---
type: Analog Component
title: "MAX5026 — 500kHz, 36V Output, SOT23, PWM Step-Up DC-DC Converters"
description: "500kHz, 36V Output, SOT23, PWM Step-Up DC-DC Converters"
resource: "https://www.analog.com/en/products/max5026.html"
tags: ["datasheet", "okf-r12-batch1", "maxim"]
generated: { by: "agentforge/aa0b0641", at: "2026-09-29T20:23:52Z" }
status: draft
sources:
  - id: "datasheet"
    resource: "https://www.analog.com/media/en/technical-documentation/data-sheets/MAX5025-MAX5028.pdf"
    title: "MAX5026 data sheet"
    author: "team:analog-devices"
tables:
  - file: "max5026/tables/table-00-p1-data.csv"
    title: "Ordering Information"
    page: 1
  - file: "max5026/tables/table-01-p2-abs_max.csv"
    title: "Absolute Maximum Ratings"
    page: 2
  - file: "max5026/tables/table-02-p2-spec.csv"
    title: "Electrical Characteristics"
    page: 2
  - file: "max5026/tables/table-03-p8-pin.csv"
    title: "Pin Description"
    page: 8
  - file: "max5026/tables/table-04-p9-data.csv"
    title: "Table 1. Inductor Vendors"
    page: 9
  - file: "max5026/tables/table-05-p10-data.csv"
    title: "Table 2. Schottky Diode Vendors"
    page: 10
  - file: "max5026/tables/table-06-p10-data.csv"
    title: "Table 3. Capacitor Table"
    page: 10
  - file: "max5026/tables/table-07-p12-data.csv"
    title: "Selector Guide"
    page: 12
  - file: "max5026/tables/table-08-p12-data.csv"
    title: "Package Information"
    page: 12
  - file: "max5026/tables/table-09-p13-data.csv"
    title: "Revision History"
    page: 13
figures:
  - file: "max5026/figures/max5026-f000.png"
    caption: ""
    type: "other"
    page: 1
  - file: "max5026/figures/max5026-f002.png"
    caption: ""
    type: "other"
    page: 1
  - file: "max5026/figures/max5026-f003.png"
    caption: ""
    type: "other"
    page: 1
  - file: "max5026/figures/max5026-f008.png"
    caption: "HEAVY-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER"
    type: "characteristic_curve"
    page: 6
  - file: "max5026/figures/max5026-f009.png"
    caption: "LOAD TRANSIENT RESPONSE"
    type: "scope_capture"
    page: 6
  - file: "max5026/figures/max5026-f010.png"
    caption: "MAX5026 FB PIN VOLTAGE vs. TEMPERATURE"
    type: "characteristic_curve"
    page: 6
  - file: "max5026/figures/max5026-f011.png"
    caption: "HEAVY-LOAD SWITCHING WAVEFORM WITH RC FILTER"
    type: "characteristic_curve"
    page: 6
  - file: "max5026/figures/max5026-f012.png"
    caption: "LINE TRANSIENT RESPONSE"
    type: "scope_capture"
    page: 6
  - file: "max5026/figures/max5026-f013.png"
    caption: "MAX5028 FB PIN VOLTAGE vs. TEMPERATURE"
    type: "characteristic_curve"
    page: 6
  - file: "max5026/figures/max5026-f015.png"
    caption: "SWITCH ON-RESISTANCE vs. TEMPERATURE"
    type: "characteristic_curve"
    page: 7
  - file: "max5026/figures/max5026-f016.png"
    caption: "LOAD REGULATION"
    type: "characteristic_curve"
    page: 7
  - file: "max5026/figures/max5026-f018.png"
    caption: "LX LEAKAGE CURRENT vs. TEMPERATURE"
    type: "characteristic_curve"
    page: 7
  - file: "max5026/figures/max5026-f019.png"
    caption: "MAX5026 MAXIMUM LOAD CURRENT vs. INPUT VOLTAGE"
    type: "characteristic_curve"
    page: 7
  - file: "max5026/figures/max5026-f021.png"
    caption: "Figure 1. Functional Diagram"
    type: "block_diagram"
    page: 9
  - file: "max5026/figures/max5026-f023.png"
    caption: "Figure 2. Adjustable 30V Output Circuit"
    type: "application_circuit"
    page: 11
  - file: "max5026/figures/max5026-f024.png"
    caption: "Figure 3. Adjustable 30V Output Circuit with RC Filter"
    type: "application_circuit"
    page: 11
  - file: "max5026/figures/max5026-f027.png"
    caption: "EFFICIENCY vs. LOAD CURRENT (VOUT = 12V)"
    type: "characteristic_curve"
    page: 4
  - file: "max5026/figures/max5026-f028.png"
    caption: "EFFICIENCY vs. LOAD CURRENT (VOUT = 15V)"
    type: "characteristic_curve"
    page: 4
  - file: "max5026/figures/max5026-f029.png"
    caption: "EFFICIENCY vs. LOAD CURRENT (VOUT = 24V)"
    type: "characteristic_curve"
    page: 4
  - file: "max5026/figures/max5026-f030.png"
    caption: "EFFICIENCY vs. LOAD CURRENT (VOUT = 30V)"
    type: "characteristic_curve"
    page: 4
  - file: "max5026/figures/max5026-f031.png"
    caption: "MAX5026 MINIMUM STARTUP VOLTAGE vs. LOAD CURRENT"
    type: "characteristic_curve"
    page: 4
  - file: "max5026/figures/max5026-f032.png"
    caption: "MAX5026/MAX5028 SUPPLY CURRENT vs. SUPPLY VOLTAGE"
    type: "characteristic_curve"
    page: 4
  - file: "max5026/figures/max5026-f033.png"
    caption: "MAX5026 NO LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE"
    type: "characteristic_curve"
    page: 4
  - file: "max5026/figures/max5026-f034.png"
    caption: "MAX5026 SWITCHING FREQUENCY vs. TEMPERATURE"
    type: "characteristic_curve"
    page: 4
  - file: "max5026/figures/max5026-f035.png"
    caption: "SUPPLY CURRENT vs. TEMPERATURE"
    type: "characteristic_curve"
    page: 4
  - file: "max5026/figures/max5026-f036.png"
    caption: "EXITING SHUTDOWN"
    type: "scope_capture"
    page: 5
  - file: "max5026/figures/max5026-f037.png"
    caption: "ENTERING SHUTDOWN"
    type: "scope_capture"
    page: 5
  - file: "max5026/figures/max5026-f038.png"
    caption: "LIGHT-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER"
    type: "scope_capture"
    page: 5
  - file: "max5026/figures/max5026-f039.png"
    caption: "LIGHT-LOAD SWITCHING WAVEFORM WITH RC FILTER"
    type: "scope_capture"
    page: 5
  - file: "max5026/figures/max5026-f040.png"
    caption: "MEDIUM-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER"
    type: "scope_capture"
    page: 5
  - file: "max5026/figures/max5026-f041.png"
    caption: "MEDIUM-LOAD SWITCHING WAVEFORM WITH RC FILTER"
    type: "scope_capture"
    page: 5
  - file: "max5026/figures/max5026-eq01.png"
    caption: "Equation as printed (p. 9)"
    type: equation
    page: 9
  - file: "max5026/figures/max5026-eq02.png"
    caption: "Equation as printed (p. 9)"
    type: equation
    page: 9
  - file: "max5026/figures/max5026-eq03.png"
    caption: "Equation as printed (p. 9)"
    type: equation
    page: 9
  - file: "max5026/figures/max5026-eq04.png"
    caption: "Equation as printed (p. 9)"
    type: equation
    page: 9
  - file: "max5026/figures/max5026-eq05.png"
    caption: "Equation as printed (p. 9)"
    type: equation
    page: 9
agentforge:
  part_number: "MAX5026"
  collection: "okf-r12-batch1"
---

# MAX5026 — 500kHz, 36V Output, SOT23, PWM Step-Up DC-DC Converters

*Datasheet: [MAX5026 data sheet (PDF)](https://www.analog.com/media/en/technical-documentation/data-sheets/MAX5025-MAX5028.pdf)*

### General Description

The MAX5025-MAX5028 constant-frequency, pulsewidth modulating (PWM), low-noise boost converters are intended for low-voltage systems that often need a locally generated high voltage. These devices are capable of generating low-noise, high output voltages required for varactor diode biasing in TV tuners, set-top boxes, and PCI cable modems. The MAX5025MAX5028 operate from as low as 3V and switch at 500kHz.

The constant-frequency, current-mode PWM architecture provides for low output noise that is easy to filter. A 40V lateral DMOS device is used as the internal power switch, making the devices ideal for boost converters up to 36V. The MAX5025/MAX5026 adjustable versions require the use of external feedback resistors to set the output voltage. The MAX5027/MAX5028 offer a fixed 30V output. These devices are available in a small, 6pin SOT23 package.

### Applications

- TV Tuner Power Supply
- Low-Noise Varactor Diode Biasing
- Set-Top Box Tuner Power Supply
- PCI Cable Modem
- Voice-Over-Cable
- LCD Power Supply
- Avalanche Photodiode Biasing

### Typical Operating Circuit

Features

- Input Voltage Range: 3V to 11V (MAX5026/MAX5028) 4.5V to 11V (MAX5025/MAX5027)
- Wide Output Voltage Range: VCC to 36V
- Output Power: 120mW (max)
- User-Adjustable Output Voltage with MAX5025/MAX5026 Using External Feedback Resistors
- Fixed 30V Output Voltage: MAX5027/MAX5028
- Internal 1.3Ω (typ), 40V Switch
- Constant PWM Frequency Provides Easy Filtering in Low-Noise Applications
- 500kHz (typ) Switching Frequency
- 1µA (max) Shutdown Current
- Small, 6-Pin SOT23 Package

### Ordering Information

**Ordering Information** ([table-00-p1-data.csv](max5026/tables/table-00-p1-data.csv), p. 1)

| PART | TEMP RANGE | PIN-PACKAGE |
|---|---|---|
| MAX5025EUT-T | -40°C to +85°C | 6 SOT23-6 |
| MAX5026EUT-T | -40°C to +85°C | 6 SOT23-6 |
| MAX5027EUT-T | -40°C to +85°C | 6 SOT23-6 |
| MAX5028EUT-T | -40°C to +85°C | 6 SOT23-6 |

Selector Guide appears at end of data sheet.

### Pin Configuration

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.

### ABSOLUTE MAXIMUM RATINGS

**Absolute Maximum Ratings** ([table-01-p2-abs_max.csv](max5026/tables/table-01-p2-abs_max.csv), p. 2)

| PARAMETER | RATING |
|---|---|
| V_CC to GND | -0.3V to +12V |
| PGND to GND | -0.1V to +0.1V |
| FB to GND (MAX5025/MAX5026) | -0.3V to (V_CC + 0.3V) |
| FB to GND (MAX5027/MAX5028) | -0.3V to +40V |
| S̅H̅D̅N̅ to GND | -0.3V to (V_CC + 0.3V) |
| LX to GND | -0.3V to +45V |
| Peak LX Current | 600mA |
| Operating Temperature Range | -40°C to +85°C |
| **Continuous Power Dissipation (T_A = +70°C)** |  |
| 6-Pin SOT23 (derate 8.7mW/°C above +70°C) | 695.7mW |
| Junction Temperature | +150°C |
| Storage Temperature Range | -65°C to +165°C |
| Lead Temperature (soldering 10s) | +300°C |

Stresses beyond those listed under 'Absolute Maximum Ratings' may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

### ELECTRICAL CHARACTERISTICS

(VCC = 5V, SHDN = VCC, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)

**Electrical Characteristics** ([table-02-p2-spec.csv](max5026/tables/table-02-p2-spec.csv), p. 2)

| PARAMETER | SYMBOL | CONDITIONS | MIN | TYP | MAX | UNITS |
|---|---|---|---|---|---|---|
| **SUPPLY VOLTAGE** |  |  |  |  |  |  |
| **SUPPLY VOLTAGE** |  |  |  |  |  |  |
| Input Voltage Range | V_CC | MAX5026/MAX5028 | 3.0 |  | 11 | V |
| Input Voltage Range | V_CC | MAX5025/MAX5027 | 4.5 |  | 11 | V |
| Undervoltage Lockout | V_UVLO | Rise/fall, hysteresis = 3mV | 2.25 | 2.65 | 2.95 | V |
| Supply Current | I_CC | MAX5025/MAX5026, FB = 1.4V MAX5027/MAX5028, FB = 35V |  | 350 | 1000 | µA |
| Shutdown Current | I_SHDN | S̅H̅D̅N̅ = GND |  | 0.01 | 1 | µA |
| **BOOST CONVERTER** |  |  |  |  |  |  |
| **BOOST CONVERTER** |  |  |  |  |  |  |
| Switching Frequency | f_SW | MAX5025/MAX5027 | 345 | 500 | 1000 | kHz |
| Switching Frequency | f_SW | MAX5026/MAX5028, V_CC = 3.3V | 410 | 500 | 670 | kHz |
| Line Regulation |  | MAX5025/MAX5027, I_LOAD = 2mA, V_CC = 4.5V to 11V, V_OUT = 30V |  | 0.25 |  | %/V |
| Line Regulation |  | MAX5026/MAX5028, I_LOAD = 0.5mA, V_CC = 3V to 11V, V_OUT = 30V |  | 0.25 |  | %/V |
| Load Regulation |  | MAX5025/MAX5027, V_CC = 5V, I_LOAD = 0 to 4mA, V_OUT = 30V |  | 2.0 |  | % |
| Load Regulation |  | MAX5026/MAX5028, V_CC = 3.3V, I_LOAD = 0 to 1mA, V_OUT = 30V |  | 1.0 |  | % |
| Thermal Shutdown |  |  |  | 140 |  | °C |
| Thermal Shutdown Hysteresis |  |  |  | 2 |  | °C |
| FB Set Point | V_FB | MAX5025, V_CC = 4.5V to 11V | 1.19 | 1.25 | 1.31 | V |
| FB Set Point | V_FB | MAX5027, V_CC = 4.5V to 11V | 28.5 | 30.0 | 31.5 | V |
| FB Set Point | V_FB | MAX5026, V_CC = 3.3V to 11V | 1.212 | 1.25 | 1.288 | V |
| FB Set Point | V_FB | MAX5028, V_CC = 3.3V to 11V | 29.0 | 30 | 31 | V |
| FB Input Bias Current | I_FB | MAX5025/MAX5026, FB = 1V |  | 110 | 310 | nA |
| FB Input Bias Current | I_FB | MAX5027/MAX5028, FB = 30V |  | 100 | 170 | µA |
| Output Voltage Adjustment Range |  | MAX5025/MAX5026 | V_CC + 1 |  | 36 | V |
| **LX OUTPUT** |  |  |  |  |  |  |
| **LX OUTPUT** |  |  |  |  |  |  |
| LX On-Resistance | R_ON | I_LX = 40mA, MAX5026/MAX5028, V_CC = 3V |  | 2.0 | 4.0 | Ω |
| LX On-Resistance | R_ON | I_LX = 40mA, V_CC = 5V |  | 1.3 | 3.0 | Ω |
| LX On-Resistance | R_ON | I_LX = 40mA, V_CC = 11V |  | 1.0 | 2.5 | Ω |
| Switch Current Limit | I_LIM | Note 2 |  | 260 |  | mA |
| LX Leakage Current |  | V_LX = 40V, MAX5025/MAX5026, V_FB = 1.4V |  | 0.01 | 10 | µA |
| LX Leakage Current |  | V_LX = 40V, MAX5027/MAX5028, V_FB = 35V |  | 0.01 | 10 | µA |
| **LOGIC INPUT: S̅H̅D̅N̅** |  |  |  |  |  |  |
| **LOGIC INPUT: S̅H̅D̅N̅** |  |  |  |  |  |  |
| Input Low Level | V_IL |  |  |  | 0.8 | V |
| Input High Level | V_IH |  | 2.4 |  |  | V |
| Input Bias Current |  |  | -1 |  | 1 | µA |

- **Note 1:** All devices are 100% production tested at T<sub>A</sub> = +25°C. All temperature limits are guaranteed by design.

- **Note 2:** Switch current-limit accuracy is typically ±20% and is a function of the input voltage. ILIM = (VIN/5) (260mA).

### Typical Operating Characteristics

MXI

(VCC = 5V, VOUT = 30V, TA = +25°C, unless otherwise noted.)

### Typical Operating Characteristics (continued)

(VCC = 5V, VOUT = 30V, TA = +25°C, unless otherwise noted.)

MAX5026, VCC = 5V, V OUT  = 30V, I LOAD  = 4mA. CIRCUIT OF FIGURE 2

### LOAD TRANSIENT RESPONSE

MAX5026, VCC = 5V, V OUT  = 30V, I LOAD  = 0 TO 4mA. CIRCUIT OF FIGURE 2

### LINE TRANSIENT RESPONSE

MAX5026, VCC = 5V TO 5.2V, V OUT  = 30V, I LOAD  = 1mA. CIRCUIT OF FIGURE 2

(VCC = 5V, VOUT = 30V, TA = +25°C, unless otherwise noted.)

### Pin Description

**Pin Description** ([table-03-p8-pin.csv](max5026/tables/table-03-p8-pin.csv), p. 8)

| NUMBER | NAME | TYPE | DESCRIPTION |
|---|---|---|---|
| 1/1 | PGND |  | Power Ground. Connect directly to local ground plane. Use a star ground configuration for low noise. |
| 2/2 | GND |  | Ground. Connect directly to local ground plane. |
| 3/— | FB |  | Feedback Pin. Reference voltage is approximately 1.25V. Connect resistive-divider tap here. Minimize trace area at FB. See Setting the Output Voltage section. |
| —/3 | FB |  | Feedback Pin. Connect V_OUT to FB for +30V. Internal resistors divide down the output voltage. |
| 4/4 | S̅H̅D̅N̅ |  | Shutdown Pin. Connect to V_CC to enable device. Connect to GND to shut down. |
| 5/5 | V_CC |  | Input Supply Voltage. Bypass with a 4.7µF ceramic capacitor. |
| 6/6 | LX |  | Drain of Internal 40V N-Channel DMOS. Connect inductor/diode to LX. Minimize trace area at this pin to keep EMI down. |

### Detailed Description

The MAX5025-MAX5028 current-mode PWM controllers  operate  in  a  wide  range  of  DC-DC  conversion applications including boost, flyback, and isolated output configurations. These converters provide lownoise, high output voltages making them ideal for varactor diode tuning applications as well as TFT LCD bias.  Other features include shutdown, fixed 500kHz PWM oscillator, and a wide input range: 3V to 11V for MAX5026/MAX5028 and 4.5V to 11V for MAX5025/ MAX5027.

The MAX5025-MAX5028 operate in discontinuous mode in order to reduce the switching noise at the output. Other continuous mode boost converters generate a large voltage spike at the output when the LX switch turns on because there is a conduction path between the output, diode, and switch to ground during the time needed for the diode to turn off.

To reduce the output noise even further, the LX switch turns off by taking 40ns typically to transition from 'ON' to 'OFF.' As a consequence, the positive slew rate of the LX node is reduced and the current from the inductor  does not 'force' the output voltage as hard as would be the case if the LX switch were to turn off more quickly.

### PWM Controller

The heart of the MAX5025-MAX5028 current-mode PWM controllers is a BiCMOS multi-input comparator that  simultaneously processes the output-error signal and switch current signal. The main PWM comparator is  direct  summing,  lacking  a  traditional  error  amplifier and its associated phase shift. The direct summing configuration approaches ideal cycle-by-cycle control over the output voltage since there is no conventional error amp in the feedback path.

The device operates in PWM mode using a fixed-frequency, current-mode operation. The current-mode feedback loop regulates peak inductor current as a function of the output error signal.

### SHDN Input

The SHDN pin provides shutdown control. Connect SHDN to  VCC for  normal operation. To disable the device, connect SHDN to GND.

### Design Procedure

The MAX5025-MAX5028 can operate in a number of DC-DC converter configurations including step-up, single-ended primary inductance converter (SEPIC), and flyback. The following design discussions are limited to step-up,  with  a  complete  circuit  shown  in  the Application Circuits section.

### Setting the Output Voltage

The output voltage of the MAX5027/MAX5028 is fixed at 30V. The output voltage of the MAX5025/MAX5026 is set by two external resistors (R1 and R2, Figure 2 and Figure 3). First select the value of R2 in the 5k Ω to 50k Ω range. R1 is then given by:

![Equation as printed (p. 9)](max5026/figures/max5026-eq01.png)

$$R 1 = R 2 \left( \frac{V_{OUT}}{V_{REF}} - 1 \right)$$

*LaTeX transcription of the equation above, checked against the symbols printed on the page.*

where VREF is 1.25V

### Determining Peak Inductor Current

If  the  boost  converter  remains in the discontinuous mode of operation, then the approximate peak inductor current, ILPEAK, is represented by the formula below:

![Equation as printed (p. 9)](max5026/figures/max5026-eq02.png)

$$I_{LPEAK} \, = \, \sqrt{\frac{2 \, T_{S} \left( V_{OUT} - V_{IN} \right) |_{OUT}}{\eta L}}$$

*LaTeX transcription of the equation above, checked against the symbols printed on the page.*

where TS is the period, VOUT is the output voltage, VIN is the input voltage, IOUT is the output current, and η is the efficiency of the boost converter.

### Table 1. Inductor Vendors

**Table 1. Inductor Vendors** ([table-04-p9-data.csv](max5026/tables/table-04-p9-data.csv), p. 9)

| VENDOR | PHONE | FAX | PART NUMBER OF 47µH INDUCTOR |
|---|---|---|---|
| Coilcraft | 847-639-6400 | 847-639-1469 | DT1608C-473 |
| Sumida | 847-545-6700 | 847-545-6720 | CDRH4D28-470 |
| Toko | 847-297-0070 | 847-699-7864 | A915BY-470M |

### Determining the Inductor Value

47µH is the recommended inductor value when the output voltage is 30V and the input voltage is 5V. In general,  the  inductor  should  have  a  current  rating  greater than the current-limit value.  For example, the inductor's current rating should be greater than 150mA to support a 4mA output current. Equivalent series resistance (ESR) should be below 1 Ω for  reasonable efficiency. Due to the MAX5025-MAX5028's high switching frequency, inductors with a ferrite core or equivalent are recommended. Powdered iron cores are not recommended due to their high losses at frequencies over 500kHz. Table 1 shows a list of vendors and 47µH inductor parts.

For 4mA output current and output voltages other than 30V, the inductor can be simply scaled in value according to the following formula:

![Equation as printed (p. 9)](max5026/figures/max5026-eq03.png)

$$\mathbf L = \frac{( 47 \mu H ) \left( V_{OUT} - V_{IN} \right)}{( 25 V )}$$

*LaTeX transcription of the equation above, checked against the symbols printed on the page.*

Use the following formula to calculate the upper bound of  the  inductor  value  at  different  output  voltages  and output currents. This is the maximum inductance value for discontinuous mode operation.

![Equation as printed (p. 9)](max5026/figures/max5026-eq04.png)

$$L_{UPPER} = \frac{V_{IN}^{2} \left( V_{OUT} - V_{IN} \right) T_{S} \eta}{2 \, I_{OUT} \, V_{OUT}^{2}}$$

*LaTeX transcription of the equation above, checked against the symbols printed on the page.*

Calculate the lower bound, LLOWER, for the acceptable inductance value using the following formula, which will allow the maximum output current to be delivered without reaching the peak current limit:

![Equation as printed (p. 9)](max5026/figures/max5026-eq05.png)

$$L_{LOWER} = \frac{2 T_S \left(V_{OUT} - V_{IN}\right) I_{OUT}}{\eta \left(\frac{V_{IN}}{5} \left(260mA\right)\right)^2}$$

*LaTeX transcription of the equation above, checked against the symbols printed on the page.*

Notice that the switch current limit, (VIN/5)(260mA), is a function of the input voltage, VIN. The current rating of the inductor should be greater than the switch current limit.

For a design in which VIN = 5V, VOUT = 30V, IOUT = 4mA, η = 0.5, and TS = 2µs,

LUPPER = 87µH

and

LLOWER = 12µH.

For a worst-case scenario in which VIN = 4.75V, VOUT = 29V, IOUT = 4.4mA, η = 0.5, and TS = 1.25µs,

LUPPER = 46µH

and

LLOWER = 9µH.

The choice of 47µH as the recommended inductance value is reasonable given the worst-case scenario above. In general, the higher the inductance, the lower the switching noise. Load regulation is also better with higher inductance.

### Diode Selection

The MAX5025-MAX5028's high switching frequency demands a high-speed rectifier. Schottky diodes are recommended for most applications because of their fast recovery time and low forward-voltage drop. Ensure that the diode's peak current rating is greater than or equal to the peak inductor current. Also, the diode reverse breakdown voltage must be greater than VOUT. Table 2 lists diode vendors.

**Table 2. Schottky Diode Vendors** ([table-05-p10-data.csv](max5026/tables/table-05-p10-data.csv), p. 10)

| VENDOR | PHONE | FAX | PART NUMBERS |
|---|---|---|---|
| Comchip | 510-657-8671 | 510-657-8921 | CDBS1045 |
| Panasonic | 408-942-2912 | 408-946-9063 | MA2Z785 |
| ST-Microelectronics | 602-485-6100 | 602-486-6102 | TMMBAT48 |
| Vishay-Telefunken | 402-563-6866 | 402-563-6296 | BAS382 |
| Zetex | 631-360-2222 | 631-360-8222 | ZHCS500 |

### Table 3. Capacitor Table

**Table 3. Capacitor Table** ([table-06-p10-data.csv](max5026/tables/table-06-p10-data.csv), p. 10)

| COMPANY | PHONE | FAX | PART NUMBERS |
|---|---|---|---|
| Murata | 814-237-1431 | 814-238-0490 | GRM42-2X7R105K050AD (1µF capacitor) |
| Murata | 814-237-1431 | 814-238-0490 | GRM32-1210R71C475R (4.7µF capacitor) |
| Taiyo Yuden | 408-573-4150 | 408-573-4159 | UMK325BJ105KH (1µF capacitor) |
| Taiyo Yuden | 408-573-4150 | 408-573-4159 | EMK316BJ475ML (4.7µF capacitor) |
| TDK | 847-803-6100 | 847-803-6296 | C3225X7R1H155K (1.5µF capacitor) |
| TDK | 847-803-6100 | 847-803-6296 | C3225X7R1H105K (1µF capacitor) |

### Capacitor Selection

### Output Filter Capacitor

The output filter capacitor should be 1µF or greater. To achieve low output ripple, a capacitor with low ESR, low ESL, and high capacitance value should be selected.

For very low output ripple applications, the output of the boost converter can be followed by an RC filter to further reduce the ripple. Figure 3 shows a 100 Ω , 1µF filter  used to reduce the switching output ripple to 1mVp-p.

X7R ceramic capacitors are better for this boost application because of their low ESR and tighter tolerance over temperature than the Y5V ceramic capacitors. Table 3 below lists manufacturers of recommended capacitors.

### Input Capacitor

Bypass VCC with a 4.7µF ceramic capacitor as close to the IC as is practical.

### Applications Information

### Layout Considerations

The MAX5025-MAX5028 switch at high speed, mandating careful attention to layout for optimum performance. Protect sensitive analog grounds by using a star  ground configuration. Minimize ground noise by connecting GND, PGND, the input bypass-capacitor ground lead, and the output-filter ground lead to a single point (star ground configuration). Also, minimize

trace lengths to reduce stray capacitance, trace resistance, and radiated noise. The trace between the output voltage-divider (MAX5025/MAX5026) and the FB pin must be kept short, as well as the trace between GND and PGND.

### Inductor Layout

The shielded drum type inductors have a small air gap around the top and bottom periphery. The incident fringing magnetic field from this air gap to the copper plane on the PC board tends to reduce efficiency. This is a result of the induced eddy currents on the copper plane. To minimize this effect, avoid laying out any copper planes under the mounting area of these inductors.

### 30V Boost Application Circuit

Figures 2 and 3 show the MAX5025/MAX5026 operating in a 30V boost application. Figure 3 has an RC filter to  reduce noise at the output. These circuits provide output currents greater than 4mA with an input voltage of  5V  or  greater.  They  are  designed  by  following  the Design Procedure section. Operating characteristics of these circuits are shown in the Typical Operating Characteristics section.


### Selector Guide

**Selector Guide** ([table-07-p12-data.csv](max5026/tables/table-07-p12-data.csv), p. 12)

| PART | OUTPUT | FREQUENCY TOLERANCE | FB SET POINT TOLERANCE | INPUT VOLTAGE |
|---|---|---|---|---|
| MAX5025 | Adjustable | -31% to +100% | ±5% | 4.5V to 11V |
| MAX5026 | Adjustable | -18% to +34% | ±3% | 3V to 11V |
| MAX5027 | Fixed 30V | -31% to +100% | ±5% | 4.5V to 11V |
| MAX5028 | Fixed 30V | -18% to +34% | ±3% | 3V to 11V |

### Chip Information

TRANSISTOR COUNT: 365 PROCESS: BiCMOS

### Package Information

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages .

**Package Information** ([table-08-p12-data.csv](max5026/tables/table-08-p12-data.csv), p. 12)

| PACKAGE TYPE | PACKAGE CODE | DOCUMENT NO. |
|---|---|---|
| 6 SOT23 | S8-2 | 21-0058 |

### Revision History

**Revision History** ([table-09-p13-data.csv](max5026/tables/table-09-p13-data.csv), p. 13)

| REVISION NUMBER | REVISION DATE | DESCRIPTION | PAGES CHANGED |
|---|---|---|---|
| 0 | 10/01 | Initial release | — |
| 1 | 12/01 | Released the MAX5027 | 1 |
| 2 | 3/09 | Revised the Absolute Maximum Ratings section. | 2 |

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

## Additional Figures

![other (p. 1)](max5026/figures/max5026-f000.png)

![other (p. 1)](max5026/figures/max5026-f002.png)

![other (p. 1)](max5026/figures/max5026-f003.png)

![HEAVY-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER](max5026/figures/max5026-f008.png)

*HEAVY-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER*

![LOAD TRANSIENT RESPONSE](max5026/figures/max5026-f009.png)

*LOAD TRANSIENT RESPONSE*

![MAX5026 FB PIN VOLTAGE vs. TEMPERATURE](max5026/figures/max5026-f010.png)

*MAX5026 FB PIN VOLTAGE vs. TEMPERATURE*

![HEAVY-LOAD SWITCHING WAVEFORM WITH RC FILTER](max5026/figures/max5026-f011.png)

*HEAVY-LOAD SWITCHING WAVEFORM WITH RC FILTER*

![LINE TRANSIENT RESPONSE](max5026/figures/max5026-f012.png)

*LINE TRANSIENT RESPONSE*

![MAX5028 FB PIN VOLTAGE vs. TEMPERATURE](max5026/figures/max5026-f013.png)

*MAX5028 FB PIN VOLTAGE vs. TEMPERATURE*

![SWITCH ON-RESISTANCE vs. TEMPERATURE](max5026/figures/max5026-f015.png)

*SWITCH ON-RESISTANCE vs. TEMPERATURE*

![LOAD REGULATION](max5026/figures/max5026-f016.png)

*LOAD REGULATION*

![LX LEAKAGE CURRENT vs. TEMPERATURE](max5026/figures/max5026-f018.png)

*LX LEAKAGE CURRENT vs. TEMPERATURE*

![MAX5026 MAXIMUM LOAD CURRENT vs. INPUT VOLTAGE](max5026/figures/max5026-f019.png)

*MAX5026 MAXIMUM LOAD CURRENT vs. INPUT VOLTAGE*

![Figure 1. Functional Diagram](max5026/figures/max5026-f021.png)

*Figure 1. Functional Diagram*

![Figure 2. Adjustable 30V Output Circuit](max5026/figures/max5026-f023.png)

*Figure 2. Adjustable 30V Output Circuit*

![Figure 3. Adjustable 30V Output Circuit with RC Filter](max5026/figures/max5026-f024.png)

*Figure 3. Adjustable 30V Output Circuit with RC Filter*

![EFFICIENCY vs. LOAD CURRENT (VOUT = 12V)](max5026/figures/max5026-f027.png)

*EFFICIENCY vs. LOAD CURRENT (VOUT = 12V)*

![EFFICIENCY vs. LOAD CURRENT (VOUT = 15V)](max5026/figures/max5026-f028.png)

*EFFICIENCY vs. LOAD CURRENT (VOUT = 15V)*

![EFFICIENCY vs. LOAD CURRENT (VOUT = 24V)](max5026/figures/max5026-f029.png)

*EFFICIENCY vs. LOAD CURRENT (VOUT = 24V)*

![EFFICIENCY vs. LOAD CURRENT (VOUT = 30V)](max5026/figures/max5026-f030.png)

*EFFICIENCY vs. LOAD CURRENT (VOUT = 30V)*

![MAX5026 MINIMUM STARTUP VOLTAGE vs. LOAD CURRENT](max5026/figures/max5026-f031.png)

*MAX5026 MINIMUM STARTUP VOLTAGE vs. LOAD CURRENT*

![MAX5026/MAX5028 SUPPLY CURRENT vs. SUPPLY VOLTAGE](max5026/figures/max5026-f032.png)

*MAX5026/MAX5028 SUPPLY CURRENT vs. SUPPLY VOLTAGE*

![MAX5026 NO LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE](max5026/figures/max5026-f033.png)

*MAX5026 NO LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE*

![MAX5026 SWITCHING FREQUENCY vs. TEMPERATURE](max5026/figures/max5026-f034.png)

*MAX5026 SWITCHING FREQUENCY vs. TEMPERATURE*

![SUPPLY CURRENT vs. TEMPERATURE](max5026/figures/max5026-f035.png)

*SUPPLY CURRENT vs. TEMPERATURE*

![EXITING SHUTDOWN](max5026/figures/max5026-f036.png)

*EXITING SHUTDOWN*

![ENTERING SHUTDOWN](max5026/figures/max5026-f037.png)

*ENTERING SHUTDOWN*

![LIGHT-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER](max5026/figures/max5026-f038.png)

*LIGHT-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER*

![LIGHT-LOAD SWITCHING WAVEFORM WITH RC FILTER](max5026/figures/max5026-f039.png)

*LIGHT-LOAD SWITCHING WAVEFORM WITH RC FILTER*

![MEDIUM-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER](max5026/figures/max5026-f040.png)

*MEDIUM-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER*

![MEDIUM-LOAD SWITCHING WAVEFORM WITH RC FILTER](max5026/figures/max5026-f041.png)

*MEDIUM-LOAD SWITCHING WAVEFORM WITH RC FILTER*