
5.06
5.04
5.04
PWM RFBMAX = 0I
5.02
VSUP = 14V
fSW = 400kHz
150
50
100
150
VSENSP, VDUT (V)
5.5
5.0
VDUT (RFBMAX = 0I)
VSUP = 14V
VSYNC = 0V
fSW = 2MHz
VDUT (RFBMAX = 3.5kI)
RCABLE = 330mI
VSENSP (RFBMAX = 0I)
3.5
3.0
0
0.5
1.0
1.5
ILOAD (A)
www.analog.com
VSUP = 14V
VSYNC = 0V
fSW = 400kHz
VDUT (RFBMAX = 3.5kI)
RCABLE = 330mI
200
0.5
0
1.0
2.0
1.5
2.0
2.5
ILOAD (A)
6
OUTPUT-VOLTAGE CHANGE (%)
MAX16984 toc12
VSENSP (RFBMAX = 3.5kI)
4.0
VDUT (RFBMAX = 0I)
4.0
SENSP LINE REGULATION
(ILOAD = 2.1A)
VSENSP, VDUT LOAD REGULATION
4.5
4.5
ILOAD (mA)
ILOAD (mA)
6.0
5.0
3.0
0
200
5.5
MAX16984 toc13
100
VSENSP (RFBMAX = 3.5kI)
3.5
VSUP = 14V
fSW = 2.2MHz
5.00
50
0
-2
80
75
VSENSP (RFBMAX = 0I)
PWM RFBMAX = 3.35kI
5.02
5.00
6.0
VSENSP, VDUT (V)
SKIP RFBMAX = 0I
MAX16984 toc10
MAX16984 toc09
5.14
VSENSP (V)
VSENSP (V)
PWM RFBMAX = 3.5kI
5.08
70
VSENSP, VDUT LOAD REGULATION
5.16
SKIP RFBMAX = 3.5kI
5.10
65
SENSP LOAD REGULATION
5.14
5.12
60
RFOSC (kI)
RFOSC (kI)
5.16
-1
fSW = 29.8MHz·kI/RFOSC
50
15
14
2
0.30
0.25
11
3
0.35
0
fSW = 26.4MHz·kI/RFOSC
MEASURED FOSC
0.40
1.6
1.5
4
0.45
1
6
5
0.50
1.7
7
MAX16984 toc11
2.1
0.55
8
ERROR (%)
6
2.2
THEORETICAL FOSC
0.60
7
MAX16984 toc08
2.3
8
ERROR (%)
SWITCHING FREQUENCY (MHz)
2.4
0.65
9
SWITCHING FREQUENCY (MHz)
MAX16984 toc07
2.5
4
%(RFBMAX = 0I)
2
0
-2
-4
%(RFBMAX = 3.5kI)
-6
2.5
4
6
8 10 12 14 16 18 20 22 24 26 28
INPUT VOLTAGE (V)
Analog Devices │ 11
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
LOAD STEP RESPONSE
(80mA TO 2.1A)
LOAD STEP RESPONSE
(80mA TO 1A)
MAX16984 toc15
MAX16984 toc14
VDUT
100mV/div
+5V OFFSET
VSENSN
200mV/div
+5V OFFSET
100mV/div
+5V OFFSET
VSENSN
500mV/div
+5V OFFSET
IOUT
500mA/div
IDUT
1A/div
100µs/div
100µs/div
LOAD STEP RESPONSE
(END OF CABLE)
SENSN SHORT TO GND
MAX16984 toc16
MAX16984 toc17
5.15
0-0.5A
0.5-1A
1-1.5A
1.5-2.1A
5.10
VDUT (V)
VDUT
VFAULT
2V/div
VSENSN
5.05
2V/div
5.00
RCABLE = 400mI
RFBMAX = 3.75kI
VFBPER = 0V
4.95
2A/div
IL
4.90
-0.2 -0.1
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7
1µs/div
TIME (ms)
SENSN
SHORT TO BATTERY (14V)
80
VFAULT
70
60
5V/div
VSENSN
IL
2A/div
FREQUENCY
2V/div
MAX16984 toc19
SENSO THRESHOLD RISING
MAX16984 toc18
-40°C
+25°C
+105°C
50
40
30
20
10
0
1.160
1.165
1.170
1.175
1.180
1.185
1.190
1.195
1.200
1.205
1.210
1.215
1.220
1.225
1.230
1.235
1.240
1.245
1.250
1.255
1.260
4µs/div
VSENSO (V)
www.analog.com
Analog Devices │ 12
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MEASURED
CURRENT LIMIT
8
80
7
70
6
5
1.5
1.0
90
4
% ERROR
CALCULATED
CURRENT LIMIT
0.5
0
4000
9000
14,000
60
50
40
3
30
2
20
1
10
0
0
19,000
1.035 1.045 1.055 1.065 1.075 1.085 1.095
1.040 1.050 1.060 1.070 1.080 1.090 1.100
SENSP ANALOG GAIN (V/V)
R_SENSO (I)
25
MAX16984 toc22
-40°C
+25°C
+105°C
20
35
30
40
30
FREQUENCY
25
FREQUENCY
FREQUENCY
50
-40°C
+25°C
+105°C
15
10
20
20
15
10
5
10
0
5
0
4.96
4.98
4.99
5.01
5.02
5.04
5.05
5.07
5.08
5.10
5.11
5.13
5.14
5.16
0
0.70
0.76
0.82
0.88
0.94
1.00
1.06
1.12
1.18
1.24
1.30
1.36
1.42
1.48
1.54
1.60
0.519 0.525 0.531 0.537 0.543 0.549
0.522 0.528 0.534 0.540 0.546 0.552
SENSP ANALOG GAIN (V/V)
LOAD REGULATION (%/A)
VSENSP (V)
HVD+/HVD- LEAKAGE CURRENT
vs. TEMPERATURE
MAXIMUM CURRENT (A)
2.8
2.6
2.4
2.2
TA = +85°C
2.0
1.8
TA = +125°C
1.6
VSUP = 14V
RSENSO = 0I
RFBMAX = 9.53kI
L = 15µH
TA = +105°C
1.4
1.2
400
760
1120
1480
fSW (kHz)
www.analog.com
1840
2200
11.9
11.6
11.3
11.0
10.7
10.4
10.1
9.8
9.5
9.2
8.9
8.6
8.3
8.0
MAX16984 toc26
MAX16984 toc25
3.0
HVD+/HVD- CURRENT +18V (µA)
MAXIMUM USB LOAD CURRENT vs. fSW
3.2
HVD+/HVDSHORTED TO +5V
-15
10
4.5
4.0
HVD+/HVDSHORTED TO +5V
3.5
3.0
VSUP = 14.0V
VIN = 3.3V
VENBUCK = 3.3V
-40
5.0
35
60
85
HVD+/HVD- CURRENT +5V (µA)
60
-40°C
+25°C
+105°C
NO-LOAD OUTPUT VOLTAGE (VSENSP)
VSUP = 14V
LOAD REGULATION
VSUP = 14V
MAX16984 toc23
SENSP ANALOG ADJUST GAIN (ASENSP)
VFBPER = 3.3V
70
-40°C
+25°C
+105°C
MAX16984 toc24
2.0
100
9
FREQUENCY
CURRENT (A)
2.5
10
ERROR (%)
MAX16984 toc20
3.0
MAX16984 toc21
SENSP ANALOG ADJUST GAIN (ASENSP)
VFBPER = 0V
R_SENSO vs. USB CURRENT LIMIT
2.5
105
TEMPERATURE (°C)
Analog Devices │ 13
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
DATA SWITCH RON
vs. APPLIED DATA VOLTAGE
11.0
HVD+/HVDSHORTED TO +18V
10.6
10.2
4.1
HVD+/HVDSHORTED TO +5V
3.7
3.3
9.8
9.4
2.9
VSUP = 0V
VIN = 0V
9.0
-40
-15
10
35
60
85
4.6
4.4
4.2
4.0
3.8
3.6
VIN = 3.3V
IL = 40mA
3.4
3.2
2.5
0
105
0.6
1.2
1.8
2.4
3.0
3.6
TEMPERATURE (°C)
APPLIED DATA VOLTAGE (V)
DATA SWITCH RON
vs. APPLIED DATA VOLTAGE
HVD+/HVD- SHORT TO BATTERY (14V)
POWERED AND ENABLED
MAX16984 toc30
MAX16984 toc29
8
TA = +105°C
6
VFAULT
TA = +25°C
RON (I)
MAX16984 toc28
4.5
RON (I)
HVD+/HVD- CURRENT +18V (µA)
11.4
4.8
4.9
HVD+/HVD- CURRENT +5V (µA)
MAX16984 toc27
HVD+/HVD- LEAKAGE CURRENT
vs. TEMPERATURE
2V/div
VSENSN
4
2V/div
VD+
2
TA = -40°C
VIN = 3.3V
IL = 40mA
0
0
0.6
1.2
1.8
2.4
3.0
5V/div
10V/div
VHVD+
4ms/div
3.6
APPLIED DATA VOLTAGE (V)
HVD+ /HVD- SHORT TO
BATTERY (14V) UNPOWERED
CROSSTALK vs. FREQUENCY
MAX16984 toc31
MAX16984 toc32
0
VD+
500mV/div
5V/div
CROSSTALK (dB)
-10
-20
-30
-40
-50
VHVD+
-60
2µs/div
10
100
1000
FREQUENCY (MHz)
www.analog.com
Analog Devices │ 14
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
14
BST 22
LX 23
LX 24
MAX16984
SUPSW 25
SUPSW 26
PGND 27
EP
+
23
LX
24
LX
25
9
D+
SUPSW
27
8
IN
PGND
28
+
1
2
3
4
5
6
7
1
2
3
SYNC
26
MAX16984RACIL
MAX16984SACIL
FAULT
SUPSW
15
ENBUCK
D-
16
FBPER
10
17
I.C.
11
N.C.
18
CD1
HVD-
19
CD0
12
20
FOSC
HVD+
21
SYNC
13
FBMAX
BST
FBCAP
22
FAULT
ENBUCK 28
GND
NC
TQFN/QFND
4
5
6
7
14
GND
13
HVD+
12
HVD-
11
D-
10
D+
9
IN
8
FBPER
I.C.
15
SENSO
FBMAX
16
CD1
FBCAP
17
SENSN
SENSO
18
CD0
SENSN
19
SENSP
SENSP
20
FOSC
BIAS
21
TOP VIEW
BIAS
SUP
TOP VIEW
SUP
Pin Configuration
CPQFN
Pin Description
PIN
NAME
FUNCTION
TQFN/
QFND
CPQFN
1
2
FAULT
Active-Low Open-Drain Fault Indicator Output. Connect a 100kΩ pullup resistor to IN.
2
3
SYNC
Synchronization Input. The device synchronizes to an external signal applied to SYNC. When
connected to GND or unconnected, skip mode is allowed under light loads. See Table 1. When
connected to a clock source or IN, forced-PWM (FPWM) mode is enabled.
3
4
FOSC
Resistor-Programmable Switching-Frequency Setting Control Input. Connect a resistor from
FOSC to GND to set the switching frequency.
4
5
CD0
5
6
CD1
Charger Detection Configuration Bit 1
6
7
I.C.
Internal Connection. Must be connected to external GND.
7
8
FBPER
8
9
IN
Logic Enable Input. Connect to I/O voltage of USB transceiver. IN is also used for clamping
during overvoltage events on HVD+ or HVD-. Connect a 1µF ceramic capacitor from IN to
GND.
9
10
D+
USB Differential Data D+ Input. Connect D+ to low-voltage USB transceiver D+ pin.
10
11
D-
USB Differential Data D- Input. Connect D- to low-voltage USB transceiver D- pin.
11
22
N.C.
www.analog.com
Charger Detection Configuration Bit 0
Digital Input. Used to select voltage feedback adjustment percentage.
No Connection
Analog Devices │ 15
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Pin Description (continued)
PIN
NAME
FUNCTION
TQFN/
QFND
CPQFN
12
12
HVD-
High-Voltage-Protected USB Differential Data D- Output. Connect HVD- directly to the USB
connector D- pin.
13
13
HVD+
High-Voltage-Protected USB Differential Data D+ Output. Connect HVD+ directly to the USB
connector D+ pin.
14
14
GND
Analog Ground
15
15
FBMAX
Current-Sense Amp Output. Connect a resistor and capacitor to GND to set the voltageadjustment bandwidth and the USB DC current level at which maximum voltage-feedback
adjustment is reached.
16
16
FBCAP
External Capacitor Connection. Connect a 10pF capacitor to GND.
17
17
SENSO
Current-Sense Amp Output. Connect a resistor and capacitor to GND to set the maximum USB
DC current limit.
18
18
SENSN
Current-Sense Amp Negative Input. Connect to negative terminal of current-sense resistor.
19
19
SENSP
DC-DC Converter Feedback Input and Current-Sense Amp Positive Input. Connect to positive
terminal of current-sense resistor and the main output of the converter. Used for internal
voltage regulation loop.
20
20
BIAS
5V Linear Regulator Output. Connect a 1µF ceramic capacitor from BIAS to GND. BIAS powers
up the internal circuitry.
21
21
SUP
Voltage Supply Input. SUP is the supply pin for the internal linear regulator. Connect a minimum
of 4.7µF capacitor from SUP to GND close to the IC.
22
23
BST
23, 24
24, 25
LX
25, 26
26, 27
SUPSW
27
28
PGND
28
1
ENBUCK
—
—
EP
www.analog.com
High-Side Driver Supply. Connect a 0.1µF capacitor from BST to LX.
Inductor Connection. Connect a rectifying Schottky diode between LX and GND. Connect an
inductor from LX to the DC-DC converter output (SENSP).
Internal High-Side Switch-Supply Input. SUPSW provides power to the internal switch. Connect
a 4.7µF ceramic capacitor in parallel with a 47µF capacitor from SUPSW to PGND. See the
DC-DC Input Capacitor Selection section.
Power Ground
Battery-Compatible Enable Input. Drive ENBUCK low/high to disable/enable the switching
regulator.
Exposed Pad. Connect EP to a large-area contiguous copper ground plane for effective power
dissipation. Do not use as the only IC ground connection. EP must be connected to GND.
Analog Devices │ 16
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Functional Diagram
Detailed Description
IN
MAX16984
FAULT
I/O
CONTROL AND
DIAGNOSTICS
CD1
CD0
HVD-
D-
HVD+
D+
GND
USB AUTO DCP, CDP,
iPhone, iPad
CHARGER DETECTION
SUPSW
BST
SUP
LX
2.1A
FPWM
DC-DC
PGND
ENBUCK
ENBUCK
SYNC
FOSC
BIAS
BIAS
REF
The high-efficiency step-down DC-DC converter
operates from a voltage up to 28V and is protected from
load-dump transients up to 42V. The device includes
resistor-programmable frequency selection from 220kHz
to 2.2MHz to allow optimization of efficiency, noise, and
board space based on the application requirements. The
converter can deliver up to 2.1A of continuous current at
105°C.
The MAX16984 also includes a high-side current-sense
amplifier and configurable feedback-adjustment circuit
designed to provide automatic USB voltage adjustment to
compensate for voltage drops in captive cables associated
with automotive applications.
System Enable (IN)
SENSP
SENSO
SENSN
FBMAX
CURRENTSENSE AMP
FEEDBACK
ADJUSTMENT
www.analog.com
The USB protection switches provide high-ESD and
short-circuit protection for the low-voltage internal data
lines of the multimedia processor’s USB transceiver
and support USB Hi-Speed (480Mbps) and USB FullSpeed (12Mbps) pass-through operation. The MAX16984
features integrated host-charger port-detection circuitry
adhering to the USB 2.0 Battery Charging Specification
BC1.2 and also includes dedicated bias resistors for iPod/
iPhone 1.0A and iPad 2.1A dedicated charging modes.
Power-Up and Enabling
I LIMIT
FEEDBACK
FBCAP
The MAX16984 combines a 5V/2.1A automotive grade
step-down converter, a USB host charger adapter
emulator, and USB protection switches. It is designed for
high-power USB ports in automotive radio, navigation,
connectivity, and USB hub applications.
FBPER
IN is used as the main enable to the MAX16984 and is
also used to clamp the D+ and D- pins during an ESD
and short-to-battery on the HVD+ and HVD- pins. This
clamping protects the downstream USB transceiver. The
IN pin contains an overvoltage lockout that disables the
data switches if IN is above VIN_OVLO. Bypass IN with a
1FF capacitor and connect it to the same 3.3V supply as
shared with the multimedia processor’s USB transceiver.
If IN is logic-high, the protection switches are enabled
and the USB switches operate in one of four modes per
the CD0 and CD1 inputs. If IN is at a logic-low level, SUP
power consumption is reduced and the device enters a
standby low-quiescent level.
Analog Devices │ 17
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Linear Regulator Output (BIAS)
BIAS is the output of a 5V linear regulator that powers
the internal circuitry for the MAX16984. BIAS is internally
powered from SUP and automatically powers up when IN
is high and VSUP exceeds approximately 2.7V. The BIAS
output contains an under voltage lockout that keeps the
internal circuitry disabled when BIAS is below VUV_BIAS.
The linear regulator automatically powers down when IN is
low and a low 6µA (typ) shutdown current mode is entered.
Bypass BIAS to GND with a 1µF ceramic capacitor.
DC-DC Enable (ENBUCK)
The buck regulator on MAX16984 is activated by
driving ENBUCK high and disabled by driving ENBUCK
low. ENBUCK is compatible with inputs from automotive battery level down to 3.3V. Connect ENBUCK to the
enable output of the USB transceiver controller in a typical
application. This allows the USB controller to enable and
disable the USB power port via software commands (see the
Functional Diagram). ENBUCK can be directly connected
to SUP for dedicated USB power port applications that do
not have the USB transceiver controlling ENBUCK.
Power-On Sequence
For typical radio and navigation applications, the SUP and
SUPSW are connected together and connected to the
vehicle battery. SUP and IN have no power-up sequence
requirements, however, IN is typically enabled after SUP.
Step-Down DC-DC Regulator
Step-Down Regulator
The switching regulator is a high input voltage, constantfrequency, current-mode step-down DC-DC converter
delivering output current up to 2.1A. The converter has
an internal high-side n-channel switch and uses a low
forward-drop freewheeling Schottky diode for rectification.
There is a small low-side n-channel switch to maintain
fixed frequency under light loads. For lower quiescent
current operation requirements, the low-side n-channel
switch can be disabled to allow skip mode operation
under light loads.
Wide Input Voltage Range
The device includes two separate supply inputs, SUP
and SUPSW, specified for a wide 4.5V to 28V input voltage range. SUP provides power to the internal BIAS
linear regulator, and SUPSW provides power to the
internal power switch. Certain conditions such as cold
crank can cause the voltage at output to drop below the
www.analog.com
programmed output voltage of 5.05V. As the input voltage approaches the output voltage, the device enters
dropout and the effective duty cycle of the high-side FET
approaches 97%. When the switching regulator is in dropout, the switching frequency is reduced.
Output Voltage (SENSP)
The MAX16984 has a precision internal feedback network
connected to SENSP that is used to set the output voltage
of the DC-DC converter. The network nominally sets the
average DC-DC converter output voltage to 5.05V when
in forced-PWM (FPWM) operation and to 5.09V when
operating in skip mode.
Soft-Start
When the DC-DC converter is enabled, the regulator
soft-starts by gradually ramping up the output voltage
from 0 to 5.05V in approximately 9ms. This soft-start
feature reduces inrush current during startup. Soft-start
is guaranteed into compliant USB loads (see the USB
Loads section).
Switching Frequency (FOSC, SYNC)
The MAX16984 DC-DC switching frequency can be set
by either its internal oscillator or by synchronization
to an external clock on the SYNC pin. The internal
oscillator frequency (fSW) is set by a resistor connected
from FOSC to GND (see the Applications Information
section). When operating from its internal oscillator and at
no load, the MAX16984 can be operated in FPWM mode or
is allowed to enter skip mode operation. See Table 1. When
syncing to an external clock, duty cycle must be between
40% and 60%, clock input frequency must be within ±20%
of the resistor-set frequency, and frequency cannot exceed
2.3MHz.
Forced-PWM Operation
While operating from a clocked signal on the SYNC
pin, the MAX16984 is in FPWM mode operation at all
times. While operating from its internal oscillator, FPWM
operation can be entered by connecting the SYNC logichigh. The MAX16984 maintains fixed-frequency PWM
operation over all load conditions with the SYNC pin
logic-high or being clocked by an external clock source.
Additionally, the MAX16984 can intelligently enter FPWM
mode and exit skip mode (Table 1) if a portable device
is plugged in by determining if the portable device is
actively consuming more than 4% of the programmed
current limit on SENSO (see the Current Limit section).
Analog Devices │ 18
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Table 1. DC-DC Converter Forced-PWM Mode and Skip Mode Operation Truth Table
SYNC
1
CD1 CD0
X
CDP
DETECTION
X
USB LOAD
CURRENT
DCP
DETECTION
DC-DC CONVERTER
OPERATION
X
X
X
FPWM Mode: Continuous
X
Allow Skip Mode: No USB load
detected
0
X
X
X
VSENSO <
48mV
0
X
X
X
VSENSO >
48mV
X
FPWM Mode: USB load detected
0
0
1
(HVD+ or HVD-)
> VIH
X
X
FPWM Mode: USB device
connected to port
0
0
1
(HVD+ and HVD-)
< VIL
VSENSO <
48mV
X
Allow Skip Mode: USB device not
connected to port
0
1
X
X
VSENSO <
48mV
(HVD- > VDM1F) & (HVD+ < VDPR)
Allow Skip Mode: No USB load
detected
0
1
X
X
VSENSO >
48mV
(HVD- > VDM1F) & (HVD+ < VDPR)
FPWM Mode: USB load detected
0
1
X
X
X
(HVD- > VDM1F) & (HVD+ > VDPR)
FPWM Mode: USB device
detected
0
1
X
X
X
(HVD- < VDM1F)
FPWM Mode: USB device
detected
Intelligent Skip Mode Operation
Current Limit
If the SYNC pin is logic-low, the MAX16984 is allowed
to leave FPWM mode and enter skip mode operation
(Table 1). While in skip mode, the high-side FET is turned
on until the current in the inductor is ramped up to 300mA
(typ) peak value and the internal feedback voltage is above
the regulation voltage (1.2V typ). At this point, both the
high-side and low-side FETs are turned off. Depending on
the choice of the output capacitor and the load current, the
high-side FET turns on again when SENSP drops below
5.05V (typ).
The MAX16984 limits the USB load current using both
a fixed internal peak current threshold of the DC-DC
converter and a user-configurable external USB load
current-sense amplifier threshold (see the Current-Sense
Output (SENSO) section). This allows the current limit to
be adjusted between 500mA and 2.1A, depending on the
application requirements, and protects the DC-DC
converter in the event of a fault. Upon exceeding
either the internal or user-programmable current-limit
thresholds, the high-side FET is immediately turned off and
current-limit algorithms are initiated. When the external
current limit lasts for longer than 16.5ms, FAULT asserts.
If both the USB current limit is detected and the output
voltage exceeds 4.75V for longer than 16.5ms, the DC-DC
converter resets. If the internal peak current threshold
is exceeded for four consecutive cycles and the output
voltage is less than 2.0V, the high-side FET is turned off
for 16ms to allow the inductor current to discharge and a
soft-start sequence is then initiated.
Spread-Spectrum Option
Spread spectrum is offered to improve EMI performance
of the MAX16984. The MAX16984S has an integrated
spread-spectrum oscillator, and the internal operating
frequency modulates up to ±3.25% relative to the internally
generated operating frequency, resulting in a total spreadspectrum range of 6.5%. The internal spread spectrum
does not interfere with the external clock applied on the
SYNC pin. It is active only when the MAX16984 is running
with internally generated switching frequency.
www.analog.com
Analog Devices │ 19
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Output Short-Circuit Protection
The output of the DC-DC converter (SENSP, SENSN)
is protected against both short-to-ground and short-tobattery conditions. If a short-to-ground or undervoltage is
encountered on SENSP, the device is disabled for 16ms
(typ) and then reattempts soft-start. This pattern repeats
until the short circuit has been removed.
If a short-to-battery is encountered (VSENSN > VOVSENSN), the device stops switching and the FAULT pin is
asserted after 8µs. The host system should monitor the
FAULT output and disable the ENBUCK if multiple FAULT
events occur to minimize operating current.
Thermal-Overload Protection
Thermal-overload protection limits the total power
dissipation in the MAX16984. A thermal-protection
circuit monitors the die temperature. If the die temperature
exceeds +174°C, the device shuts down, allowing it to
cool. Once the device has cooled by 30°C, the device is
enabled again. This results in a pulsed output during continuous thermal-overload conditions. The thermal-overload
protection protects the device in the event of fault
conditions. For continuous operation, do not exceed the
absolute maximum junction temperature of +150°C.
USB Current Limit and Captive Cable-Voltage
Adjustment
Current-Sense Amplifier (SENSP, SENSN)
The MAX16984 features an internal USB load currentsense amplifier to monitor the load current being pulled by
the USB port. The (VSENSP - VSENSN) voltage sets an output current at both SENSO and FBMAX equal to 2.5mA/V.
Choose a sense resistor from SENSP to SENSN to limit
the differential voltage across SENSP-SENSN to 120mV.
Current-Sense Output (SENSO)
A resistor to ground on the SENSO pin results in a voltage representing the USB load current. Upon crossing
the fixed internal threshold of 1.2V, the high-side FET is
immediately turned off, the low-side FET is turned on,
and the USB load current is reduced until the voltage at
SENSO falls below the 1.2V threshold. If the load current
exceeds the USB current limit for longer than 16.5ms, a
FAULT is asserted. For proper functionality, limit the voltage at SENSO to 2.0V.
Current Feedback Adjustment
cables in automotive applications. The feature set allows
for the user to set the maximum amount the voltage can
be raised and set the desired operating bandwidth of the
adjustment.
Feedback Percentage (FBPER)
The FBPER pin allows the user to set the maximum
allowable percentage to either +25% (VFBPER = 0V)
or +12.5% (VFBPER = 3.3V). Set the FBPER pin such
that the percentage of voltage adjustment needed is
minimized for the application in the event of a fault.
Maximum Feedback Adjustment (FBMAX)
A resistor to ground on the FBMAX pin results in a voltage
representing the USB load current. The output voltage of
the DC-DC converter increases linearly as the voltage at
FBMAX increases up to 1.2V to maintain voltage at the
portable device (VDUT) that meets USB specification. Upon
crossing the fixed internal threshold of 1.2V, the DC-DC
output voltage remains unchanged. For proper functionality, limit the voltage at FBMAX to 2.0V. A capacitor to
GND is also needed on the FBMAX pin to limit the bandwidth of the feedback adjustment. See Figure 6.
USB Protection Switches
HVD+ and HVD- Protection
The MAX16984 provides automotive grade ESD and shortcircuit protection for the low-voltage internal USB data
lines of high-integration multimedia processors. HVD+/
HVD- protection consists of ESD and OVP (overvoltage
protection) for both 12Mbps and 480Mbps USB transceiver
applications. This is accomplished with an extremely lowcapacitance, high-voltage FET in series with the D+ and
D- data paths.
No external ESD protection diodes are required when
using the MAX16984. The HVD+ and HVD- ESD protection
features include protection to ±15kV Air/±8kV Contact on
the HVD+ and HVD- outputs to the IEC 61000-4-2 model
and 330Ω, 330pF ESD model.
The HVD+ and HVD- short-circuit protection features
include short to +18V battery as well as short to +5V on
the protected HVD+ and HVD- outputs. This is provided to
protect against shorted conditions in the vehicle harness
and prevent damage to the low-voltage USB transceiver.
Short-to-GND protection is provided by the upstream USB
transceiver.
The MAX16984 has multiple user-configurable features
to adjust the DC-DC converter output voltage higher to
help overcome voltage drops associated with captive
www.analog.com
Analog Devices │ 20
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
USB LOAD
RS
50mΩ
SENSP
SENSN
±5V
CLAMP
MAX16984
DUAL CURRENT SENSE
FBPER = 0: 1.069 V/V
FBPER = 1: 0.535 V/V
FBMAX
TO FEEDBACK
ERROR AMP
0.6V
0 TO 1.2V
IOUT
RFBMAX
USB CURRENT LIMIT
IOUT
1.2V
FBCAP
SENSO
CFBCAP
0 TO 1.2V
RSENSO
CFBMAX
EXTERNAL
RESISTOR
FILTER
CAP
CSENSO
EXTERNAL
RESISTOR
FILTER
CAP
Figure 6. USB Current-Sense Amplifier, USB Current Limit, and USB Voltage Feedback Adjustment
USB Host Adapter Emulator
The Hi-Speed USB protection switches integrate the
latest USB-IF Battery Charging Specification Revision 1.2
CDP and DCP circuitry, both the 1.0A and 2.1A resistor
bias options for Apple-compliant devices, and the industry
legacy USB D+ short to D- charge detection using data
line pullup.
HVD+ and HVD- Operation (CD1, CD0)
The MAX16984 features dual digital inputs, CD1 and CD0,
for mode selection of the HVD+ and HVD- pins (Table 2).
Connect CD1/CD0 to a logic-level low for normal USB
Hi-Speed (HS) pass-through mode. Connect CD1/CD0 to
www.analog.com
a logic-level low/high for USB low-speed (LS) and USB
full-speed (FS) data transmission and charging downstream port (CDP) mode. See Table 1 for CDP mode and
Figure 7 for a detailed description of all modes.
Hi-Speed Pass-Through Mode (CD1/CD0 = low/low)
HS pass-through mode provides true pass-through operation for USB HS (480Mbps) data signals and disables the
CDP circuitry. Place the device into this mode when the
USB transceiver requests to enter HS mode. See Table 2.
Analog Devices │ 21
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Table 2. Data Switch Mode Truth Table
DEVICE INPUTS
INTERNAL LOGIC
IN
CD1
CD0
SA
SB
ENAUTO
ENHOST
DATA SWITCH MODE
0
X
X
X
X
X
X
Off
1
0
0
1
0
0
0
HS Pass-Through
1
0
1
1
0
0
1
FS/LS with CDP
1
1
0
0
1
1
0
DCP/Apple 2.1A with Auto Detection
1
1
1
0
1
1
0
DCP/Apple 1.0A with Auto Detection
IN
SA
USB 2.0 CDP
D+
HVD+
CLAMP
SA
HVD-
DBIAS
S1
SB
iPhone
S1
RP1
75kΩ
S3
RM1
43.25kΩ
iPad
SB
S2
LOGIC LOW < 0.8V
LOGIC HIGH > 2.0V
S1
iPhone/iPad
AND USB 2.0
AUTO DCP
CHARGER
DETECTION
S4
100µA
325mV
S2
iPhone
600mV
iPad
S2
500kΩ
RP2
49.9kΩ
RM2
49.9kΩ
DM1
BIAS
7.8ms DELAY
RISING EDGE
iPad
R
Q
S
Q
MAX16984
DP
977µs DELAY
RISING EDGE
0.572 x VBUS
iPhone
0.46 x VBUS
iPad
DM2
0.30 x VBUS
2.0s DELAY
RISING EDGE
IN
0.07 x VBUS
ENAUTO
CD0
CD1
ENHOST
CONTROL
LOGIC
ONE SHOT
iPhone
iPad
ONE SHOT
INTERNAL
ENBUCK
SA
SB
ENBUCK
Figure 7. Data Switches and Host Adapter Emulator
www.analog.com
Analog Devices │ 22
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Low-Speed/Full-Speed
Mode
with
Downstream Port (CD1/CD0 = low/high)
Charging
After a USB-compliant portable device detects VBUS, it is
allowed to check if the host device is a CDP by applying
a voltage to HVD+ and checking the voltage on HVD-. At
this time, it is assumed that HVD+ and HVD- are logiclow, which means that the voltage is less than 0.8V. Then
the port-detection circuit is enabled and switch 3 is on
(Figure 7). The portable device then drives HVD+ to 0.6V
(typ). The comparator closes switch 4 and the HVD- line
is then driven to 0.6V (typ). The portable device can now
detect that it is connected to a charging port.
provide the proper Apple-compliant iPad bias voltage.
Data switches SA are opened and switches SB are closed
(Figure 7). Initially, the iPad termination resistors are
presented on the HVD+/- pins, the MAX16984 then
monitors the voltages at HVD+ and HVD- to determine the
type of device attached.
If the voltage at HVD- is +1.5V (typ) (VBUS x 0.3) or
higher, and the voltage at HVD+ is +2.86V (typ) (VBUS
x 0.572) or lower, the state remains unchanged and the
iPad termination resistors remain present.
When an FS device connects, it pulls the HVD+ line logichigh to a voltage greater than 2V. Then switch 3 opens,
the positive input of the comparator is forced to zero,
and switch 4 is also opened. Because HVD- is low, the
portable device detects that it is connected to a CDP.
If the voltage at HVD- is forced below the +1.5V (typ)
(VBIAS x 0.3) threshold or if the voltage at HVD+ is forced
higher than the +2.86V (typ) (VBIAS x 0.572) threshold,
the internal switch disconnects HVD- and HVD+ from
the resistor-divider (iPad switch open) and HVD+ and
HVD- are shorted together for dedicated charging mode
(S2 closed).
When a LS device connects, it pulls the HVD- line logichigh (after it has stopped driving HVD+ to 0.6V). Because
HVD+ stays low, the portable device detects that it is
connected to a CDP.
Once the charging voltage is removed, the short between
HVD+ and HVD- is disconnected and the operation is
restarted with the internal resistor-divider bias voltages
appearing on HVD+ and HVD-.
When the portable device has connected in LS or FS
mode, either D+ or D- is logic-high upon enumeration,
which disables the charger-detect circuit. A delay is
implemented that closes switch 3 after HVD+ and HVDare logic-low longer than 100µs. This ensures that switch
3 stays off when the logic-high states of D+ and D- do not
overlap.
USB-IF Dedicated Charging Port and Apple 1A with
Auto Detection (CD1/CD0 = high/high)
If a Hi-Speed-capable device connects to the port and
CD1/CD0 = low/high, it can detect that it is connected
to a CDP. Upon enumeration, and before entering HS
mode, the host system microprocessor must query the
USB transceiver to determine if HS mode is needed. If
so, it must drive the CD0 input low to disable the portdetection circuit and enter USB HS mode. The host system
microprocessor must also query the USB transceiver to
detect when the HS portable device is disconnected or no
longer in HS mode. Once detected, it must drive the CD0
input high to re-enable the port-detection circuit for the next
connection sequence. This is needed as the HS differential
logic levels on HVD+ and HVD- are below 500mV.
USB-IF Dedicated Charging Port and Apple 2.1A with
Auto Detection (CD1/CD0 = high/low)
The MAX16984 features an iPad/DCP auto-detection
mode for emulating dedicated iPad 2.1A charging
and USB-IF DCPs. CD1/CD0 must be set high/low to
activate iPad/DCP auto-detection mode. In this mode,
the high-voltage-protected HVD+ and HVD- pins are
disconnected from the low-voltage D+ and D- pins and
are initially connected to internal resistor-dividers to
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The MAX16984 features an iPhone/DCP auto-detection
mode for emulating dedicated iPhone 1.0A charging and
USB-IF DCPs. CD1/CD0 must be set high/high to activate
iPhone/DCP auto-detection mode. In this mode, the highvoltage-protected HVD+ and HVD- pins are disconnected
from the low-voltage D+ and D- pins and are initially
connected to internal resistor-dividers to provide the
proper Apple-compliant iPhone bias voltage. Data switches SA are opened and switches SB are closed (Figure 7).
Initially, the iPhone termination resistors are presented
on the HVD+/- pins. The MAX16984 then monitors the
voltages at HVD+ and HVD- to determine the type of the
device attached.
If the voltage at HVD- is +2.3V (typ) (VBIAS x 0.46) or
higher, and the voltage at HVD+ is +2.3V (typ) or lower,
the state remains unchanged and the iPhone termination
resistors remain present. If the voltage at HVD- is forced
below the +2.3V (typ) threshold, or if the voltage at HVD+
is forced higher than the +2.3V (typ) threshold, the internal
switch disconnects HVD- and HVD+ from the resistordivider (iPhone switch open) and HVD+ and HVD- are
shorted together for dedicated charging mode (S2 closed).
Once the charging voltage is removed, the short between
HVD+ and HVD- is disconnected and the operation is
restarted with the internal resistor-divider bias voltages
appearing on HVD+ and HVD-.
Analog Devices │ 23
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Fault Output (FAULT)
The MAX16984 features an open-drain, active low FAULT
output. Table 3 summarizes the conditions that generate
a fault and actions taken by the MAX16984. The output
remains asserted until the fault condition is removed. The
MAX16984 is designed to eliminate false FAULT reporting
by using an internal deglitch, fault blanking, timer. This
ensures FAULT is not accidentally asserted during normal
operation such as starting into heavy capacitive loads.
Applications Information
DC-DC Switching-Frequency Selection
The switching frequency (fSW) for the MAX16984 is
resistor programmable by connecting resistor (RFOSC)
from FOSC to GND. Select the correct RFOSC value for
the desired switching frequency. For operation between
1.8MHz and 2.2MHz: fSW [MHz] = 26.4/RFOSC, and
for operation between 220kHz and 500kHz: fSW [MHz]
= 29.8/RFOSC, where RFOSC is in kΩ. For example,
a 2.2MHz switching frequency is set with RFOSC =
12kΩ. Higher switching frequencies allow for smaller PCB
area designs with lower inductor values and less output
capacitance. Consequently, peak currents and I2R losses
are lower at higher switching frequencies, but core losses,
gate charge currents, and switching losses increase.
Operation between 500kHz and 1.8MHz is not
recommended to avoid AM band interference.
DC-DC Input Capacitor Selection
The MAX16984 has two main power supply pins to
support multiple power architectures. Bypass SUP with
a 4.7FF ceramic capacitor to GND for proper operation
of the internal BIAS linear regulator. The selection of the
input filter capacitor from SUPSW to PGND reduces the
peak currents drawn from the upstream power source
and reduces noise and voltage ripple on the input caused
by the circuits switching. The input capacitor RMS
current rating requirement (IRMS) is defined by the
following equation:
IRMS = ILOAD(MAX)
VSENSP (VSUPSW − VSENSP )
VSUPSW
IRMS has a maximum value when the input voltage
equals twice the output voltage (VSUPSW = 2VSENSP),
so IRMS(MAX) = ILOAD(MAX)/2.
Table 3. Fault Conditions
EVENT
ACTION TAKEN
Thermal Fault
• If the device is over the thermal limit, the step-down DC-DC regulator is disabled immediately and
FAULT goes low.
• When the thermal fault is removed, the fault is cleared immediately and FAULT goes high.
• After the fault is removed, the soft starts begins
Overvoltage on Pins
(HVD+, HVD-, IN)
• An overvoltage at one of these pins immediately switches off all power and data switches. The
step-down DC-DC regulator turns off and the blanking timer turns on.
• If overvoltage persists for 18ms or longer, FAULT goes low.
• When the overvoltage is removed, the fault is cleared immediately and FAULT goes high.
• After the fault is removed, the soft starts begins.
Undervoltage on BIAS
• A BIAS UVLO immediately switches off all power and data switches and resets the digital logic.
• During BIAS UVLO, FAULT is high impedance.
Undervoltage on SENSP
or Overcurrent
• If SENSP is less than 4.75V for more than 10ms, FAULT goes low.
• If USB current limit is high for more than 16.5ms, FAULT goes low.
• If USB current limit is high and SENSP is less than 4.75V for more than 16.5ms, the step-down
DC-DC regulator will reset for 16ms then try to start up again.
• If the USB current limit is high and if SENSP is less than 2V, FAULT goes low and the part resets.
• If the step-down DC-DC regulator high-side current limit is high for 4 clock cycles, and if SENSP is
less than 2V, FAULT goes low and the part resets.
Overvoltage on SENSN
• If overvoltage persists for 8μs, FAULT goes low and the step-down DC-DC regulator is disabled.
• After the fault is removed, the soft starts begins.
www.analog.com
Analog Devices │ 24
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Choose an input capacitor that exhibits less than +10°C
self-heating temperature rise at the RMS input current for
optimal long-term reliability.
The input voltage ripple is composed of VQ (caused
by the capacitor discharge) and VESR (caused by the
ESR of the capacitor). Use low-ESR ceramic capacitors
with high ripple current capability at the input. Assume
the contribution from the ESR and capacitor discharge
equal to 50%. Calculate the input capacitance and ESR
required for a specified input voltage ripple using the
following equations:
∆VESR
ESRIN =
∆I
I OUT + L
2
where:
(V
− VSENSP ) × VSENSP
∆IL = SUPSW
VSUPSW × fSW × L
and:
I
× D(1 − D)
V
CIN = OUT
and D = SENSP
∆VQ × fSW
VSUPSW
where IOUT is the maximum output current and D is the
duty cycle.
Bypass SUPSW with a 4.7µF ceramic and 47µF
electrolytic capacitor close to the SUPSW and PGND
pins. Minimize PCB loop area for minimal EMI. Use small
footprint components, such as an 0805 or smaller, to
reduce total parasitic inductance.
DC-DC Output Capacitor Selection
The minimum capacitor required depends on output
voltage, maximum device current capability, and the
error-amplifier voltage gain. Use the following formula to
determine the required output capacitor value:
V
× G CS × GEAMP
C OUT(MIN) = REF
2π × fCO × VOUT
where VREF = 1.2V, GCS = 2.5, fCO = 0.125 x fSW, and
GEAMP = 37.5V/V.
Table 4 lists the recommended inductor and capacitor
values for several different switching frequencies. For
proper functionality, a minimum amount of ceramic
capacitance must be used regardless of fSW. Additional
capacitance for lower switching frequencies can be of the
low-ESR electrolytic type (< 0.25ω).
DC-DC Inductor Selection
Three
key
inductor
parameters
must
be
specified for operation with the MAX16984: inductance
value (L), inductor saturation current (ISAT), and DC
resistance (RDCR). To select the proper inductance
value, the ratio of inductor peak-to-peak AC current to
DC average current (LIR) must be selected. A good
compromise between size and loss is a 35% LIR. The
switching frequency, input voltage, output voltage, and
selected LIR then determine the inductor value as follows:
V
× (VSUPSW − VSENSP )
L = SENSP
VSUPSW × fSW × IOUT × LIR
where VSUPSW, VSENSP, and IOUT are typical
values (such that efficiency is optimum for nominal
operating conditions). Table 4 shows recommended
inductor values at various switching frequencies.
Table 4. Output Inductor and Capacitor Value vs. fSW
fSW (kHz)
L (µH)
2200
2.2
440
10
440
10
MINIMUM COUT (µF)
RECOMMENDED COUT
65
3 x 22µF ceramic*
220
20
*Use only ceramic capacitance when possible.
www.analog.com
13
22µF ceramic
65
22µF ceramic + low-ESR 68µF electrolytic (< 0.25Ω)
130
22µF ceramic + low-ESR 120µF electrolytic (< 0.25Ω)
Analog Devices │ 25
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
DC-DC Diode Selection
USB Loads
USB-Voltage Adjustment
For noncompliant USB loads, the MAX16984 can also
support both a hot insertion and soft start into a USB load
of 2ω || 500µF.
The device requires an external Schottky diode rectifier
as a freewheeling diode. Connect this rectifier close to
the MAX16984 using short PCB traces. In FPWM mode,
the Schottky diode helps minimize efficiency losses by
diverting the inductor current that would otherwise flow
through the low-side MOSFET. Choose a rectifier with a
reverse voltage rating greater than the maximum expected
input voltage (VSUPSW), while minimizing forward-voltage
drop. Use a low forward-voltage-drop Schottky rectifier
to limit the negative voltage at LX. Choose a Schottky
rectifier with a low diode capacitance at the reverse voltage
operating point to minimize EMI caused from the diode
ringing at turn-off.
The precision, all internal, feedback-adjustment circuitry
is designed to be used for adjusting the MAX16984 +5V
DC-DC output voltage higher as the USB load current
increases. This is required in automotive applications that
use a permanently embedded and attached captive cable
from the USB Host in the module, to the user-accessible
USB connectors. These cables can be from 30cm to 3m
in length. As the USB portable load currents increase
for CDP/DCP (1.5A) and iPad (2.1A) applications, these
captive cables experience even higher voltage drops.
Determining System Requirements
The nominal cable resistance (with tolerance) for both
the USB power wire (BUS) and return GND wire should
be determined from the cable manufacturer. In addition,
be sure to include the resistance from any inline or PCB
connectors. Determine the desired operating temperature
range for the application.
A typical application presents a 200mΩ BUS resistance in
the captive cable and also the same 200mΩ in the ground
path. For this application, the detected voltage drop at the
end of a captive cable with a load current of 2A will be
800mV. This voltage drop requires the voltage-adjustment
circuitry of the MAX16984 to adjust the USB +5V and
compensate for the drop in voltage to allow the voltage
at the end of the cable to comply with either the USB 2.0,
USB-IF BC1.2, or Apple requirements.
The MAX16984 is compatible with both USB-compliant
and non-compliant loads. For compliant USB loads, when
a USB device is physically plugged (ATTACHED) into
the USB connector, it is not allowed to pull more than
30mA and must not present a capacitance to GND
of more than 10µF. The device then begins its D+/Dconnection
and
enumeration
process.
After
completion of the CONNECT process, the device can pull
100mA/150mA and must not present a capacitance greater
than 10µF. This is considered the compliant, hot inserted,
USB load of 44ω || 10µF.
Configure USB Output Current Limit
The current that the DC-DC converter is supplying to
the USB load is monitored by the internal current-sense
amplifier (SENSP, SENSN), and the MAX16984 integrates
a configurable USB current-limit threshold. Connect a
resistor from SENSO to GND to set the desired current
limit. See Figure 8. To calculate the RSENSO value:
• Choose desired current limit: ILIMIT
• Calculate resistance required on SENSO:
RSENSO =
1.2
ILIMIT × RSENSE × 0.0025
Note: 0.0025 is SENSO transconductance value,
GSENSO (typ).
Configure DC-DC Output-Voltage Adjustment
The DC-DC output voltage increases linearly as the
voltage on FBMAX increases. To calculate the RFBMAX
value:
• Choose current-sense resistor used for sensing
current (RSENSE).
• Choose the load current to correct for ILOAD.
• Calculate the total cable resistance to correct for
RCABLE.
• Calculate the required voltage (VADJUST) to increase
the DC-DC output voltage.
VADJUST = ILOAD × (RSENSE + RCABLE)
www.analog.com
Analog Devices │ 26
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
2.50
CURRENT LIMIT
2.00
1.75
1200
1100
CURRENT LIMIT
RSENSE = 25mI
SENSP VOLTAGE INCREASE (mV)
2.25
CURRENT LIMIT
RSENSE = 50mI
1.50
1.25
1.00
0.75
0.50
0.25
0
20.0k 18.6k 17.2k 15.8k 14.4k 13.0k 11.6k 10.2k 8.8k 7.4k 6.0k 4.6k
19.3k 17.9k 16.5k 15.1k 13.7k 12.3k 10.9k 9.5k 8.1k 6.7k 5.3k 3.9k
DVSENSP
RFBMAX = 8000I
DVSENSP
RFBMAX = 6000I
DVSENSP
RFBMAX = 4173I
DVSENSP
RFBMAX = 3000I
DVSENSP
RFBMAX = 1500I
1000
900
800
700
600
500
400
300
200
100
0
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4
USB CURRENT = 1.1A (RSENSO = 8727I)
RSENSO (I)
Figure 8. USB Current Limit: RSENSO vs. Current Limit
Figure 10. Increase in SENSP vs. USB Current
SENSP VOLTAGE INCREASE (mV)
The voltage at FBMAX follows the equation below.
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
DVSENSP
RFBMAX = 8000I
DVSENSP
RFBMAX = 6000I
DVSENSP
RFBMAX = 4173I
DVSENSP
RFBMAX = 3000I
DVSENSP
RFBMAX = 1500I
VFBMAX = ILOAD × RSENSE × 0.0025 × RFBMAX
Note: 0.0025 is FBMAX transconductance value,
GFBMAX (typ).
Calculate the RFBMAX resistor, such that at ILOAD, the
DC-DC output is increased by VADJUST.
RFBMAX =
VADJUST + (5.05 × ILOAD × 0.012)
ILOAD × RSENSE × 0.0025 × A SENSP
With this RFBMAX, maximum adjustment occurs as
VFBMAX crosses the internal 1.2V threshold.
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4
USB CURRENT = 2.3A (RSENSO = 4173I)
Figure 9. Increase in SENSP vs. USB Current
• Determine the setting needed for FBPER. This selects
the SENSP Analog Adjustment Gain (ASENSP) to
increase the DC-DC converter for the application and
minimizes/optimizes the DC-DC adjustment range.
See Figure 9 and Figure 10.
VADJUST
≥ 12.5%
5.05V
Then VFBPER = 0V, else VFBPER = 3.3V.
If
VFBPER = 0V → ASENSP = 1.069
VFBPER = 3.3V → ASENSP = 0.535
www.analog.com
Therefore:
VSENSP(MAX) = 1.2 × ASENSP
Tuning of USB Data Lines
USB HS mode requires careful PCB layout with 90Ω
controlled differential-impedance matched traces of equal
lengths with no stubs or test points. For optimal eye
diagram with maximum peaking at the end of the
captive cable, insert a tuning capacitor and tuning inductor
on either side of MAX16984 as close as possible to the
HVD+/- and D+/- pins. These values are layout dependent.
Initial target values are shown in Figure 11. Figure 12 to
Figure 16 show performance of the MAX16984 with and
without tuning for both near and far USB test locations.
Contact Maxim’s applications team for assistance with the
tuning process.
Analog Devices │ 27
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
12nH
2.2nH
MAX16984
6pF
HVD-
D-
HVD+
D+
12nH
2pF
2.2nH
6pF
2pF
DIFFERENTIAL SIGNAL (V)
0.5
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
TIME (x 10^ - 9) s
Figure 14. Tuned Near Eye Diagram (with Data Switch)
0.5
0.5
0.4
0.3
0.2
0.4
0.3
0.2
0.1
0
DIFFERENTIAL SIGNAL, V
DIFFERENTIAL SIGNAL (V)
Figure 11. Tuning of Data Lines
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
-0.1
-0.2
-0.3
-0.4
-0.5
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
TIME (x 10^ - 9) s
Figure 15. Untuned Far Eye Diagram, 3-Meter Cable
0.5
0.5
0.4
0.3
0.2
0.4
0.3
0.2
0.1
0
DIFFERENTIAL SIGNAL, V
DIFFERENTIAL SIGNAL (V)
Figure 12. Near Eye Diagram (with No Switch)
TIME (x 10^ - 9) s
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
-0.3
-0.4
-0.5
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
TIME (x 10^ - 9) s
Figure 13. Untuned Near Eye Diagram (with Data Switch)
www.analog.com
-0.1
-0.2
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
TIME (x 10^ - 9) s
Figure 16. Tuned Far Eye Diagram, 3-Meter Cable
Analog Devices │ 28
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
RC
1MΩ
RD
1.5kΩ
CHARGE-CURRENTLIMIT RESISTOR
DISCHARGE
RESISTANCE
HIGHVOLTAGE
DC
SOURCE
CS
100pF
STORAGE
CAPACITOR
IPEAK (AMPS)
Ir
100%
90%
DEVICE
UNDER
TEST
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
36.8%
10%
0
0
TIME
tRL
tDL
Figure 17. Human Body ESD Test Model
Figure 18. Human Body Current Waveform
USB Data Line Common-Mode Choke
Placement
and require the power to be cycled. The MAX16984 is
characterized for protection to the following limits:
Most automotive applications use a USB-optimized
common-mode choke to mitigate EMI signal from both
leaving and entering the module. Optimal placement for
this EMI choke is directly at the module USB connector.
This common-mode choke does not replace the need for
the tuning inductors previously mentioned.
ESD Protection
The MAX16984 should be placed as close as
possible to the module USB connector for optimal ESD
performance. No external ESD-protection diodes are
required when using the MAX16984. Maxim devices
incorporate ESD-protection structures to protect against
electrostatic discharges encountered during handling
and assembly. The MAX16984 provides additional
protection against static electricity. Maxim’s state-of-theart structures protect against ESD of ±25kV on HVD+
and HVD-. The ESD structures withstand high ESD in
all states: normal operation, shutdown, and powered
down. After an ESD event, the MAX16984 continues to
work without latchup, while other solutions can latch up
www.analog.com
1) ±25kV ISO 10605 Air Gap
2) ±8kV ISO 10605 Contact
3) ±15kV IEC 61000-4-2 Air Gap
4) ±8kV IEC 61000-4-2 Contact
5) ±15kV 330Ω, 330pF Air Gap
6) ±8kV 330Ω, 330pF Contact
Note: All application-level ESD testing is performed using
a MAX16984 evaluation kit.
ESD Test Conditions
ESD performance depends on a variety of conditions.
Contact Maxim for test setup, test methodology, and test
results.
Human Body Model
Figure 17 shows the Human Body Model, and
Figure 18 shows the current waveform it generates when
discharged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of interest,
which is then discharged into the device through a 1.5kΩ
resistor.
Analog Devices │ 29
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
RC
50MΩ TO 100MΩ
RD
330Ω
CHARGE-CURRENTLIMIT RESISTOR
DISCHARGE
RESISTANCE
HIGHVOLTAGE
DC
SOURCE
CS
150pF
STORAGE
CAPACITOR
IPEAK (AMPS)
100%
90%
DEVICE
UNDER
TEST
10%
t
tR = 0.7ns TO 1ns
30ns
60ns
Figure 19. IEC 61000-4-2 ESD Test
Figure 20. IEC 61000-4-2 ESD Generator Current Waveform
IEC 61000-4-2
the ESD withstand voltage measured to this standard
is generally lower than that measured using the Human
Body Model. Figure 20 shows the current waveform for
the ±8kV, IEC 61000-4-2 Level 4, ESD Contact Discharge
test. The Air Gap Discharge test involves approaching
the device with a charged probe. The Contact Discharge
method connects the probe to the device before the probe
is energized.
The IEC 61000-4-2 standard covers ESD testing and
performance of finished equipment. The MAX16984 helps
users design equipment that meet Level 4 of IEC 610004-2. The main difference between tests done using the
Human Body Model and IEC 61000-4-2 is higher peak
current in IEC 61000-4-2. Because series resistance is
lower in the IEC 61000-4-2 ESD test model (Figure 19),
www.analog.com
Analog Devices │ 30
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Typical Operating Circuit
+3.3V USB
I/O VOLTAGE
1µF
IN
100kΩ
MAX16984
D-
6pF
15nH
D+
USB
HOST
CONNECTOR
15nH
HVD-
D-
HVD+
D+
6pF
GND
VBUS
0.1µF
50mΩ
2.2µH
22µF
IN
12kΩ
PGND
SYNC
FOSC
2.2nH
6pF
4.7µF
2.1A
FPWM
DC-DC
SUP
BIAS
BIAS
1µF
LOWVOLTAGE
µC OR ASIC
WITH
INTEGRATED
USB
TRANSCEIVER
EN USB
VBAT
FEEDBACK I LIMIT
4.7µF
REF
to ADC
SENSO
SENSN
CURRENTSENSE AMP
FEEDBACK
ADJUSTMENT
47µF
ENBUCK
ENBUCK
SENSP
FBCAP
3.3V
SUPSW
0.1µF
LX
6pF
2.2nH
USB AUTO DCP, CDP,
iPod, iPad
CHARGER DETECTION
BST
GND
OCI
I/O
I/O
FAULT
CD1
CD0
I/O
CONTROL
AND
DIAGNOSTICS
RSENSO
CSENSO
RFBMAX
CFBMAX
FBMAX
FBPER
10pF
www.analog.com
Analog Devices │ 31
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Ordering Information
PART
MAX16984RAGI/VY+
TEMP RANGE
SPREAD SPECTRUM
-40°C to +125°C
Disabled
PIN-PACKAGE
28 QFND-EP* (SW)
28 QFND-EP* (SW)
MAX16984SAGI/VY+
-40°C to +125°C
Enabled
MAX16984RATI/V+
-40°C to +125°C
Disabled
28 TQFN-EP*
MAX16984SATI/V+
-40°C to +125°C
Enabled
28 TQFN-EP*
MAX16984RACIL/VY+
-40°C to +125°C
Disabled
28 CPQFN-EP* (SW)
28 CPQFN-EP* (SW)
MAX16984SACIL/VY+
-40°C to +125°C
Enabled
MAX16984RACIL/V+
-40°C to +125°C
Disabled
28 CPQFN-EP*
MAX16984SACIL/V+
-40°C to +125°C
Enabled
28 CPQFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive-qualified part.
*EP = Exposed pad.
(SW) = Side wettable.
Tape-and-reel versions available―contact factory for availability.
Chip Information
PROCESS: BiCMOS
www.analog.com
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that
a “+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but the
drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN
NO.
28 QFND-EP
(Side-Wettable)
G2855Y+2
21-0563
90-0375
28 TQFN-EP
T2855+6
21-0140
90-0026
28 CPQFN-EP
CP2844+1
21-100469
90-100204
28 CPQFN-EP
(Side-Wettable)
CP2844Y+1
21-100471
90-100202
Analog Devices │ 32
MAX16984
Automotive High-Current Step-Down Converter with
USB Protection/Host Charger Adapter Emulator
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
0
3/13
Initial release
1
7/13
Corrected values/figures, updated Electrical Characteristics table specs, and clarified
spread-spectrum information
3–6, 11, 12, 17,
19, 20, 22, 27,
28, 31,
2
12/14
Updated Switching Frequency (FOSC, SYNC) section and Typical Operating Circuit
18, 31
3
4/15
Updated Benefits and Features section, added new Note 1 to Absolute Maximum
Ratings and renumbered remaining notes through end of Electrical Characteristics,
updated pins 15 and 16 in Pin Description table, updated Tuning of USB Data Lines
section and Typical Operating Circuit
1–6, 16, 27, 31
4
5/16
Removed future product references
32
5
9/16
Updated Switching Frequency (FOSC, SYNC) section
8
6
5/18
Added new footnote for tape-and-reel versions under Ordering Information table
32
7
2/21
Updated Benefits and Features, Package Thermal Characteristics, Pin Configuration,
Pin Description, Ordering Information, and Package Information
8
3/21
Updated Pin Configuration
DESCRIPTION
—
1, 2, 15, 16, 17
15
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is
assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that
may result from its use. Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are
the property of their respective owners.
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Analog Devices │ 33
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