Datasheet

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MAX16952

36V, 2.2MHz Step-Down Controller

with Low Operating Current

EVALUATION KIT AVAILABLE

19-5789; Rev 4; 10/14

General Description

The MAX16952 is a current-mode, synchronous PWM

step-down controller designed to operate with input volt-

ages from 3.5V to 36V while using only 50μA of quies-

cent current at no load. The switching frequency is

adjustable from 1MHz to 2.2MHz by an external resistor

and can be synchronized to an external clock up to

2.4MHz. The MAX16952 output voltage is pin program-

mable to be either 5V fixed, or adjustable from 1V to 10V.

The wide input voltage range, along with its ability to

operate in dropout during undervoltage transients,

makes it ideal for automotive and industrial applications.

The MAX16952 operates in fixed-frequency PWM mode

and low quiescent current skip mode. It features an

enable logic input, which is compatible up to 42V to dis-

able the device and reduce its shutdown current to

10μA. Protection features include overcurrent limit, over-

voltage, undervoltage, and thermal shutdown with auto-

matic recovery. The device also features a power-good

monitor to ease power-supply sequencing.

The MAX16952 is available in a thermally enhanced

16-pin TSSOP package with an exposed pad, and is

specified for operation over the -40°C to +125°C automo-

tive temperature range.

Applications

Automotive

Industrial

Military

Point of Load

Features

o Wide 3.5V to 36V Input Voltage Range

o 42V Input Transient Tolerance

o High Duty Cycle During Undervoltage Transients

o 1MHz to 2.2MHz Adjustable Switching Frequency

o Adjustable (1V to 10V) Output Voltage with ±2%

Accuracy

o Three Operating Modes

50µA Ultra-Low Quiescent Current Skip Mode

Forced Fixed-Frequency Mode

External Frequency Synchronization

o Lowest BOM Count, Current-Mode Control

Architecture

o Power-Good Output

o Enable Input Compatible from 3.3V Logic Level to

42V

o Current-Limit, Thermal Shutdown, and

Overvoltage Protection

o -40°C to +125°C Automotive Temperature Range

o Automotive Qualified

Ordering Information

PART TEMP RANGE PIN-PACKAGE

MAX16952AUE+ -40°C to +125°C 16 TSSOP-EP*

MAX16952AUE/V+ -40°C to +125°C 16 TSSOP-EP*

/V denotes an automotive qualified part.

Denotes a lead(Pb)-free/RoHS-compliant package.

EP = Exposed pad.

Typical Operating Circuit

MAX16952

FOSC

SGND

BIAS

OUT

FOSC

COMP

SENSE

COMP

FSYNC

PGOOD

COMP1

COMP2

BST

SUP

BAT

BST

PGND

OUT

Summary of content (24 pages)

PAGE 1
EVALUATION KIT AVAILABLE 36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 General Description Features The MAX16952 is a current-mode, synchronous PWM step-down controller designed to operate with input voltages from 3.5V to 36V while using only 50μA of quiescent current at no load. The switching frequency is adjustable from 1MHz to 2.2MHz by an external resistor and can be synchronized to an external clock up to 2.4MHz.
PAGE 2
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Absolute Maximum Ratings SUP and EN to SGND ............................................-0.3V to +42V LX to PGND ..............................................................-1V to +42V BST to LX .................................................................-0.3V to +6V BIAS, FB, PGOOD, FSYNC to SGND .......................-0.3V to +6V DH to LX ...................................................................-0.
PAGE 3
6V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Electrical Characteristics (continued) (VSUP = VEN = 14V, CIN = 10μF, COUT = 94μF, CBIAS = 2.2μF, CBST = 0.1μF, RFOSC = 14.3kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2) PARAMETER Transconductance (from FB to COMP) SYMBOL CONDITIONS MIN TYP MAX UNITS gm,EA 1200 μS Error-Amplifier Output Impedance ROUT,EA 30 MΩ Operating Frequency fSW Minimum On-Time RFOSC = 30.
PAGE 4
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Electrical Characteristics (continued) (VSUP = VEN = 14V, CIN = 10μF, COUT = 94μF, CBIAS = 2.2μF, CBST = 0.1μF, RFOSC = 14.3kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 5
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Typical Operating Characteristics (VSUP = VEN = 14V, CIN = 47μF, COUT = 94μF, CBIAS = 2.2μF, CBST = 0.1μF, RFOSC = 13kΩ, VFB = VBIAS, RBST = 75Ω, TA = +25°C, unless otherwise noted.) STARTUP RESPONSE (SKIP MODE) STARTUP RESPONSE (SKIP MODE) MAX16952 toc01 VSUP MAX16952 toc02 2.2MHz/3.3V 10V/div 10V/div VSUP 0V 2V/div VOUT 2V/div VOUT 0V 2A/div ILOAD 2A/div ILOAD 0A 5V/div VPGOOD 5V/div VPGOOD 0V 2.
PAGE 6
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Typical Operating Characteristics (continued) (VSUP = VEN = 14V, CIN = 47μF, COUT = 94μF, CBIAS = 2.2μF, CBST = 0.1μF, RFOSC = 13kΩ, VFB = VBIAS, RBST = 75Ω, TA = +25°C, unless otherwise noted.) LOAD TRANSIENT (PWM MODE) LOAD TRANSIENT (PWM MODE) MAX16952 toc09 MAX16952 toc08 2.2MHz/3.3V 2.
PAGE 7
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Typical Operating Characteristics (continued) (VSUP = VEN = 14V, CIN = 47μF, COUT = 94μF, CBIAS = 2.2μF, CBST = 0.1μF, RFOSC = 13kΩ, VFB = VBIAS, RBST = 75Ω, TA = +25°C, unless otherwise noted.) OUTPUT RESPONSE TO SLOW RAMP AT SUP (PWM MODE) OUTPUT RESPONSE TO SLOW RAMP AT SUP (SKIP MODE) MAX16952 toc15 MAX16952 toc14 2.2MHz/5V ILOAD = 4A VSUP 10V/div VSUP 0V 5V/div 0V VOUT 2.
PAGE 8
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Typical Operating Characteristics (continued) (VSUP = VEN = 14V, CIN = 47μF, COUT = 94μF, CBIAS = 2.2μF, CBST = 0.1μF, RFOSC = 13kΩ, VFB = VBIAS, RBST = 75Ω, TA = +25°C, unless otherwise noted.) 5.4 5.3 5.2 5.1 5.0 4.9 4.80 4.6 6 11 16 21 26 31 36 4.8 +125°C 2.2MHz/5V 4.2 6 11 16 21 26 31 36 0 10 20 30 40 50 60 70 80 90 100 VSUP (V) VSUP (V) IBAIS (mA) SHUTDOWN CURRENT vs. VSUP SHUTDOWN CURRENT vs.
PAGE 9
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Pin Configuration TOP VIEW SUP 1 EN 2 FOSC 3 + 16 BST 15 DH 14 LX MAX16952 FSYNC 4 13 BIAS SGND 5 12 DL COMP 6 11 PGND FB 7 10 PGOOD 9 OUT EP CS 8 TSSOP Pin Description PIN NAME 1 SUP Input Supply Voltage. SUP is the input voltage to the internal linear regulator. Bypass SUP to PGND with a 1μF minimum value ceramic capacitor. 2 EN Active-High Enable Input. EN is compatible with 5V and 3.
PAGE 10
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Pin Description (continued) PIN NAME 9 OUT 10 PGOOD 11 PGND Power Ground. Connect the input and output filter capacitors’ negative terminals to PGND. Connect PGND externally to SGND at a single point. 12 DL Low-Side Gate-Driver Output. DL swings from VBIAS to PGND. If a resistor is needed between DL and the gate of the MOSFET, the proper resistance value could be provided based on application circuit review result.
PAGE 11
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Functional Diagram SUP EN BST EN LDO BST SWITCH MAX16952 UG DH SGND LX BIAS BUCK CONTROLLER PGOOD REF BIAS FB LG DL PWM EAFB COMP EA REF PGND ILIM OSC FOSC CLK CS ZX FSYNC MODE SYNC CS MODE OUT FBI SGND www.maximintegrated.
PAGE 12
MAX16952 Detailed Description The MAX16952 is a current-mode, synchronous PWM buck controller designed to drive logic-level MOSFETs. The device tolerates a wide input voltage range from 3.5V to 42V and generates an adjustable 1V to 10V or fixed 5V output voltage. This device can operate in dropout mode, making it ideal for automotive and industrial applications with undervoltage transients. The internal switching frequency is adjustable from 1MHz to 2.
PAGE 13
MAX16952 Error Detection and Fault Behavior Several error-detection mechanisms prevent damage to the MAX16952 and the application circuit: • • • • • Overcurrent protection Output overvoltage protection Undervoltage lockout at BIAS Power-good detection of the output voltage Overtemperature protection of the IC Overcurrent Protection The MAX16952 provides cycle-by-cycle current limiting as long as the FB voltage is greater than 0.7V (i.e., 70% of the regulated output voltage).
PAGE 14
MAX16952 exceeds the required load current and discharges when the inductor current is lower, smoothing the voltage across the load. Under soft-overload conditions, when the peak inductor current exceeds the selected current limit, the high-side MOSFET is turned off immediately. The low-side MOSFET is turned on and remains on to let the inductor current ramp down until the next clock cycle.
PAGE 15
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 High-Side Gate-Drive Supply (BST) tON(SKIP) = VOUT VSUPfSW INDUCTOR CURRENT IPK ILOAD = IPK/2 0 ON-TIME TIME Figure 1. Pulse-Skipping/Discontinuous Crossover Point The adaptive driver dead-time allows operation without shoot-through with a wide range of MOSFETs, minimizing delays and maintaining efficiency.
PAGE 16
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 not meet the above condition, then pulse skipping occurs to decrease the effective duty cycle. To avoid this, decrease the switching frequency or lower the input voltage (VSUP). OUT Setting the Output Voltage RFB1 Connect FB to BIAS to enable the fixed step-down controller output voltage (5V), set by a preset, internal resistive voltage-divider connected between the output (OUT) and SGND.
PAGE 17
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 However, if it is necessary, higher inductor values can be selected. The exact inductor value is not critical and can be adjusted to make trade-offs among size, cost, efficiency, and transient response requirements. Table 1 shows a comparison between small and large inductor sizes. Table 1.
PAGE 18
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 and: RDCR = L ⎛ 1 1⎞ ⎜ + ⎟ CEQ ⎝ R1 R2 ⎠ where RCSHL is the required current-sense resistor and RDCR is the inductor’s series DC resistance. Use the typical inductance and RDCR values provided by the inductor manufacturer. Carefully observe the PCB layout guidelines to ensure the noise and DC errors do not corrupt the differential current-sense signals seen by CS and OUT.
PAGE 19
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Input Capacitor The input filter capacitor reduces peak currents drawn from the power source and reduces noise and voltage ripple on the input caused by the circuit’s switching. The input capacitor RMS current requirement (IRMS) is defined by the following equation: IRMS = ILOAD(MAX) VOUT ( VSUP − VOUT ) VSUP I RMS has a maximum value when the input voltage equals twice the output voltage (VSUP = 2VOUT), so IRMS(MAX) = ILOAD(MAX)/2.
PAGE 20
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 by the inductor and output capacitor, resulting in a smaller phase shift and requiring less elaborate erroramplifier compensation than voltage-mode control. A simple single-series resistor (RC) and capacitor (CC) are required to have a stable, high-bandwidth loop in applications where ceramic capacitors are used for output filtering (Figure 5).
PAGE 21
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Therefore: Solving for RC: GAINMOD( fC) × VFB × gm,EA × RC = 1 VOUT Solving for RC: RC = VOUT gm,EA × VFB × GAINMOD( fC) Set the error-amplifier compensation zero formed by RC and CC (fzEA) at the fpMOD.
PAGE 22
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 Both n-channel MOSFETs must be logic-level types with guaranteed on-resistance specifications at VGS = 4.5V. Ensure that the conduction losses at minimum input voltage do not exceed MOSFET package thermal limits or violate the overall thermal budget. Also, ensure that the conduction losses, plus switching losses at the maximum input voltage, do not exceed package ratings or violate the overall thermal budget.
PAGE 23
36V, 2.2MHz Step-Down Controller with Low Operating Current MAX16952 VBAT 5.5V TO 36V C1 0.1μF C2 47μF 50V C11 4.7μF 50V R1 51.1kΩ ±1% 1 SUP 2 VEN EN BST R2 10kΩ 10 VL_IN PGOOD 6 C9 3300pF 4 C8 OPEN R8 13kΩ ±1% LX MAX16952 D2 R5 7.5kΩ DH COMP DL FSYNC PGND CS 3 5 15 N1 FDS8449 16 14 12 L1 1.5μH C4 0.1μF N2 FDS8449 D1 B360B 11 8 R3 0.015Ω ±1% FOSC SGND OUT BIAS 13 9 C6 47μF 6.3V FB 7 C5 47μF 6.3V VOUT 5V C7 2.2μF CONNECT FSYNC TO BIAS FOR FIXED-FREQUENCY PWM MODE.
PAGE 24
36V, 2.